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Fermentation
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Bioconversion of Lignocellulosic Materials to Value-Added Products
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Bioconversion of Lignocellulosic Materials to Value-Added Products

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Industrial Fermentation".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 28676

Special Issue Editors

Prof. Dr. Alexander Rapoport

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Guest Editor
Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
Interests: yeast cytology; yeast physiology; yeast biotechnology; yeast response to stress treatments; intracellular protective reactions; dehydration-rehydration of microorganisms; anhydrobiosis; bioconversion of lignocellulose
Special Issues, Collections and Topics in MDPI journals
Dr. John E. Hallsworth

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Guest Editor
Institute for Global Food Security, School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, Northern Ireland BT9 5DL, UK
Interests: aspergillus; bioethanol; biophysical constraints; bioprospecting; cellular stress responses; chaotropicity; culture-based techniques; environmental sampling; HPLC; osmotic stress; Pleurotus; product toxicity; Pseudomonas putida; Saccharomyces cerevisiae; saprotrophic metabolism; water activity
Dr. Justyna Ruchala

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Guest Editor
College of Natural Sciences, University of Rzeszow, Rzeszow, Poland
Interests: non-conventional yeasts; genetic engineering; cell biology; yeast biotechnology; production of biotechnologically useful chemical compounds
Dr. Tiffany D. Dallas

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Guest Editor
Institute for Global Food Security, School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, Northern Ireland BT9 5DL, UK
Interests: analytical techniques; bioprospecting; bioprocess optimization; cell biology; genetic engineering; industrial fermentation; Penicillium; soil microbiology; space biotechnologies

Special Issue Information

Dear colleagues

Many kinds of natural waste material have the potential to be converted into high-value products, including biofuels, pharmaceuticals, vitamins, cosmetics, and fine chemicals. For example, lignocellulosic materials, including various cellulose-containing energy crops, forestry waste, agriculture residues, and wastes from biorefineries, pulp mills and other industries. What is more, lignocellulose is a renewable resource that is inexpensive and readily available in most parts of the world. Its constituents—hemicellulose, cellulose, and lignin—each have value for microbial bioconversions. Lignocellulosic biomass can contribute to global energy supply without competing with the need for agricultural food production.  

This Special Issue invites research opinion and review articles relating to the conversion of lignocellulose to value-added products, including pre-treatments. Topics include (but are not restricted to):

- obtaining of different products from lignocellulose

- bioprospecting for novel microbes

- use of microbial consortia

- toxicity of breakdown products

- bioinformatic approaches

- metabolic engineering

- manipulation of phenotypic plasticity

- enzyme kinetics

- anaerobic fermentation

- substrate formulation and pre-treatment

- combining biological and chemical approaches

- cell-free systems

- renewable energy

- bioprocess optimisation

Dr. John E. Hallsworth
Prof. Dr. Alexander Rapoport
Dr. Justyna Ruchala
Dr. Tiffany D. Dallas
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fermentation is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bioprocessing
  • cellulose
  • fermentation
  • hemicellulose
  • lignin
  • lignocellulose
  • metabolic engineering
  • microbial factories
  • value-added products

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Published Papers (11 papers)

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Research

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16 pages, 671 KiB  
Article
Identification, Quantification and Kinetic Study of Carotenoids and Lipids in Rhodotorula toruloides CBS 14 Cultivated on Wheat Straw Hydrolysate
by Yashaswini Nagavara Nagaraj, Viktoriia Burkina, Laura Okmane, Johanna Blomqvist, Alexander Rapoport, Mats Sandgren, Jana Pickova, Sabine Sampels and Volkmar Passoth
Fermentation 2022, 8(7), 300; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation8070300 - 25 Jun 2022
Cited by 16 | Viewed by 2229
Abstract
Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and carotenoid kinetics [...] Read more.
Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and carotenoid kinetics during cultivation were determined. The carotenoids β-carotene, γ-carotene, torularhodin, and torulene were identified; β-carotene was the major carotenoid, reaching a maximum of 1.48 mg/100 g dry weight. Recoveries of the carotenoids were between 66% and 76%, except torulene and torularhodin, which had lower recoveries due to saponification effects. Total carotenoid content in saponified and unsaponified yeast extract, respectively, determined by UHPLC or photometer, respectively, was 1.99 mg/100 g and 4.02 mg β-EQ/100 g dry weight. Growth kinetics showed a positive correlation between carotenoid content and lipid accumulation. β-carotene was the major carotenoid at all time points. At the end of the cultivation, triacylglycerols (TAGs) were the major lipid class, with 58.1% ± 3.32% of total lipids. There was also a high proportion of free fatty acids, reaching from 20.5% to 41.8% of total lipids. Oleic acid (C18:1) was the major fatty acid. The lipid yield at the end of the cultivation was 0.13 g/g of sugar consumed. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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11 pages, 2041 KiB  
Article
Improved Hydrogen Peroxide Stress Resistance of Zymomonas mobilis NADH Dehydrogenase (ndh) and Alcohol Dehydrogenase (adhB) Mutants
by Kristiana Kovtuna, Inese Strazdina, Mara Bikerniece, Nina Galinina, Reinis Rutkis, Jekaterina Martynova and Uldis Kalnenieks
Fermentation 2022, 8(6), 289; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation8060289 - 19 Jun 2022
Viewed by 1693
Abstract
Unintended shifts in stress resistance of microbial strains with engineered central metabolism may impact their growth and production performance under oxidative, lignocellulosic, solvent, and other stress conditions, and as such, must be taken into account in bioprocess design. In the present work, we [...] Read more.
Unintended shifts in stress resistance of microbial strains with engineered central metabolism may impact their growth and production performance under oxidative, lignocellulosic, solvent, and other stress conditions, and as such, must be taken into account in bioprocess design. In the present work, we studied oxidative stress resistance in mutant strains of the facultatively anaerobic, ethanologenic bacterium Zymomonas mobilis with modified respiratory (inactivated NADH dehydrogenase Ndh, by disruption of ndh) and ethanologenic (inactivated iron-containing alcohol dehydrogenase isoenzyme ADH II, by disruption of adhB) catabolism, using exogenously added H2O2 in the concentration range of 2–6 mM as the oxidative stressor. Both mutations improved H2O2 resistance and enhanced catalase activity by a factor of 2–5, while the overexpression of Ndh had an opposite effect. Strains with a catalase-negative background were unable to grow already at 1 mM hydrogen peroxide, and their H2O2 resistance did not depend on AdhB or Ndh expression levels. Hence, the improved resistance of the ndh and adhB mutants to H2O2 resulted from their elevated catalase activity. The interrelation between these mutations, the catabolic redox balance, catalase activity, and oxidative stress defense in Z. mobilis is discussed. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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10 pages, 988 KiB  
Article
Co-Overexpression of RIB1 and RIB6 Increases Riboflavin Production in the Yeast Candida famata
by Yana Petrovska, Oleksii Lyzak, Justyna Ruchala, Kostyantyn Dmytruk and Andriy Sibirny
Fermentation 2022, 8(4), 141; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation8040141 - 25 Mar 2022
Cited by 5 | Viewed by 2561
Abstract
Riboflavin or vitamin B2 is a water-soluble vitamin and a precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which play a key role as enzyme cofactors in energy metabolism. Candida famata yeast is a promising producer of riboflavin, as it belongs [...] Read more.
Riboflavin or vitamin B2 is a water-soluble vitamin and a precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which play a key role as enzyme cofactors in energy metabolism. Candida famata yeast is a promising producer of riboflavin, as it belongs to the group of so-called flavinogenic yeasts, capable of riboflavin oversynthesis under conditions of iron starvation. The role of the particular structural genes in the limitation of riboflavin oversynthesis is not known. To study the impact of overexpression of the structural genes of riboflavin synthesis on riboflavin production, a set of plasmids containing genes RIB1, RIB6, and RIB7 in different combinations was constructed. The transformants of the wild-type strain of C. famata, as well as riboflavin overproducer, were obtained, and the synthesis of riboflavin was studied. It was found that overexpression of RIB1 and RIB6 genes coding for enzymes GTP cyclohydrolase II and 3,4-dihydroxy-2-butanone-4-phosphate synthase, which catalase the initial steps of riboflavin synthesis, elevated riboflavin production by 13–28% relative to the parental riboflavin-overproducing strains. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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14 pages, 3412 KiB  
Article
Antimicrobial Activity of Zymomonas mobilis Is Related to Its Aerobic Catabolism and Acid Resistance
by Reinis Rutkis, Zane Ļaša, Marta Rubina, Rita Ščerbaka, Gints Kalniņš, Jānis Bogans and Uldis Kalnenieks
Fermentation 2022, 8(2), 77; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation8020077 - 12 Feb 2022
Cited by 1 | Viewed by 2753
Abstract
Zymomonas mobilis is an ethanologenic, facultatively anaerobic alpha-proteobacterium, known for its inhibitory effect on the growth of a wide variety of microorganisms. This property might be interesting for the design of novel antimicrobials, yet it has negative implications for biotechnology, as it hinders [...] Read more.
Zymomonas mobilis is an ethanologenic, facultatively anaerobic alpha-proteobacterium, known for its inhibitory effect on the growth of a wide variety of microorganisms. This property might be interesting for the design of novel antimicrobials, yet it has negative implications for biotechnology, as it hinders the use of Z. mobilis as a producer microorganism in cocultivation. So far, the chemical nature of its inhibitory compound(s) has not been established. In the present study, we demonstrate that the putative inhibitor is a low-molecular-weight (below 3 kDa), thermostable compound, resistant to protease treatment, which is synthesized under aerobic conditions in Z. mobilis strains via the active respiratory chain. It is also synthesized by aerated nongrowing, glucose-consuming cells in the presence of chloramphenicol, thus ruling out its bacteriocin-like peptide nature. The inhibitory activity is pH-dependent and strongly correlated with the accumulation of propionate and acetate in the culture medium. Although, in Z. mobilis, the synthesis pathways of these acids still need to be identified, the acid production depends on respiration, and is much less pronounced in the non-respiring mutant strain, which shows low inhibitory activity. We conclude that propionate and acetate play a central role in the antimicrobial effects of Z. mobilis, which itself is known to bear high resistance to organic acids. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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14 pages, 1261 KiB  
Article
Triacyl Glycerols from Yeast-Catalyzed Batch and Fed-Batch Bioconversion of Hydrolyzed Lignocellulose from Cardoon Stalks
by Domenico Aiello, Ciro Sannino, Tommaso Giannoni, Giacomo Fabbrizi, Mattia Gelosia, Andrea Nicolini, Benedetta Turchetti, Franco Cotana and Pietro Buzzini
Fermentation 2021, 7(4), 315; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7040315 - 16 Dec 2021
Cited by 4 | Viewed by 2144
Abstract
The lipogenic ability of the yeast Solicoccozyma terricola DBVPG 5870 grown on hydrolyzed lignocellulose obtained from cardoon stalks was evaluated. Data on cell biomass, lipid production, and fatty acid profiles of triacylglycerols obtained in batch and fed-batch experiments were carried out at the [...] Read more.
The lipogenic ability of the yeast Solicoccozyma terricola DBVPG 5870 grown on hydrolyzed lignocellulose obtained from cardoon stalks was evaluated. Data on cell biomass, lipid production, and fatty acid profiles of triacylglycerols obtained in batch and fed-batch experiments were carried out at the laboratory scale in a 5L fermenter, and at two different temperatures (20 and 25 °C) were reported. The higher production of total intracellular lipids (13.81 g/L) was found in the fed-batch experiments carried out at 20 °C. S. terricola exhibited the ability to produce high amounts of triacylglycerol (TAGs) with a characteristic fatty acids profile close to that of palm oil. The TAGs obtained from S. terricola grown on pre-treated lignocellulose could be proposed as a supplementary source of oleochemicals. Indeed, due to the rising prices of fossil fuels and because of the environmental-related issues linked to their employment, the use of TAGs produced by S. terricola grown on lignocellulose could represent a promising option as a supplementary oleochemical, especially for biodiesel production. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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14 pages, 286 KiB  
Article
The Effects of Oil Palm Fronds Silage Supplemented with Urea-Calcium Hydroxide on Rumen Fermentation and Nutrient Digestibility of Thai Native-Anglo Nubian Goats
by Pin Chanjula, Chanon Suntara and Anusorn Cherdthong
Fermentation 2021, 7(4), 218; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7040218 - 08 Oct 2021
Cited by 4 | Viewed by 2269
Abstract
This study aimed to examine the combined effects of urea and calcium hydroxide ensiled oil palm fronds on rumen fermentation and digestibility of Thai native-Anglo Nubian goats. A 4 × 4 Latin square design was used to randomly assign four male crossbred goats [...] Read more.
This study aimed to examine the combined effects of urea and calcium hydroxide ensiled oil palm fronds on rumen fermentation and digestibility of Thai native-Anglo Nubian goats. A 4 × 4 Latin square design was used to randomly assign four male crossbred goats (Thai native × Anglo Nubian). The dietary treatments were as follows: ensiled oil palm frond with no additives (EOPF as the control), urea 5% (50 g/kg fresh matter) (E-UOPF 5%), calcium hydroxide (Ca(OH)2) 5% (50 g/kg fresh matter) (E-CaOPF 5%), and combination of urea 2.5% (25 g/kg fresh matter) with Ca(OH)2 (25 g/kg fresh matter) (E-UCOPF 2.5%). The oil palm frond ensiled with different additives did not change the DM intake (p > 0.05). The total TMR intakes range from 69.39 to 77.09 g/kg BW0.75. The goats fed with E-UOPF 5.0% consumed significantly more CP than the other groups (p < 0.05). The E-UCOPF increased ME intake by 4.8%, compared with the control treatment (p < 0.05). E-UOPF 5% and E-UCOPF 2.5% significantly increased the CP digestibility by 19.7% and 17.1%, respectively (p < 0.05). Furthermore, E-CaOPF 5.0% and E-UCOPF 2.5% improved the NDF digestibility by about 10.9% and 9.90%, respectively (p < 0.05). The urea-containing oil palm frond (E-UOPF 5.0% and E-UCOPF 2.5%) had higher blood urea nitrogen (BUN) than the other groups (p < 0.05). The TVFA of goats fed E-UCOPF 2.5% was approximately 15.8% higher than that of goats provide EOPF (p < 0.05). The mean concentration of C3 increased by 7.90% and 11.61%, respectively, when E-CaOPF 5.0% and E-UCOPF 2.5% were provided instead of EOPF (p < 0.05). The total N intake and absorbed were highest (p < 0.05) when goats offered E-UOPF 5.0% (p < 0.05). The goats fed oil palm frond without additives had the lowest percentage of N-absorption/N intake (p < 0.05). This study clearly shows that the most suitable treatment is E-UCOPF 2.5%, which enhances DMD, nutrient digestibility, TVFAs, and nitrogen balance and has no negative effects on rumen microbes. This indicates that E-UCOPF 2.5% may be utilized as an alternate roughage source in TMR diets, accounting for at least 40% of the OPF. However, several factors still require consideration for urea-Ca(OH)2 treatments to be successful, including other concentrations of urea, moisture content, duration of pre-treatment, and the metabolizable protein system. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
10 pages, 1157 KiB  
Article
Rhodaneses Enzyme Addition Could Reduce Cyanide Concentration and Enhance Fiber Digestibility via In Vitro Fermentation Study
by Chanadol Supapong and Anusorn Cherdthong
Fermentation 2021, 7(4), 207; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7040207 - 25 Sep 2021
Cited by 6 | Viewed by 1991
Abstract
The use of cyanide-containing feed (HCN) is restricted because it causes prussic acid poisoning in animals. The objective of this study was to see how adding rhodanese enzyme to an HCN-containing diet affected gas dynamics, in vitro ruminal fermentation, HCN concentration reduction, and [...] Read more.
The use of cyanide-containing feed (HCN) is restricted because it causes prussic acid poisoning in animals. The objective of this study was to see how adding rhodanese enzyme to an HCN-containing diet affected gas dynamics, in vitro ruminal fermentation, HCN concentration reduction, and nutrient digestibility. A 3 × 4 factorial arrangement in a completely randomized design was used for the experiment. Factor A was the three levels of potassium cyanide (KCN) at 300, 450, and 600 ppm. Factor B was the four doses of rhodanese enzyme at 0, 0.65, 1, and 1.35 mg/104 ppm KCN, respectively. At 96 h of incubation, gas production from an insoluble fraction (b), potential extent (omit gas) (a + b), and cumulative gas were similar between KCN additions of 300 to 450 ppm (p > 0.05), whereas increasing KCN to 600 ppm significantly decreased those kinetics of gas (p < 0.05). Supplementation of rhodanese enzymes at 1.0 to 1.35 mg/104 ppm KCN enhanced cumulative gas when compared to the control group (p < 0.05). Increasing the dose of rhodanese up to 1.0 mg/104 ppm KCN significantly increased the rate of ruminal HCN degradation efficiency (DE) by 70% (p < 0.05). However, no further between the two factors was detected on ruminal fermentation and in vitro digestibility (p > 0.05). The concentration of ammonia-nitrogen (NH3-N) increased with increasing doses of KCN (p < 0.05), but remained unchanged with varying levels of rhodanese enzymes (p > 0.05). The in vitro dry matter digestibility (IVDMD) was suppressed when increasing doses of KCH were administered at 600 ppm, whereas supplementation of rhodanese enzymes at 1.0–1.35 mg/104 ppm KCN enhanced IVDMD (p < 0.05). Increasing doses of KCN affected reduced total volatile fatty acids (TVFA) concentration, which was lowest when 600 ppm was added (p < 0.05). Nevertheless, the concentration of TVFAs increased when rhodanese enzymes were included by 1.0–1.35 mg/104 ppm KCN (p < 0.05). Based on this study, it could be concluded that supplementation of rhodaneses enzyme at 1.0–1.35 mg/104 ppm KCN could enhance cumulative gas, digestibility, and TVAF, as well as lowering ruminal HCN concentration. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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12 pages, 2206 KiB  
Article
Effect of Pretreated Colza Straw on the Growth and Extracellular Ligninolytic Enzymes Production by Lentinula edodes and Ganoderma lucidum
by Galina Makarenkova, Valda Balode, Dzintra Zala, Elina Azena, Alexander Rapoport and Indrikis Muiznieks
Fermentation 2021, 7(3), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7030157 - 17 Aug 2021
Cited by 2 | Viewed by 2290
Abstract
Lentinula edodes 3565 and Ganoderma lucidum 9621 were compared for their ability to produce lignocellulolytic enzymes in submerged (SM) and surface liquid (SL) fermentation of hydrolysed colza straw lignin waste that remained after the production of furfural and bioethanol (CS lignin). Application of [...] Read more.
Lentinula edodes 3565 and Ganoderma lucidum 9621 were compared for their ability to produce lignocellulolytic enzymes in submerged (SM) and surface liquid (SL) fermentation of hydrolysed colza straw lignin waste that remained after the production of furfural and bioethanol (CS lignin). Application of cultivated mushrooms to dispose of pretreated colza straw agricultural waste is an approach to decrease the quantity of residual lignin while simultaneously obtaining active substances, e.g., the ligninolytic enzyme complex from mycelium. The effect of adding CS lignin to culture media on the yield of L. edodes and G. lucidum mycelium and extracellular laccase activity was studied. It was revealed that the mycelial growth of G. lucidum on solid media was significantly improved by adding CS lignin. Laccase activity during SL cultivation of L. edodes on medium with CS lignin gradually increased over the experiment starting on day 21 and peaked at 520 U/mL on day 28. G. lucidum expressed the maximum laccase activity, 540 U/mL, during the first 14 days of mycelium SM cultivation. Extracellular laccase activity was enhanced about 35- to 40-fold at cultivation of L. edodes and about 10- to 15-fold in the case of G. lucidum by supplementing liquid culture media with CS lignin. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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14 pages, 1561 KiB  
Article
Bored Coffee Beans for Production of Hyaluronic Acid by Streptococcus zooepidemicus
by David Antonio Flores-Méndez, José Roberto Ramos-Ibarra, Guillermo Toriz, Enrique Arriola-Guevara, Guadalupe Guatemala-Morales and Rosa Isela Corona-González
Fermentation 2021, 7(3), 121; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7030121 - 17 Jul 2021
Cited by 5 | Viewed by 2419
Abstract
Bored coffee beans (BCBs) are the residues left from the pest Hypothenemus hampei that attacks coffee crops, resulting in enormous economic losses. The bioconversion of monosaccharides from BCBs into hyaluronic acid (HA) is appealing both for using the residues and given the high [...] Read more.
Bored coffee beans (BCBs) are the residues left from the pest Hypothenemus hampei that attacks coffee crops, resulting in enormous economic losses. The bioconversion of monosaccharides from BCBs into hyaluronic acid (HA) is appealing both for using the residues and given the high commercial value of HA. This study dealt with the production of HA using Streptococcus zooepidemicus by employing either acid (AcH) or enzymatic (EnH) hydrolyzates from BCBs. The highest release of monosaccharides (evaluated using surface response methodology) was obtained with EnH (36.4 g/L); however, S. zooepidemicus produced more HA (1.5 g/L) using AcH compared to EnH. Hydrolyzates from acetone-extracted BCBs yielded 2.7 g/L of HA, which is similar to the amount obtained using a synthetic medium (2.8 g/L). This report demonstrates the potential of hydrolyzates from bored coffee beans to produce HA by S. zooepidemicus. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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Review

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19 pages, 3120 KiB  
Review
Lignin Biodegradation and Its Valorization
by Lingwei Cui, Zheyi Wang, Yan Zeng, Niping Yang, Mengshuang Liu, Youxi Zhao and Yanning Zheng
Fermentation 2022, 8(8), 366; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation8080366 - 30 Jul 2022
Cited by 10 | Viewed by 3617
Abstract
Lignin, a rigid polymer composed of phenolic subunits with high molecular weight and complex structure, ranks behind only cellulose in the contribution to the biomass of plants. Therefore, lignin can be used as a new environmentally friendly resource for the industrial production of [...] Read more.
Lignin, a rigid polymer composed of phenolic subunits with high molecular weight and complex structure, ranks behind only cellulose in the contribution to the biomass of plants. Therefore, lignin can be used as a new environmentally friendly resource for the industrial production of a variety of polymers, dyes and adhesives. Since laccase was found to be able to degrade lignin, increasing attention had been paid to the valorization of lignin. Research has mainly focused on the identification of lignin-degrading enzymes, which play a key role in lignin biodegradation, and the potential application of lignin degradation products. In this review, we describe the source, catalytic specificity and enzyme reaction mechanism of the four classes of the lignin-degrading enzymes so far discovered. In addition, the major pathways of lignin biodegradation and the applications of the degradative products are also discussed. Lignin-degrading bacteria or enzymes can be used in combination with chemical pretreatment for the production of value-added chemicals from lignin, providing a promising strategy for lignin valorization. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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22 pages, 1441 KiB  
Review
Net Energy Analysis and Techno-Economic Assessment of Co-Production of Bioethanol and Biogas from Cellulosic Biomass
by Teeraya Jarunglumlert and Chattip Prommuak
Fermentation 2021, 7(4), 229; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7040229 - 12 Oct 2021
Cited by 14 | Viewed by 2866
Abstract
Co-production is a process based on the biorefinery concept that maximizes the benefit of biomass by reusing residue from the production of one product to produce others. In this regard, biogas is one of the most researched second products for the production of [...] Read more.
Co-production is a process based on the biorefinery concept that maximizes the benefit of biomass by reusing residue from the production of one product to produce others. In this regard, biogas is one of the most researched second products for the production of ethanol from cellulosic biomass. However, operating this scheme requires additional investment in biogas processing equipment. This review compiles data from research studies on the co-production of bioethanol and biogas from lignocellulosic biomass to determine which is more worthwhile: leaving the residue or investing more to benefit from the second product. According to previous research, ethanol stillage can be converted to biogas via anaerobic digestion, increasing energy output by 2–3 fold. Techno-economic studies demonstrated that the co-production process reduces the minimum ethanol selling price to a level close to the market price of ethanol, implying the possibility of industrializing cellulosic ethanol production through this scheme. Full article
(This article belongs to the Special Issue Bioconversion of Lignocellulosic Materials to Value-Added Products)
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