Special Issue "Biomass Conversion: Fermentation Chemicals and Fuels"

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

Deadline for manuscript submissions: closed (31 October 2020).

Special Issue Editor

Dr. Konstantinos G. Kalogiannis
E-Mail Website
Guest Editor
Center For Research And Technology - Hellas, Chemical Process and Energy Resources Institute, Thessaloniki, Greece
Interests: biorefineries; biofuels; delignification and fractionation technologies; biomass and wastes valorization; pyrolysis; heterogeneous catalysis; thermochemical conversion technologies

Special Issue Information

Dear Colleagues,

Lignocellulosic biomass, especially in the form of waste residues such as those produced in the agriculture and forestry industries, has garnered significant attention in recent years for the production of fuels and high added value chemicals. It is a sustainable and renewable source of carbon and hydrogen, and is therefore suitable to replace fossil resources, which has promoted the concept of the bio-refinery. Analogous to the conventional refinery, the bio-refinery seeks to fractionate the initial lignocellulosic feedstock into its main constituents: cellulose, hemicellulose, and lignin. Each one has unique chemistry, and therefore different chemical processes need to be developed for their efficient conversion to traditional and novel chemicals and fuels that will replace the fossil-derived ones.

The biochemical transformation of lignocellulosic biomass, employing enzymes and microorganisms found in nature and drawing inspiration from our ecosystem, is emerging as an important tool in bio-refinery technology. It has significant advantages, such as high selectivity and low production of toxic by-products, low energy requirements, and it requires water as a solvent and is therefore an extremely green process. However, significant challenges also need to be addressed. Enzymes are still expensive, efficient pretreatment of the biomass is needed in order to efficiently convert its fractions, and biochemical reactions can be slow, significantly increasing reactor sizes.

Nevertheless, the added value of fermentation processes is unequivocal. Fermentation can produce fuels in the form of alcohols, chemicals such as lactic and succinic acid that are the building blocks for novel polymers, phenols and phenol oligomers with targeted functionalities that are derived from lignin—the only renewable source of aromatic rings in abundance. Moreover, high added value products are especially interesting, such as food additives in the form of prebiotics and omega-3 fatty acids derived from microalgae or nanoparticles of lignin and cellulose, which are products with increased functionalities.

This Special Issue aims to highlight the emerging role of fermentation in the production of traditional and novel products and to underline the key challenges that arise in this demanding yet fulfilling research area.

Dr. Konstantinos G. Kalogiannis
Guest Editor

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 papers will be 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 quarterly 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 1600 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

  • fermentation
  • biocatalysis
  • lignocellulosic biomass
  • platform chemicals
  • enzymatic hydrolysis
  • saccharification
  • green chemistry
  • pretreatment
  • chemical building blocks
  • fuels

Published Papers (13 papers)

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Editorial

Jump to: Research, Review

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 515
Abstract
Rendezvous with Rama [...] Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)

Research

Jump to: Editorial, Review

Article
Evaluation of Basidiomycetes Wild Strains Grown in Agro-Industrial Residues for Their Anti-Tyrosinase and Antioxidant Potential and for the Production of Biocatalysts
Fermentation 2021, 7(1), 19; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7010019 - 01 Feb 2021
Cited by 1 | Viewed by 1003
Abstract
White-rot basidiomycetes are the only microorganisms with the ability to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for degrading cellulose/hemicellulose and lignin. In addition, they produce biologically active natural products with important application in cosmetic formulations, either as pure compounds [...] Read more.
White-rot basidiomycetes are the only microorganisms with the ability to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for degrading cellulose/hemicellulose and lignin. In addition, they produce biologically active natural products with important application in cosmetic formulations, either as pure compounds or as standardized extracts. In the present work, three wild strains of Basidiomycetes fungi (Pleurotus citrinopileatus, Abortiporus biennis and Ganoderma resinaceum) from Greek habitats were grown in agro-industrial residues (oil mill wastewater, and corn cob) and evaluated for their anti-tyrosinase and antioxidant activity and for the production of biotechnologically relevant enzymes. P. citrinopileatus showed the most interesting tyrosinase inhibitory activity, while A. biennis showed the highest DPPH(2,2-diphenyl-1-picryl-hydrazyl) scavenging potential. Corn cobs were the most appropriate carbon source for maximizing the inhibitory effect of fungal biomasses on both activities, while the use of oil mill wastewater selectively increased the anti-tyrosinase potential of P. citrinopileatus culture filtrate. All strains were found to be preferential lignin degraders, similarly to most white-rot fungi. Bioinformatic analyses were performed on the proteome of the strains P. citrinopileatus and A. biennis, focusing on CAZymes with biotechnological relevance, and the results were compared with the enzyme activities of culture supernatants. Overall, all three strains showed strong production of oxidative enzymes for biomass conversion applications. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Upcycling of Whey Permeate through Yeast- and Mold-Driven Fermentations under Anoxic and Oxic Conditions
Fermentation 2021, 7(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation7010016 - 26 Jan 2021
Cited by 3 | Viewed by 1233
Abstract
Dairy manufacturing generates whey by-products, many of them considered waste; others, such as whey permeate, a powder high in lactose and minerals from deproteinated whey, have unrealized potential. This study identified yeast species capable of utilizing lactose from whey permeate to produce ethanol [...] Read more.
Dairy manufacturing generates whey by-products, many of them considered waste; others, such as whey permeate, a powder high in lactose and minerals from deproteinated whey, have unrealized potential. This study identified yeast species capable of utilizing lactose from whey permeate to produce ethanol or organic acids, and identified fungal species that reduced the acidity of whey by-products. Reconstituted whey permeate was fermented anaerobically or aerobically for 34 days, using species from Cornell University’s Food Safety Lab, Alcaine Research Group, and Omega Labs. Yeast species: Kluyveromyces marxianus, Kluyveromyces lactis, Dekkera anomala, Brettanomyces claussenii, Brettanomyces bruxellensis; mold species: Mucor genevensis and Aureobasidium pullulans. Density, pH, cell concentrations, organic acids, ethanol, and sugar profiles were monitored. Under anoxic conditions, K. marxianus exhibited the greatest lactose utilization and ethanol production (day 20: lactose non-detectable; 4.52% ± 0.02 ethanol). Under oxic conditions, D. anomala produced the most acetic acid (day 34: 9.18 ± 3.38 g/L), and A. pullulans utilized the most lactic acid, increasing the fermentate’s pH (day 34: 0.26 ± 0.21 g/L, pH: 7.91 ± 0.51). This study demonstrates that fermentation of whey could produce value-added alcoholic or organic acid beverages, or increase the pH of acidic by-products, yielding new products and increasing sustainability. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Conversion of Xylose from Birch Hemicellulose Hydrolysate to 2,3-Butanediol with Bacillus vallismortis
Fermentation 2020, 6(3), 86; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation6030086 - 02 Sep 2020
Cited by 5 | Viewed by 812
Abstract
Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals, such as butadiene or methyl ethyl ketone, which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk class 2 microorganisms and pure [...] Read more.
Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals, such as butadiene or methyl ethyl ketone, which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk class 2 microorganisms and pure glucose as substrate. However, as glucose stays in competition to food and feed industries, a lot of effort has been done in the last years finding efficient alternative substrates. Thereby xylose from hydrolysed wood hemicelluloses is a promising substrate for the production of 2,3-BDO. The risk class 1 microorganism Bacillus vallismortis strain was identified as a very promising 2,3-BDO producer. The strain is able to utilize xylose almost in the same manner as glucose. B. vallismortis is less prone to common inhibiting compounds in lignocellulosic extracts/hydrolysates. When using a concentrated hemicellulose fraction from birch wood hydrolysate, which was produced with ultrafiltration and after which the acetate concentration was reduced, a yield of 0.43 g g−1 was achieved and the xylose consumption and the 2,3-BDO production is basically the same as using pure xylose. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Evaluation of Filamentous Fungal Biomass Cultivated on Vinasse as an Alternative Nutrient Source of Fish Feed: Protein, Lipid, and Mineral Composition
Fermentation 2019, 5(4), 99; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5040099 - 02 Dec 2019
Cited by 22 | Viewed by 3313
Abstract
The rapid growth of aquaculture and scarcity of conventional fish feed supplements has prompted the introduction of new sustainable supplementation sources. In this study, the potential of five strains of fungal biomass of Ascomycetes and Zygomycetes edible filamentous fungi, Aspergillus oryzae, Neurospora [...] Read more.
The rapid growth of aquaculture and scarcity of conventional fish feed supplements has prompted the introduction of new sustainable supplementation sources. In this study, the potential of five strains of fungal biomass of Ascomycetes and Zygomycetes edible filamentous fungi, Aspergillus oryzae, Neurospora intermedia, Rizhopus oryzae, Monascus purpureus, and Fusarium venenatum, cultivated on vinasse, a by-product of the bioethanol industry, as alternative protein sources for fishmeal in the fish diet was evaluated. It was observed that 5% vinasse with an initial pH of 5–6.5 can support fungal biomass yields of 34.3 ± 2.4–118.5 ± 3.9 g DM/L for A. Oryzae, N. intermedia, and R. oryzae. High protein contents of about 44.7%, 57.6%, and 50.9% (w/w), and fat contents of 7.0%, 3.5%, and 5.5% (w/w) were obtained for A. oryzae, N. intermedia, and R. oryzae, respectively. The latter three fungi species contained noticeable amino acid contents, including promising profiles of amino acids that are highly compatible with those of fishmeal. These findings provide evidence that fungal biomasses, with their relatively high protein content, good amino acid profiles, and other essential nutrients, are a promising supplementation alternative that can be produced from low-value by-products and organic-rich waste streams like vinasse to meet the dietary protein requirements in fish feed. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Pretreatment of Sweet Sorghum Bagasse for Ethanol Production Using Na2CO3 Obtained by NaOH Absorption of CO2 Generated in Sweet Sorghum Juice Ethanol Fermentation
Fermentation 2019, 5(4), 91; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5040091 - 24 Oct 2019
Cited by 1 | Viewed by 1324
Abstract
(1) Background: Commercial production of fuel ethanol currently uses sugarcane and corn as feedstocks. Attempts to develop other renewable feedstocks that are more abundant have led to lignocellulosic biomass, which requires pretreatment prior to enzymatic hydrolysis to generate fermentable sugars. One of the [...] Read more.
(1) Background: Commercial production of fuel ethanol currently uses sugarcane and corn as feedstocks. Attempts to develop other renewable feedstocks that are more abundant have led to lignocellulosic biomass, which requires pretreatment prior to enzymatic hydrolysis to generate fermentable sugars. One of the largest cost components of pretreatment is chemical cost. Ethanol fermentation also produces large quantities of CO2 as a co-product contributing to global warming. (2) Methods: Sweet sorghum has emerged as a potential new feedstock for ethanol production. In the present study, the CO2 produced in sweet sorghum juice (SSJ) fermentation was captured by absorption in 5 M NaOH. The resultant Na2CO3 solution was used for pretreatment of sweet sorghum bagasse (SSB), which is the solid residue in SSJ extraction. The pretreated SSB was fermented in SSJ to produce additional ethanol. (3) Results: CO2 absorption efficiency of 92.0% was observed. Pretreatment of SSB by the obtained Na2CO3 solution resulted in no loss of glucan and only 8.1 wt% loss of xylan. Ethanol yield from glucan in the pretreated SSB was 81.7% theoretical. (4) Conclusions: CO2 from SSJ fermentation captured as Na2CO3 could be used for efficient SSB pretreatment. Further study focusing on pretreatment process optimization is needed. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Investigation and Modeling of Gas-Liquid Mass Transfer in a Sparged and Non-Sparged Continuous Stirred Tank Reactor with Potential Application in Syngas Fermentation
Fermentation 2019, 5(3), 75; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5030075 - 13 Aug 2019
Cited by 6 | Viewed by 2260
Abstract
Syngas (mixture of CO, H2 and CO2) fermentation suffers from mass transfer limitation due to low solubility of CO and H2 in the liquid medium. Therefore, it is critical to characterize the mass transfer in syngas fermentation reactors to [...] Read more.
Syngas (mixture of CO, H2 and CO2) fermentation suffers from mass transfer limitation due to low solubility of CO and H2 in the liquid medium. Therefore, it is critical to characterize the mass transfer in syngas fermentation reactors to guide in delivery of syngas to the microorganisms. The objective of this study is to measure and predict the overall volumetric mass transfer coefficient, kLa for O2 at various operating conditions in a 7-L sparged and non-sparged continuous stirred-tank reactor (CSTR). Measurements indicated that the kLa for O2 increased with an increase in air flow rate and agitation speed. However, kLa for O2 decreased with the increase in the headspace pressure. The highest kLa for O2 with air sparged in the CSTR was 116 h−1 at 600 sccm, 900 rpm, 101 kPa, and 3 L working volume. Backmixing of the headspace N2 in the sparged CSTR reduced the observed kLa. The mass transfer model predicted the kLa for O2 within 10% of the experimental values. The model was extended to predict the kLa for syngas components CO, CO2 and H2, which will guide in selecting operating conditions that minimize power input to the bioreactor and maximize the syngas conversion efficiency. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Effect of N2 on Biological Methanation in a Continuous Stirred-Tank Reactor with Methanothermobacter marburgensis
Fermentation 2019, 5(3), 56; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5030056 - 02 Jul 2019
Cited by 4 | Viewed by 1966
Abstract
In this contribution, the effect of the presence of a presumed inert gas like N2 in the feed gas on the biological methanation of hydrogen and carbon dioxide with Methanothermobacter marburgensis was investigated. N2 can be found as a component besides [...] Read more.
In this contribution, the effect of the presence of a presumed inert gas like N 2 in the feed gas on the biological methanation of hydrogen and carbon dioxide with Methanothermobacter marburgensis was investigated. N 2 can be found as a component besides CO 2 in possible feed gases like mine gas, weak gas, or steel mill gas. To determine whether there is an effect on the biological methanation of CO 2 and H 2 from renewable sources or not, the process was investigated using feed gases containing CO 2 , H 2 , and N 2 in different ratios, depending on the CO 2 content. A possible effect can be a lowered conversion rate of CO 2 and H 2 to CH 4 . Feed gases containing up to 47% N 2 were investigated. The conversion of hydrogen and carbon dioxide was possible with a conversion rate of up to 91% but was limited by the amount of H 2 when feeding a stoichiometric ratio of 4:1 and not by adding N 2 to the feed gas. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Kinetic Study on Heterotrophic Growth of Acetobacterium woodii on Lignocellulosic Substrates for Acetic Acid Production
Fermentation 2019, 5(1), 17; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5010017 - 02 Feb 2019
Cited by 8 | Viewed by 1897
Abstract
Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic [...] Read more.
Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic feedstocks-derived sugars as substrates. In this study, we examine the growth kinetics and acetic acid production of A. woodii on glucose and xylose. While good growth was observed with glucose as substrate, no significant growth was obtained on xylose. Kinetic studies were performed in batch culture using different concentrations of glucose, ranging from 5 g/L to 40 g/L. The highest acetate production of 6.919 g/L with a product yield of 0.76 g acetic acid/g glucose was observed with 10 g/L glucose as initial substrate concentration. When testing A. woodii on corn stover hydrolysate (CSH) and wheat straw hydrolysate (WSH) formed after pretreatment and enzymatic hydrolysis, we found that A. woodii showed acetic acid production of 7.64 g/L and a product yield of 0.70 g acetic acid/g of glucose on WSH, while the acetic acid production was 7.83 g/L with a product yield of 0.65 g acetic acid/g of glucose on CSH. These results clearly demonstrate that A. woodii performed similarly on pure substrates and hydrolysates, and that the processes were not inhibited by the heterogenous components present in the lignocellulosic feedstock hydrolysates. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Effects of Ultrasound on Fermentation of Glucose to Ethanol by Saccharomyces cerevisiae
Fermentation 2019, 5(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5010016 - 29 Jan 2019
Cited by 7 | Viewed by 2752
Abstract
Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial [...] Read more.
Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial and inhibitory effects. In this study, the effects of ultrasound on mass transfer limitations during fermentation were examined. Calculation of the external and intraparticle observable moduli under a range of conditions indicate that no external or intraparticle mass transfer limitations should exist for the mass transfer of glucose, ethanol, or carbon dioxide. Fermentations of glucose to ethanol using Saccharomyces cerevisiae were conducted at different ultrasound intensities to examine its effects on glucose uptake, ethanol production, and yeast population and viability. Four treatments were compared: direct ultrasound at intensities of 23 and 32 W/L, indirect ultrasound (1.4 W/L), and no-ultrasound. Direct and indirect ultrasound had negative effects on yeast performance and viability, and reduced the rates of glucose uptake and ethanol production. These results indicate that ultrasound during fermentation, at the levels applied, is inhibitory and not expected to improve mass transfer limitations. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Article
Effect of Various Pretreatment Methods on Bioethanol Production from Cotton Stalks
Fermentation 2019, 5(1), 5; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation5010005 - 01 Jan 2019
Cited by 33 | Viewed by 2449
Abstract
Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken [...] Read more.
Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken to investigate the effect of various chemical and physicochemical pretreatment methods, i.e., alkali, microwave-assisted acid, organosolv, hydrothermal treatment, and sequentially organosolv and hydrothermal pretreatment, on chemical composition of CS and subsequent ethanol production applying pre-hydrolysis and simultaneous saccharification and fermentation (PSSF) at high solid loading. The best results in terms of ethanol production were achieved by the sequential combination of organosolv and hydrothermal pretreatment (32.3 g/L, using 15% w/v substrate concentration and 6 h pre-hydrolysis) with an improvement of 32% to 50% in ethanol production compared to the other pretreatments. Extending pre-hydrolysis time to 14 h and increasing substrate concentration to 20% w/v, ethanol production reached 47.0 g/L (corresponding to an ethanol yield of 52%) after 30 h of fermentation. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Review

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Review
Fermentation as an Alternative Process for the Development of Bioinsecticides
Fermentation 2020, 6(4), 120; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation6040120 - 08 Dec 2020
Viewed by 1013
Abstract
Currently, insect pest control is carried out through the application of synthetic insecticides which have been related to harmful effects on both human and environmental health, as well as to the development of resistant pest populations. In this context, the development of new [...] Read more.
Currently, insect pest control is carried out through the application of synthetic insecticides which have been related to harmful effects on both human and environmental health, as well as to the development of resistant pest populations. In this context, the development of new and natural insecticides is necessary. Agricultural and forestry waste or by-products are very low-cost substrates that can be converted by microorganisms into useful value-added bioactive products through fermentation processes. In this review we discuss recent discoveries of compounds obtained from fermented substrates along with their insecticidal, antifeedant, and repellent activities. Fermentation products obtained from agricultural and forestry waste are described in detail. The fermentation of the pure secondary metabolite such as terpenes and phenols is also included. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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Review
The Effects of Halogenated Compounds on the Anaerobic Digestion of Macroalgae
Fermentation 2020, 6(3), 85; https://0-doi-org.brum.beds.ac.uk/10.3390/fermentation6030085 - 27 Aug 2020
Cited by 2 | Viewed by 1165
Abstract
The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, [...] Read more.
The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, unlike terrestrial plants, produce a range of halogenated secondary metabolites, especially chlorinated and brominated compounds. Some orders of brown seaweeds also accumulate iodine, up to 1.2% of their dry weight. Fluorine remains rather unusual within the chemical structure. Halogenated hydrocarbons have moderate to high toxicities. In addition, halogenated organic compounds constitute a large group of environmental chemicals due to their extensive use in industry and agriculture. In recent years, concerns over the environmental fate and release of these halogenated organic compounds have resulted in research into their biodegradation and the evidence emerging shows that many of these compounds are more easily degraded under strictly anaerobic conditions compared to aerobic biodegradation. Biosorption via seaweed has become an alternative to the existing technologies in removing these pollutants. Halogenated compounds are known inhibitors of methane production from ruminants and humanmade anaerobic digesters. The focus of this paper is reviewing the available information on the effects of halogenated organic compounds on anaerobic digestion. Full article
(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)
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