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Fermentation, Volume 7, Issue 2 (June 2021) – 55 articles

Cover Story (view full-size image): Paraburkholderia sp. SOS3 is a plant-growth-promoting bacterium isolated from sugarcane soils in Queensland, Australia. In this study, we developed an efficient strategy to produce a commercial-scale sustainable bioinoculant. The beneficial effects of SOS3 were validated in seeds. Proteome analysis of SOS3 cultures provided new insights into the metabolic pathways linked to plant-growth promotion. Still, further research is needed to explore the mechanisms that are responsible for the observed results. View this paper.
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Article
Growth Enhancement Facilitated by Gaseous CO2 through Heterologous Expression of Reductive Tricarboxylic Acid Cycle Genes in Escherichia coli
Fermentation 2021, 7(2), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020098 - 18 Jun 2021
Viewed by 754
Abstract
The enzymatic mechanisms of carbon fixation by autotrophs, such as the reductive tricarboxylic acid cycle (rTCA), have inspired biotechnological approaches to producing bio-based chemicals directly through CO2. To explore the possibility of constructing an rTCA cycle in Escherichia coli and to [...] Read more.
The enzymatic mechanisms of carbon fixation by autotrophs, such as the reductive tricarboxylic acid cycle (rTCA), have inspired biotechnological approaches to producing bio-based chemicals directly through CO2. To explore the possibility of constructing an rTCA cycle in Escherichia coli and to investigate their potential for CO2 assimilation, a total of ten genes encoding the key rTCA cycle enzymes, including α-ketoglutarate:ferredoxin oxidoreductase, ATP-dependent citrate lyase, and fumarate reductase/succinate dehydrogenase, were cloned into E. coli. The transgenic E. coli strain exhibited enhanced growth and the ability to assimilate external inorganic carbon with a gaseous CO2 supply. Further experiments conducted in sugar-free medium containing hydrogen as the electron donor and dimethyl sulfoxide (DMSO) as the electron acceptor proved that the strain is able to undergo anaerobic respiration, using CO2 as the major carbon source. The transgenic stain demonstrated CO2-enhanced growth, whereas the genes involved in chemotaxis, flagellar assembly, and acid-resistance were upregulated under the anaerobic respiration. Furthermore, metabolomic analysis demonstrated that the total concentrations of ATP, ADP, and AMP in the transgenic strain were higher than those in the vector control strain and these results coincided with the enhanced growth. Our approach offers a novel strategy to engineer E. coli for assimilating external gaseous CO2. Full article
(This article belongs to the Special Issue Carboxylic Acid Production 2.0)
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Article
Effect of Aeration on Yeast Community Structure and Volatile Composition in Uninoculated Chardonnay Wines
Fermentation 2021, 7(2), 97; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020097 - 11 Jun 2021
Cited by 1 | Viewed by 1156
Abstract
Uninoculated wines are regarded as having improved mouthfeel and texture and more complex flavor profiles when compared to wines inoculated with commercial S. cerevisiae strains. Uninoculated fermentation involves a complex microbial succession of yeasts and bacteria during fermentation. Microbial population dynamics are affected [...] Read more.
Uninoculated wines are regarded as having improved mouthfeel and texture and more complex flavor profiles when compared to wines inoculated with commercial S. cerevisiae strains. Uninoculated fermentation involves a complex microbial succession of yeasts and bacteria during fermentation. Microbial population dynamics are affected by several factors that can ultimately determine if a particular species or strain contributes to wine aroma and flavor. In this work, we have studied the effect of aeration, a common winemaking practice, on the yeast microbiota during uninoculated Chardonnay wine fermentation. The timing of aeration and then aeration intensity were evaluated across two successive vintages. While the timing of aeration significantly impacted fermentation efficiency across oxygen treatments, different levels of aeration intensity only differed when compared to the non-aerated control ferments. Air addition increased the viable cell population size of yeast from the genera Hanseniaspora, Lachancea, Metschnikowia and Torulaspora in both vintages. While in 2019, a high relative abundance was found for Hanseniaspora species in aerated ferments, in 2020, T. delbrueckii was visibly more abundant than other species in response to aeration. Accompanying the observed differences in yeast community structure, the chemical profile of the finished wines was also different across the various aeration treatments. However, excessive aeration resulted in elevated concentrations of ethyl acetate and acetic acid, which would likely have a detrimental effect on wine quality. This work demonstrates the role of aeration in shaping yeast population dynamics and modulating a volatile profile in uninoculated wines, and highlights the need for careful air addition to avoid a negative sensory impact on wine flavor and aroma. Full article
(This article belongs to the Special Issue Non-Saccharomyces Yeasts as Aroma Enhancers in Fermented Products)
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Article
Incorporation of Fermented Brewers Spent Grain in the Production of Sourdough Bread
Fermentation 2021, 7(2), 96; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020096 - 10 Jun 2021
Viewed by 801
Abstract
The utilisation of food production by-products back into food production within a circular food economy is one of the driving examples to improve sustainability within the food industry. Brewers spent grain is the most abundant by-product from the brewing industry, with currently most [...] Read more.
The utilisation of food production by-products back into food production within a circular food economy is one of the driving examples to improve sustainability within the food industry. Brewers spent grain is the most abundant by-product from the brewing industry, with currently most of it being used as animal feed. In this study, we utilised brewers spent grain as a substrate in a solid-state fermentation in order to produce a Type-3 sourdough culture. Sourdough bread is becoming increasingly popular throughout the western world. The use of fermented brewers spent grain in the production of sourdough bread yielded sourdough bread that was acceptable by consumers. We also investigated the production and presence of the main organic acids in sourdough during the proofing process and the baking process. The baking trials showed that there was a reduction in both lactic and acetic acid content during the actual baking process. The reduction in the concentration of both organic acids appears to be at the heart of the observation that for both organic acids, there is typically a lower concentration in the crust compared to the crumb of the sourdough breads, which was observed in our sourdough breads and those commercially available. Full article
(This article belongs to the Special Issue Innovations in Sourdough Bread Making)
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Article
Improvement of Enantiomeric l-Lactic Acid Production from Mixed Hexose-Pentose Sugars by Coculture of Enterococcus mundtii WX1 and Lactobacillus rhamnosus SCJ9
Fermentation 2021, 7(2), 95; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020095 - 10 Jun 2021
Viewed by 613
Abstract
Among 39 pentose-utilizing lactic acid bacteria (LAB) selected from acid-forming bacteria from the midgut of Eri silkworm, the isolate WX1 was selected with the highest capability to produce optically pure l-lactic acid (l-LA) from glucose, xylose and arabinose with furfural-tolerant [...] Read more.
Among 39 pentose-utilizing lactic acid bacteria (LAB) selected from acid-forming bacteria from the midgut of Eri silkworm, the isolate WX1 was selected with the highest capability to produce optically pure l-lactic acid (l-LA) from glucose, xylose and arabinose with furfural-tolerant properties. The isolate WX1 was identified as Enterococcus mundtii based on 16S rDNA sequence analysis. The conversion yields of l-LA from glucose and xylose by E. mundtii WX1 were 0.97 and 0.68 g/g substrate, respectively. Furthermore, l-LA production by E. mundtii WX1 in various glucose-xylose mixtures indicated glucose repression effect on xylose consumption. The coculture of E. mundtii WX1 and Lactobacillus rhamnosus SCJ9, a homofermentative LAB capable of producing l-LA from glucose clearly showed an improvement of l-LA production from 30 g/L total glucose-xylose (6:4). The results from Plackett–Burman design (PBD) indicated that Tween 80, MnSO4 and yeast extract (YE) were three medium components that significantly influenced (p < 0.05) l-LA production using the coculture strategy in the presence of 2 g/L furfural. Optimal concentrations of these variables revealed by central composite design (CCD) and response surface methodology (RSM) were 20.61 g/L YE, 1.44 g/L Tween 80 and 1.27 g/L MnSO4. Based on the optimized medium with 30 g/L total glucose-xylose (6:4), the maximum experimental l-LA value of 23.59 g/L reflecting 0.76 g/g substrate were achieved from 48 h fermentation at 37 °C. l-LA produced by coculture cultivated under standard MRS medium and new optimized conditions were 1.28 and 1.53 times higher than that obtained from single culture by E. mundtii WX1, respectively. This study provides the foundations for practical applications of coculture in bioconversion of lignocellulose particularly glucose-xylose-rich corn stover to l-LA. Full article
(This article belongs to the Special Issue Lactic Acid Fermentation and the Colours of Biotechnology 3.0)
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Article
Optimal Control Applied to Oenological Management of Red Wine Fermentative Macerations
Fermentation 2021, 7(2), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020094 - 10 Jun 2021
Viewed by 717
Abstract
The management of wineries for industrial red winemaking is limited by the capacity and availability of fermentation tanks over the harvest season. The winemakers aim to optimize the wine quality, the fermentative maceration length, and the fermentation tank’s productive cycle simultaneously. Maceration in [...] Read more.
The management of wineries for industrial red winemaking is limited by the capacity and availability of fermentation tanks over the harvest season. The winemakers aim to optimize the wine quality, the fermentative maceration length, and the fermentation tank’s productive cycle simultaneously. Maceration in varietal wine production is carried out until a specific sugar content (digging-out point) is attained, finishing before alcoholic fermentation. Winemakers have found that by trial and error handling of the digging-out point, they can improve the winery capacity and production cost. In this work, we develop an optimal control problem for managing the digging-out point considering two objectives associated with process efficiency and costs. A good compromise between these objectives was found by applying multi-criteria decision-making (MCDM) techniques and the knee point. Two control strategies were compared: free nutrition and traditional nutrition. TOPSIS and LINMAP algorithms were used to choose the most suitable strategy that coincided with the knee point. The preferred option was nitrogen addition only at the beginning of fermentation (6.6–10.6 g/hL of DAP) and a high fermentation temperature (30 °C), yielding the desired digging-out point with a small error (6–9 g/L). Full article
(This article belongs to the Special Issue Control of Wine Fermentation)
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Article
Microbial Composition of Fermented Korean Soy Paste (Doenjang) Prepared by Adding Different Herbs during Fermentation
Fermentation 2021, 7(2), 93; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020093 - 10 Jun 2021
Cited by 1 | Viewed by 780
Abstract
The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by [...] Read more.
The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by 16S rRNA metagenomic analyses. The β-diversity statistics indicated clear distinctions in the doenjang microbiota after the addition of herbs. A microbial composition analysis revealed that Tetragenococcus was among the dominant genera in the four doenjang groups, with a relatively higher abundance in the Korean mint group. In the Peppermint and Korean mint doenjang groups, the levels of undesirable microbes, such as opportunistic pathogens belonging to the genera Sphingobacterium and Pantoea, were significantly reduced. Additionally, other desirable microbes that are known to exhibit beneficial properties and produce bioactive compounds, such as Saccharopolyspora and Buttiauxella, were present at significantly higher levels. Significant negative correlations between members of the Bacillaceae and Halomonadaceae, Lactobacillaceae and Tissierellaceae, and the Lacobacillaceae and Erwiniaceae families were observed, indicating possible antagonistic relationships. Taken together, our results demonstrated that the incorporation of herbs, particularly Peppermint and Korean mint, during doenjang fermentation resulted in significant shifts in the microbial composition and could be utilized for beneficial effect on its fermentation. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites 3.0)
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Article
Impact of Commercial Yeasts on Phenolic Profile of Plavac Mali Wines from Croatia
Fermentation 2021, 7(2), 92; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020092 - 05 Jun 2021
Viewed by 817
Abstract
Wine quality is influenced by the presence of over 500 different chemical compounds, with polyphenols having a crucial role in color intensity and tonality, astringency, mouthfeel, and overall impression formation, especially in red wine production. Their concentrations in wine can vary notably depending [...] Read more.
Wine quality is influenced by the presence of over 500 different chemical compounds, with polyphenols having a crucial role in color intensity and tonality, astringency, mouthfeel, and overall impression formation, especially in red wine production. Their concentrations in wine can vary notably depending on the grape variety, the temperature and the length of maceration process, aging duration, and yeast selection. Therefore, in this work, the main goal was to determine the influence of five commercially available Saccharomyces yeasts provided from Lallemand, France and AEB, Italy, on the phenolic compound composition and chromatic parameters of Plavac mali wines produced from the grapes from coastal Dalmatia, grown at two different micro-locations. The achieved results pointed out the marked difference in individual polyphenol compound adsorption between tested yeasts. Fermol Super 16 was the one with the lowest and Lalvin D21 the strongest adsorption ability, regardless of vine growing location. These differences can be explained by the content of some anthocyanins (delphinidin and petunidin-3-O-glucoside) and gallic acid, and some flavan-3-ols. Tested strains also influenced wine color intensity, pointing out the possibility of modulating the style of a Plavac mali by the use of commercial yeasts. Full article
(This article belongs to the Special Issue Saccharomyces cerevisiae Strains and Fermentation)
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Article
Valorization of Bread Waste to a Fiber- and Protein-Rich Fungal Biomass
Fermentation 2021, 7(2), 91; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020091 - 03 Jun 2021
Cited by 2 | Viewed by 652
Abstract
Filamentous fungi can be used for the valorization of food waste as a value-added product. The goal of this study was the valorization of bread waste through fungal cultivation and the production of value-added products. The fungal cultivation was verified for upscaling from [...] Read more.
Filamentous fungi can be used for the valorization of food waste as a value-added product. The goal of this study was the valorization of bread waste through fungal cultivation and the production of value-added products. The fungal cultivation was verified for upscaling from shake flasks to a bench-scale bioreactor (4.5 L) and a pilot-scale bioreactor (26 L). The fungus showed the ability to grow without any additional enzymes or nutrients, and it was able to consume a bread concentration of 4.5% (w/v) over 48 h. The biomass concentration in the shake flasks was 4.1 g/L at a 2.5% bread concentration, which increased to 22.5 g/L at a 15% bread concentration. The biomass concentrations obtained after 48 h of cultivation using a 4.5% bread concentration were 7.2–8.3 and 8.0 g/L in 4.5 and 26 L bioreactors, respectively. Increasing the aeration rate in the 4.5 L bioreactor decreased the amount of ethanol produced and slightly reduced the protein content of the fungal biomass. The initial protein value in the bread was around 13%, while the protein content in the harvested fungal biomass ranged from 27% to 36%. The nutritional value of the biomass produced was evaluated by analyzing the amino acids and fatty acids. This study presents the valorization of bread waste through the production of a protein- and fatty-acid-rich fungal biomass that is simultaneously a source of microfibers. Full article
(This article belongs to the Special Issue Biodegradation in Fermentation)
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Article
Development of Probiotic Almond Beverage Using Lacticaseibacillus rhamnosus GR-1 Fortified with Short-Chain and Long-Chain Inulin Fibre
Fermentation 2021, 7(2), 90; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020090 - 03 Jun 2021
Cited by 1 | Viewed by 988
Abstract
Plant-based beverages are growing in popularity due to the rise of vegetarianism and other health trends. A probiotic almond beverage that combines the properties of almonds, inulin, and Lacticaseibacillusrhamnosus GR-1 may meet the demand for a non-dairy health-promoting food. The purpose of [...] Read more.
Plant-based beverages are growing in popularity due to the rise of vegetarianism and other health trends. A probiotic almond beverage that combines the properties of almonds, inulin, and Lacticaseibacillusrhamnosus GR-1 may meet the demand for a non-dairy health-promoting food. The purpose of this study was to investigate the viability of L. rhamnosus GR-1 and pH in five fermented almond beverage samples, supplemented with either 2% or 5% (w/v) short-chain or long-chain inulin over 9 h of fermentation and 30 days of refrigerated storage. All almond beverage samples achieved a mean viable count of at least 107 CFU/mL during 9h of fermentation and 30 days of refrigerated storage. The probiotic almond beverage supplemented with 2% (w/v) short-chain inulin had a significantly higher mean microbial count (p = 0.048) and lower pH (p < 0.001) throughout fermentation, while the control and the long-chain inulin treatments had the lowest viable counts and acidity, respectively. This study shows that the addition of short-chain and long-chain inulin had no adverse effects on the viability of L. rhamnosus GR-1. Therefore, the probiotic almond beverage has the potential to be a valid alternative to dairy-based probiotic products. Full article
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Communication
Biological Stoichiometric Analysis during Substrate Utilization and Secondary Metabolite Production by Non-Saccharomyces Yeasts Using Grape Pomace Extract as Fermentation Medium
Fermentation 2021, 7(2), 89; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020089 - 02 Jun 2021
Viewed by 1287
Abstract
The emerging interest in the search for alternatives to synthetic preservatives has led to various successful research studies exploring the use of yeasts as potential biological control agents and producers of biopreservatives. The findings that yeasts could be used as producers of biopreservatives [...] Read more.
The emerging interest in the search for alternatives to synthetic preservatives has led to various successful research studies exploring the use of yeasts as potential biological control agents and producers of biopreservatives. The findings that yeasts could be used as producers of biopreservatives lacked some engineering considerations regarding cost-effective process design for scale-up, although partial process optimization using renewable agro-waste has been achieved. This study investigated the biological stoichiometry and bioenergetic parameters during yeast growth and secondary metabolites production i.e., biopreservatives from non-Saccharomyces yeasts using grape pomace extract (GPE), a type of agro-waste, as a fermentation medium. This was achieved by reconfirming the optimum production conditions previously found for Candida pyralidae Y1117, Pichia kluyveri Y1125, and Pichia kluyveri Y1164 in GPE broth as a fermentation medium, conditions under which a high amount of yeast cells were obtained. High-density cell cultures were produced, from which the yeast cell pellets were harvested, dried, and combusted for the determination of elemental analysis, heat of combustion, biological stoichiometry, and bioenergetic parameters. This work generated biological stoichiometric models and bioenergetics information that could assist in the design of yeast biochemical conversion system when GPE is used as fermentation medium, thereby, addressing the biochemical engineering aspects that were lacking in a previous biopreservative production study using Candida pyralidae Y1117, Pichia kluyveri Y1125, and Pichia kluyveri Y1164. Full article
(This article belongs to the Special Issue Enological Repercussions of Non-Saccharomyces Species 3.0)
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Article
Aeration and Stirring in Yarrowia lipolytica Lipase Biosynthesis during Batch Cultures with Waste Fish Oil as a Carbon Source
Fermentation 2021, 7(2), 88; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020088 - 01 Jun 2021
Viewed by 827
Abstract
Yarrowia lipolytica is one of the most studied non-conventional forms of yeast, exhibiting a high secretory capacity and producing many industrially important and valuable metabolites. The yeast conceals a great biotechnological potential to synthesize organic acids, sweeteners, microbial oil, or fragrances. The vast [...] Read more.
Yarrowia lipolytica is one of the most studied non-conventional forms of yeast, exhibiting a high secretory capacity and producing many industrially important and valuable metabolites. The yeast conceals a great biotechnological potential to synthesize organic acids, sweeteners, microbial oil, or fragrances. The vast majority of bioprocesses are carried out in bioreactors, where suitable culture conditions are provided. In the current study, the effect of agitation speed (200–600 rpm) and air flow rate (0.0375–2.0 dm3/(dm3 × min)) on the biomass yield and lipase activity of Y. lipolytica KKP 379 is analyzed in a growth medium containing waste fish oil. The increase of aeration intensity limited the period of oxygen deficit in the medium. Simultaneously, an increase in lipolytic activity was observed from 2.09 U/cm3 to 14.21 U/cm3; however, an excessive agitation speed likely caused oxidative or shear stresses, and a reduction in lipolytic activity was observed. Moreover, it is confirmed that the synthesis of lipases is related to oxygen consumption, pH, and the yeast growth phase, and appropriate process selection may provide two advantages, namely, the maximum use of the waste carbon source and the production of lipolytic enzymes that are valuable in many industries. Full article
(This article belongs to the Special Issue Food Wastes: Feedstock for Value-Added Products 3.0)
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Review
Genetic, Physiological, and Industrial Aspects of the Fructophilic Non-Saccharomyces Yeast Species, Starmerella bacillaris
Fermentation 2021, 7(2), 87; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020087 - 01 Jun 2021
Cited by 1 | Viewed by 780
Abstract
Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast species, frequently found in enological ecosystems. Peculiar aspects of the genetics and metabolism of this yeast species, as well as potential industrial applications of isolated indigenous S. bacillaris strains worldwide, have recently [...] Read more.
Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast species, frequently found in enological ecosystems. Peculiar aspects of the genetics and metabolism of this yeast species, as well as potential industrial applications of isolated indigenous S. bacillaris strains worldwide, have recently been explored. In this review, we summarize relevant observations from studies conducted on standard laboratory and indigenous isolated S. bacillaris strains. Full article
(This article belongs to the Special Issue Enological Repercussions of Non-Saccharomyces Species 3.0)
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Article
Optimization of Yeast, Sugar and Nutrient Concentrations for High Ethanol Production Rate Using Industrial Sugar Beet Molasses and Response Surface Methodology
Fermentation 2021, 7(2), 86; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020086 - 31 May 2021
Cited by 1 | Viewed by 1143
Abstract
Among the various agro-industrial by-products, sugar beet molasses produced by sugar refineries appear as a potential feedstock for ethanol production through yeast fermentation. A response surface methodology (RSM) was developed to better understand the effect of three process parameters (concentration of nutrient, yeast [...] Read more.
Among the various agro-industrial by-products, sugar beet molasses produced by sugar refineries appear as a potential feedstock for ethanol production through yeast fermentation. A response surface methodology (RSM) was developed to better understand the effect of three process parameters (concentration of nutrient, yeast and initial sugar) on the ethanol productivity using diluted sugar beet molasses and Saccharomyces cerevisiae yeast. The first set of experiments performed at lab-scale indicated that the addition of 4 g/L of nutrient combined with a minimum of 0.2 g/L of yeast as well as a sugar concentration lower than 225 g/L was required to achieve high ethanol productivities (>15 g/L/d). The optimization allowed to considerably reduce the amount of yeast initially introduced in the fermentation substrate while still maximizing both ethanol productivity and yield process responses. Finally, scale-up assays were carried out in 7.5 and 100 L bioreactors using the optimal conditions: 150 g/L of initial sugar concentration, 0.27 g/L of yeast and 4 g/L of nutrient. Within 48 h of incubation, up to 65 g/L of ethanol were produced for both scales, corresponding to an average ethanol yield and sugar utilization rate of 82% and 85%, respectively. The results obtained in this study highlight the use of sugar beet molasses as a low-cost food residue for the sustainable production of bioethanol. Full article
(This article belongs to the Special Issue Food Waste Valorization)
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Article
Control of N-Propanol Production in Simulated Liquid State Fermentation of Chinese Baijiu by Response Surface Methodology
Fermentation 2021, 7(2), 85; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020085 - 31 May 2021
Viewed by 749
Abstract
N-propanol is a vital flavor compound of Chinese baijiu, and the proper n-propanol contents contribute to the rich flavor of Chinese baijiu. However, the excessive content of n-propanol in liquor will reduce the drinking comfort. Based on the Box–Behnken design principle, the response [...] Read more.
N-propanol is a vital flavor compound of Chinese baijiu, and the proper n-propanol contents contribute to the rich flavor of Chinese baijiu. However, the excessive content of n-propanol in liquor will reduce the drinking comfort. Based on the Box–Behnken design principle, the response surface test was used to optimize the factors affecting the production of n-propanol in a simulated liquid state fermentation of Chinese baijiu, and the best combination of factors to reduce n-propanol content was determined. Results showed that the content ratio of additional glucose to threonine and temperature had a significant effect on the production of n-propanol (p = 0.0009 < 0.01 and p = 0.0389 < 0.05, respectively). The best combination of fermentation parameters obtained was: the ratio of additional glucose to threonine content was 6:4, the temperature was 32 °C, and the initial pH was 4.40. Under these conditions, the production of n-propanol was 53.84 ± 0.12 mg/L, which was close to the theoretical value. Thus, the fermentation parameter model obtained through response surface optimization is reliable and can provide technical guidance for regulating the production of n-propanol and realizing high-quality baijiu brewing. Full article
(This article belongs to the Special Issue Advances in Beverages, Food, Yeast and Brewing Research)
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Article
Residual Brewing Yeast as Substrate for Co-Production of Cell Biomass and Biofilm Using Candida maltosa SM4
Fermentation 2021, 7(2), 84; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020084 - 30 May 2021
Viewed by 1124
Abstract
Candida maltosa was cultivated in the liquid phase of residual brewing yeast, a major brewery residue, to produce biomass and biofilm. Using response surface methodology, the effect of two variables at two different levels was investigated. The independent variables were agitation speed (at [...] Read more.
Candida maltosa was cultivated in the liquid phase of residual brewing yeast, a major brewery residue, to produce biomass and biofilm. Using response surface methodology, the effect of two variables at two different levels was investigated. The independent variables were agitation speed (at 100 and 200 rpm), and aeration (at 1 and 3 L min−1). Aeration was identified to be important for the production of both biomass and biofilm, while agitation was the only factor significantly affecting biofilm production. The maximal production of biofilm (2.33 g L−1) was achieved for agitation of 200 rpm and aeration of 1 L min−1, while the maximum for biomass (16.97 g L−1) was reached for 100 rpm agitation and 3 L min−1 air flow. A logistic model applied to predict the growth of C. maltosa in the exponential phase and the biofilm production, showed a high degree of agreement between the prediction and the actual biomass measured experimentally. The produced biofilms were further characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). FTIR allowed the identification of methyl, carbonyl ester and sulfate groups, and revealed the presence of uronic acid moieties and glycosidic bonds. Water-retention ability up to relatively high temperatures was revealed by TGA, and that makes the produced biofilm suitable for production of hydrogels. SEM also gave indications on the hydrogel-forming potential of the biofilm. Full article
(This article belongs to the Special Issue Food Wastes: Feedstock for Value-Added Products 2.0)
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Article
Application of Pichia kudriavzevii NBRC1279 and NBRC1664 to Simultaneous Saccharification and Fermentation for Bioethanol Production
Fermentation 2021, 7(2), 83; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020083 - 27 May 2021
Cited by 1 | Viewed by 779
Abstract
Simultaneous saccharification and fermentation (SSF) is capable of performing enzymatic saccharification and fermentation for biofuel production in a single vessel. Thus, SSF has several advantages such as simplifying the manufacturing process, operating easily, and reducing energy input. Here, we describe the application of [...] Read more.
Simultaneous saccharification and fermentation (SSF) is capable of performing enzymatic saccharification and fermentation for biofuel production in a single vessel. Thus, SSF has several advantages such as simplifying the manufacturing process, operating easily, and reducing energy input. Here, we describe the application of Pichia kudriavzevii NBRC1279 and NBRC1664 to SSF for bioethanol production. When each strain was incubated for 144 h at 35 °C with Japanese cedar particles, the highest ethanol concentrations were reached 21.9 ± 0.50 g/L and 23.8 ± 3.9 g/L, respectively. In addition, 21.6 ± 0.29 g/L and 21.3 ± 0.21 g/L of bioethanol were produced from Japanese eucalyptus particles when each strain was incubated for 144 h at 30 °C. Although previous methods require pretreatment of the source material, our method does not require pretreatment, which is an advantage for industrial use. To elucidate the different characteristics of the strains, we performed genome sequencing and genome comparison. Based on the results of the eggNOG categories and the resulting Venn diagram, the functional abilities of both strains were similar. However, strain NBRC1279 showed five retrotransposon protein genes in the draft genome sequence, which indicated that the stress tolerance of both strains is slightly different. Full article
(This article belongs to the Special Issue Biofuel Fermentation from Renewable Biomass)
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Article
Techno-Economic Analysis of Integrating Soybean Biorefinery Products into Corn-Based Ethanol Fermentation Operations
Fermentation 2021, 7(2), 82; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020082 - 25 May 2021
Viewed by 1075
Abstract
With the development of agricultural biorefineries and bioprocessing operations, understanding the economic efficiencies and environmental impacts for these have gradually become popular for the deployment of these industrial processes. The corn-based ethanol and soybean oil refining industries have been examined extensively over the [...] Read more.
With the development of agricultural biorefineries and bioprocessing operations, understanding the economic efficiencies and environmental impacts for these have gradually become popular for the deployment of these industrial processes. The corn-based ethanol and soybean oil refining industries have been examined extensively over the years, especially details of processing technologies, including materials, reaction controls, equipment, and industrial applications. The study focused on examining the production efficiency changes and economic impacts of integrating products from the enzyme-assisted aqueous extraction processing (EAEP) of soybeans into corn-based ethanol fermentation processing. Using SuperPro Designer to simulate production of corn-based ethanol at either 40 million gallons per year (MGY) or 120 MGY, with either oil separation or no oil removal, we found that indeed integrating soy products into corn ethanol fermentation may be slightly more expensive in terms of production costs, but economic returns justify this integration due to substantially greater quantities of ethanol, distillers corn oil, and distillers dried grains with solubles being produced. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology)
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Article
Preparation of Oil Palm Empty Fruit Bunch Hydrolysate
Fermentation 2021, 7(2), 81; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020081 - 25 May 2021
Viewed by 510
Abstract
Malaysia is the second largest palm oil producer and exporter globally. When crude palm oil is produced in both plantations and oil processing mills, a large amount of oil palm empty fruit bunch (OPEFB) is simultaneously produced as a waste product. Here, we [...] Read more.
Malaysia is the second largest palm oil producer and exporter globally. When crude palm oil is produced in both plantations and oil processing mills, a large amount of oil palm empty fruit bunch (OPEFB) is simultaneously produced as a waste product. Here, we describe the preparation of hydrolysate from OPEFB. After OPEFB was hydrothermally treated at 180–200 °C, the resultant liquid phase was subjected to high-performance liquid chromatography analysis, while the solid phase was used for acidic and enzymatic hydrolysis. Hemicellulose yield from the acid-treated solid phase decreased from 153 mg/g-OPEFB to 27.5 mg/g-OPEFB by increasing the hydrothermal treatment temperature from 180 to 200 °C. Glucose yield from the enzyme-treated solid phase obtained after hydrothermal treatment at 200 °C was the highest (234 ± 1.90 mg/g-OPEFB, 61.7% production efficiency). In contrast, xylose, mannose, galactose, and arabinose yields in the hydrolysate prepared from the solid phase hydrothermally treated at 200 °C were the lowest. Thus, we concluded that the optimum temperature for hydrothermal pretreatment was 200 °C, which was caused by the low hemicellulose yield. Based on these results, we have established an effective method for preparing OPEFB hydrolysates with high glucose content. Full article
(This article belongs to the Special Issue Biodegradation in Fermentation)
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Article
Acetaldehyde Stimulation of the Growth of Zymomonas mobilis Subjected to Ethanol and Other Environmental Stresses: Effect of Other Metabolic Electron Acceptors and Evidence for a Mechanism
Fermentation 2021, 7(2), 80; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020080 - 21 May 2021
Viewed by 459
Abstract
Ethanol-stressed cultures of Z. mobilis showed greatly reduced lag times in growth when supplemented with small amounts of acetaldehyde. This effect could be mimicked by other metabolic electron acceptors, including propionaldehyde and oxygen, indicating a redox-based mechanism. Added propionaldehyde was rapidly and stoichiometrically [...] Read more.
Ethanol-stressed cultures of Z. mobilis showed greatly reduced lag times in growth when supplemented with small amounts of acetaldehyde. This effect could be mimicked by other metabolic electron acceptors, including propionaldehyde and oxygen, indicating a redox-based mechanism. Added propionaldehyde was rapidly and stoichiometrically converted to 1-propanol, suggesting that added acetaldehyde is also reduced during early growth. Acetaldehyde addition measurably accelerated glycolysis in nongrowing cells and also slightly stimulated cultures subjected to temperature change, osmotic shock and salt and acetate stress. Acetaldehyde’s stimulatory effect appears to be due to its ability to accelerate glycolysis via its effect on the cellular redox balance. Acetaldehyde reduction opposes the drain on NAD+ concentrations caused by oxidation of the added ethanol, accounting for the particularly strong effect on ethanol-stressed cells. This study provides evidence for our earlier proposed redox-based mechanism for acetaldehyde’s ability to reduce the lag phase of environmentally stressed cultures and suggests that the effect may have applications in industrial fermentations, especially those inhibited by ethanol and toxic compounds present in, for instance, lignocellulosic hydrolysates. Full article
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Article
Use of Kluyveromyces marxianus to Increase Free Monoterpenes and Aliphatic Esters in White Wines
Fermentation 2021, 7(2), 79; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020079 - 18 May 2021
Cited by 1 | Viewed by 669
Abstract
An increasing interest in novel wine productions is focused on non-Saccharomyces yeasts due to their potential in improving sensory profiles. Although Kluyveromyces marxianus has been originally isolated from grapes and its enzymatic activities are used in oenology, rarely it has been used [...] Read more.
An increasing interest in novel wine productions is focused on non-Saccharomyces yeasts due to their potential in improving sensory profiles. Although Kluyveromyces marxianus has been originally isolated from grapes and its enzymatic activities are used in oenology, rarely it has been used as co-starter. The K. marxianus Km L2009 strain has been characterized here and selected as a co-starter both at laboratory- and winery-scale fermentation. The Km L2009 strain showed growth of up to 40 (mg/L) of sulfites and 6% (v/v) of ethanol. Gas chromatographic analysis demonstrates that wines produced by mixed fermentation contain remarkably higher quantities of free monoterpenes and aliphatic esters than wines produced only by commercial strains of Saccharomyces cerevisiae. Differences in the volatile organic compound composition produced sensorially distinct wines. In light of these results, it is possible to state that even within the K. marxianus species it is possible to select strains capable of improving the aromatic quality of wines. Full article
(This article belongs to the Special Issue Non-Saccharomyces Yeasts as Aroma Enhancers in Fermented Products)
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Article
Influence of Nitrogen Sources on D-Lactic Acid Biosynthesis by Sporolactobacillus laevolacticus DSM 442 Strain
Fermentation 2021, 7(2), 78; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020078 - 14 May 2021
Viewed by 773
Abstract
The purpose of this study was to explore the possibility of replacing an expensive yeast extract contained in the fermentation medium for D-lactic acid (D-LA, R-lactic acid) biosynthesis with an alternative nitrogen source. The screening studies were conducted under stationary conditions and showed [...] Read more.
The purpose of this study was to explore the possibility of replacing an expensive yeast extract contained in the fermentation medium for D-lactic acid (D-LA, R-lactic acid) biosynthesis with an alternative nitrogen source. The screening studies were conducted under stationary conditions and showed that pea seed hydrolysate was the most beneficial substrate in the process of D-LA biosynthesis by the strain Sporolactobacillus laevolacticus DSM 442 among the used inorganic and organic nitrogen sources, waste materials, food and agricultural products. After 96 h, 75.5 g/L D-LA was obtained in batch cultures in a medium containing pea seed hydrolysate, with an average productivity of 0.79 g/L/h, yield of 75.5%, and optical purity of 99.4%. In batch cultures fed once, in a medium with an analogous composition, 122.6 g/L D-LA was obtained after 120 h, and the average yield, productivity and optical purity were 87.6%, 1.021 g/L/h, and 99.6%, respectively. Moreover, the amount of D-LA obtained in the fermentation medium enriched with the above-mentioned cheap agricultural product was similar to the amounts obtained in the medium containing yeast extract in both stationary and bioreactor cultures. Our research shows that hydrolyzed pea seeds, which belong to the legume family, may be a promising nitrogen source for the production of D-LA on an industrial scale. Full article
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Editorial
Biomass Conversion: Fermentation Chemicals and Fuels
Fermentation 2021, 7(2), 77; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020077 - 13 May 2021
Viewed by 551
Abstract
Rendezvous with Rama [...] Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
Review
Potential Role of Sequential Solid-State and Submerged-Liquid Fermentations in a Circular Bioeconomy
Fermentation 2021, 7(2), 76; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020076 - 11 May 2021
Cited by 5 | Viewed by 676
Abstract
An efficient processing of organic solid residues will be pivotal in the development of the circular bioeconomy. Due to their composition, such residues comprise a great biochemical conversion potential through fermentations. Generally, the carbohydrates and proteins present in the organic wastes cannot be [...] Read more.
An efficient processing of organic solid residues will be pivotal in the development of the circular bioeconomy. Due to their composition, such residues comprise a great biochemical conversion potential through fermentations. Generally, the carbohydrates and proteins present in the organic wastes cannot be directly metabolized by microorganisms. Thus, before fermentation, enzymes are used in a hydrolysis step to release digestible sugars and nitrogen. Although enzymes can be efficiently produced from organic solid residues in solid-state fermentations (SsF), challenges in the development and scale-up of SsF technologies, especially bioreactors, have hindered a wider application of such systems. Therefore, most of the commercial enzymes are produced in submerged-liquid fermentations (SmF) from expensive simple sugars. Instead of independently evaluating SsF and SmF, the review covers the option of combining them in a sequential process in which, enzymes are firstly produced in SsF and then used for hydrolysis, yielding a suitable medium for SmF. The article reviews experimental work that has demonstrated the feasibility of the process and underlines the benefits that such combination has. Finally, a discussion is included which highlights that, unlike typically perceived, SsF should not be considered a counterpart of SmF but, in contrast, the main advantages of each type of fermentation are accentuated in a synergistic sequential SsF-SmF. Full article
(This article belongs to the Special Issue Solid State Fermentations)
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Article
Utilization of Whey for Red Pigment Production by Monascus purpureus in Submerged Fermentation
Fermentation 2021, 7(2), 75; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020075 - 10 May 2021
Cited by 2 | Viewed by 815
Abstract
Various biotechnological approaches have been employed to convert food waste into value-added bioproducts through fermentation processes. Whey, a major waste generated by dairy industries, is considered an important environmental pollutant due to its massive production and high organic content. The purpose of this [...] Read more.
Various biotechnological approaches have been employed to convert food waste into value-added bioproducts through fermentation processes. Whey, a major waste generated by dairy industries, is considered an important environmental pollutant due to its massive production and high organic content. The purpose of this study is to investigate the effect of different fermentation parameters in simultaneous hydrolysis and fermentation (SHF) of whey for pigment production with Monascus purpureus. The submerged culture fermentation parameters optimized were type and pretreatment of whey, pH, inoculation ratio, substrate concentration and monosodium glutamate (MSG) concentration. Demineralized (DM), deproteinized (DP), and raw whey (W) powders were used as a substrate for pigment production by simultaneous hydrolysis and fermentation (SHF). The maximum red pigment production was obtained as 38.4 UA510 nm (absorbance units) at the optimized condition of SHF. Optimal conditions of SHF were 2% (v/v) inoculation ratio, 75 g/L of lactose as carbon source, 25 g/L of MSG as nitrogen source, and fermentation medium pH of 7.0. The specific growth rate of M. purpureus on whey and the maximum pigment production yield values were 0.023 h−1 and 4.55 UAd−1, respectively. This study is the first in the literature to show that DM whey is a sustainable substrate in the fermentation process of the M. purpureus red pigment. Full article
(This article belongs to the Special Issue Food Waste Valorization)
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Article
Screening and Evaluation of Purine-Nucleoside-Degrading Lactic Acid Bacteria Isolated from Winemaking Byproducts In Vitro and Their Uric Acid-Lowering Effects In Vivo
Fermentation 2021, 7(2), 74; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020074 - 10 May 2021
Viewed by 628
Abstract
In Taiwan, adult hyperuricemia affects as many as 1 in 4 males and 1 in 6 females, who are predominantly young adults aged 19–45. In this study, lactic acid bacteria (LAB) with acid tolerance, bile salt tolerance and high affinity to intestinal cells [...] Read more.
In Taiwan, adult hyperuricemia affects as many as 1 in 4 males and 1 in 6 females, who are predominantly young adults aged 19–45. In this study, lactic acid bacteria (LAB) with acid tolerance, bile salt tolerance and high affinity to intestinal cells were extracted from the side products of alcohol fermentation (distillers’ grains). These bacteria were evaluated for their ability to lower uric acid levels. Qualitative identification and quantitative analysis were performed using high-performance liquid chromatography (HPLC) on the purine-degrading enzymes to select purine-decomposing LAB for animal testing. When the final concentration of purine compounds reached 0.1% and 1%, seven strains of LAB showed potential in degrading purine compounds. HPLC was used to analyze their purine-degrading abilities, and the three best performing LAB strains, (107) 8–16, (107) tau 1–3, and (107) 6–10 were screened for further animal testing with Wistar rats. By the third week, the results showed that strain (107) 6–10 could prevent formation and reduce the levels of blood urea nitrogen (BUN) in yeast extract/potassium oxonate-induced hyperuricemia. The multi-strain lactic acid bacteria (MLAB) performed best for uric acid reduction in the serum and down regulated BUN. Yeast extract/potassium oxonate-induced hyperuricemia had no impact on serum creatinine, while LAB did not affect the creatinine concentration. In summary, MLAB not only protects kidney function but is also effective in regulating uric acid concentration in the body. Hence, MLAB can be used as a functional food supplement that prevents or aids the treatment of hyperuricemia in a rodent model. Full article
(This article belongs to the Special Issue Fermented Foods and Microbes Related to Health)
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Article
LC-ESI-QTOF-MS/MS Characterisation of Phenolics in Herbal Tea Infusion and Their Antioxidant Potential
Fermentation 2021, 7(2), 73; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020073 - 10 May 2021
Cited by 3 | Viewed by 755
Abstract
Ginger (Zingiber officinale R.), lemon (Citrus limon L.) and mint (Mentha sp.) are commonly consumed medicinal plants that have been of interest due to their health benefits and purported antioxidant capacities. This study was conducted on the premise that [...] Read more.
Ginger (Zingiber officinale R.), lemon (Citrus limon L.) and mint (Mentha sp.) are commonly consumed medicinal plants that have been of interest due to their health benefits and purported antioxidant capacities. This study was conducted on the premise that no previous study has been performed to elucidate the antioxidant and phenolic profile of the ginger, lemon and mint herbal tea infusion (GLMT). The aim of the study was to investigate and characterise the phenolic contents of ginger, lemon, mint and GLMT, as well as determine their antioxidant potential. Mint recorded the highest total phenolic content, TPC (14.35 ± 0.19 mg gallic acid equivalent/g) and 2,2′-azino-bis(3-e-thylbenzothiazoline-6-sulfonic acid), ABTS (24.25 ± 2.18 mg ascorbic acid equivalent/g) antioxidant activity. GLMT recorded the highest antioxidant activity in the reducing power assay, RPA (1.01 ± 0.04 mg ascorbic acid equivalent/g) and hydroxyl radical scavenging assay, OH-RSA (0.77 ± 0.08 mg ascorbic acid equivalent/g). Correlation analysis showed that phenolic content positively correlated with the antioxidant activity. Venn diagram analysis revealed that mint contained a high proportion of exclusive phenolic compounds. Liquid chromatography coupled with electrospray ionisation and quadrupole time of flight tandem mass spectrometry (LC-ESI-QTOF-MS/MS) characterised a total of 73 phenolic compounds, out of which 11, 31 and 49 were found in ginger, lemon and mint respectively. These characterised phenolic compounds include phenolic acids (24), flavonoids (35), other phenolic compounds (9), lignans (4) and stilbene (1). High-performance liquid chromatography photometric diode array (HPLC-PDA) quantification showed that GLMT does contain a relatively high concentration of phenolic compounds. This study presented the phenolic profile and antioxidant potential of GLMT and its ingredients, which may increase the confidence in developing GLMT into functional food products or nutraceuticals. Full article
(This article belongs to the Special Issue Implementation of Digital Technologies on Beverage Fermentation)
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Article
A Statistical Workflow to Evaluate the Modulation of Wine Metabolome and Its Contribution to the Sensory Attributes
Fermentation 2021, 7(2), 72; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020072 - 05 May 2021
Cited by 1 | Viewed by 893
Abstract
A data-processing and statistical analysis workflow was proposed to evaluate the metabolic changes and its contribution to the sensory characteristics of different wines. This workflow was applied to rosé wines from different fermentation strategies. The metabolome was acquired by means of two high-throughput [...] Read more.
A data-processing and statistical analysis workflow was proposed to evaluate the metabolic changes and its contribution to the sensory characteristics of different wines. This workflow was applied to rosé wines from different fermentation strategies. The metabolome was acquired by means of two high-throughput techniques: gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) for volatile and non-volatile metabolites, respectively, in an untargeted approach, while the sensory evaluation of the wines was performed by a trained panel. Wine volatile and non-volatile metabolites modulation was independently evaluated by means of partial least squares discriminant analysis (PLS-DA), obtaining potential markers of the fermentation strategies. Then, the complete metabolome was integrated by means of sparse generalised canonical correlation analysis discriminant analysis (sGCC-DA). This integrative approach revealed a high link between the volatile and non-volatile data, and additional potential metabolite markers of the fermentation strategies were found. Subsequently, the evaluation of the contribution of metabolome to the sensory characteristics of wines was carried out. First, the all-relevant metabolites affected by the different fermentation processes were selected using PLS-DA and random forest (RF). Each set of volatile and non-volatile metabolites selected was then related to the sensory attributes of the wines by means of partial least squares regression (PLSR). Finally, the relationships among the three datasets were complementary evaluated using regularised generalised canonical correlation analysis (RGCCA), revealing new correlations among metabolites and sensory data. Full article
(This article belongs to the Special Issue Advances in Wine Fermentation)
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Article
Modeling of Hydrogen Production by Applying Biomass Gasification: Artificial Neural Network Modeling Approach
Fermentation 2021, 7(2), 71; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020071 - 01 May 2021
Cited by 1 | Viewed by 882
Abstract
In order to accurately anticipate the proficiency of downdraft biomass gasification linked with a water–gas shift unit to produce biohydrogen, a model based on an artificial neural network (ANN) approach is established to estimate the specific mass flow rate of the biohydrogen output [...] Read more.
In order to accurately anticipate the proficiency of downdraft biomass gasification linked with a water–gas shift unit to produce biohydrogen, a model based on an artificial neural network (ANN) approach is established to estimate the specific mass flow rate of the biohydrogen output of the plant based on different types of biomasses and diverse operating parameters. The factors considered as inputs to the models are elemental and proximate analysis compositions as well as the operating parameters. The model structure includes one layer for input, a hidden layer and output layer. One thousand eight hundred samples derived from the simulation of 50 various feedstocks in different operating situations were utilized to train the developed ANN model. The established ANN in the case of product biohydrogen presents satisfactory agreement with input data: absolute fraction of variance (R2) is more than 0.999 and root mean square error (RMSE) is lower than 0.25. In addition, the relative impact of biomass properties and operating parameters on output are studied. At the end, to have a comprehensive evaluation, variations of the inputs regarding hydrogen-content are compared and evaluated together. The results show that almost all of the inputs show a significant impact on the smhydrogen output. Significantly, gasifier temperature, SBR, moisture content and hydrogen have the highest impacts on the smhydrogen with contributions of 19.96, 17.18, 15.3 and 10.48%, respectively. In addition, other variables in feed properties, like C, O, S and N present a range of 1.28–8.6% and proximate components like VM, FC and A present a range of 3.14–7.67% of impact on smhydrogen. Full article
(This article belongs to the Special Issue Recent Trends in Biogenic Gas, Waste and Wastewater Fermentation)
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Article
Valorization of Rice Husk for the Production of Porous Biochar Materials
Fermentation 2021, 7(2), 70; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020070 - 30 Apr 2021
Cited by 2 | Viewed by 696
Abstract
Rice husk (RH) is one of the most important crop residues around the world, making its valorization an urgent and important topic in recent years. This work focused on the production of RH-based biochars at different pyrolysis temperatures from 400 to 900 °C [...] Read more.
Rice husk (RH) is one of the most important crop residues around the world, making its valorization an urgent and important topic in recent years. This work focused on the production of RH-based biochars at different pyrolysis temperatures from 400 to 900 °C and holding times from 0 to 90 min. Furthermore, the variations in the yields and pore properties of the resulting biochars were related to these process conditions. The results showed that the pore properties (i.e., BET surface area and porosity) of the resulting RH-based biochar were positively correlated with the ranges of pyrolysis temperature and holding time studied. The maximal pore properties with a BET surface area of around 280 m2/g and porosity of 0.316 can be obtained from the conditions at 900 °C for a holding time of 90 min. According to the data on the nitrogen (N2) adsorption–desorption isotherms and pore size distributions, both microporous and mesoporous structures exist in the resulting biochar. In addition, the EDS and FTIR analyses also supported the slight hydrophilicity on the surface of the RH-based biochar due to the oxygen/silica-containing functional groups. Based on the findings of this work, the RH-based biochar could be used as a material in environmental applications for water conservation, wastewater treatment and soil amendment. Full article
(This article belongs to the Special Issue Food Waste Valorization)
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Editorial
Yeast Biotechnology 4.0
Fermentation 2021, 7(2), 69; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7020069 - 30 Apr 2021
Cited by 1 | Viewed by 736
Abstract
This Special Issue is a continuation of the first, second, and third “Yeast Biotechnology” Special Issue series of the journal Fermentation (MDPI) [...] Full article
(This article belongs to the Special Issue Yeast Biotechnology 4.0)
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