Microbial Production of Added-value Products from Renewable Resources 2.0

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Microbial Metabolism, Physiology & Genetics".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 34285

Special Issue Editors

CICECO—Aveiro Institute of Materials, Chemistry Department, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
Interests: polyhydroxyalkanoates; mixed cultures; bioethanol; bacterial cellulose; biorefineries
Special Issues, Collections and Topics in MDPI journals
CICECO–Aveiro Institute of Materials, Chemistry Department, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro, Portugal
Interests: biorefinery; bioprocess of renewable resources for new products; bioethanol and biopolymers production; potentialities of hardwood spent sulfite liquor; laccase production, biocatalyses and immobilization; ligninolytic activity in pulp and paper industry: bleaching processes and effluent cleaning processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The world dependence on oil can generate geopolitical instability in producing countries that often results in the oscillation of its prices. Additionally, it can contribute to an increase in the economic vulnerability of non-producing countries. Moreover, the exploitation and transformation of oil, and the recalcitrance of many of its derivate products, signify an extended list of environmental problems. For these reasons, the number of research works that search for alternatives to oil as source of fuels, chemicals, and materials is increasing exponentially. Researchers are looking for new processes and raw materials that can provide the same products, or at least similar, to those obtained from oil.

In the last few decades, many microorganisms were found to be able to produce molecules that can be obtained from oil or at least substitute those in the same applications. These molecules include ethanol, butanol, lactic and succinic acids, or polyhydroxyalkanoates. Even molecules that were not produced naturally were successfully produced by microorganisms with the help of genetic engineering. Microorganisms produce these compounds using carbohydrates or organic acids as substrates. Raw materials containing carbohydrates or organic acids can be found in nature (e.g., vegetable biomass) or result from human activities (e.g., industrial wastes and sub-products). These raw materials have the advantage of being renewable and their transformation into added-value products can also signify a solution of an environmental problem.

This Special Issue intends to cover the latest and most innovative developments of this field, including all types of producing microorganisms—bacteria, fungi, and yeasts. Topics will include: The use of new raw materials; screening and isolation of novel producers; metabolic engineering for improving the production or for expanding the product range to non-endogenous producers; bioprocess design.

Prof. Dr. Luísa Seuanes Serafim
Prof. Dr. Ana Maria Rebelo Barreto Xavier
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

  • renewable resources
  • added-value products
  • microbial production
  • biorefineries
  • biofuels
  • biopolymers
  • bio-based products

Published Papers (6 papers)

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Research

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27 pages, 5001 KiB  
Article
Side-by-Side Comparison of Clean and Biomass-Derived, Impurity-Containing Syngas as Substrate for Acetogenic Fermentation with Clostridium ljungdahlii
Fermentation 2020, 6(3), 84; https://doi.org/10.3390/fermentation6030084 - 19 Aug 2020
Cited by 20 | Viewed by 2639
Abstract
Syngas, the product of biomass gasification, can play an important role in moving towards the production of renewable chemical commodities, by using acetogenic bacteria to ferment those gaseous mixtures. Due to the complex and changing nature of biomass, the composition and the impurities [...] Read more.
Syngas, the product of biomass gasification, can play an important role in moving towards the production of renewable chemical commodities, by using acetogenic bacteria to ferment those gaseous mixtures. Due to the complex and changing nature of biomass, the composition and the impurities present in the final biomass-derived syngas will vary. Because of this, it is important to assess the impact of these factors on the fermentation outcome, in terms of yields, productivity, and product formation and ratio. In this study, Clostridium ljungdahlii was used in a fed-batch fermentation system to analyze the effect of three different biomass-derived syngases, and to compare them to equivalent, clean syngas mixtures. Additionally, four other clean syngas mixtures were used, and the effects on product ratio, productivity, yield, and growth were documented. All biomass-derived syngases were suitable to be used as substrates, without experiencing any complete inhibitory effects. From the obtained results, it is clear that the type of syngas, biomass-derived or clean, had the greatest impact on product formation ratios, with all biomass-derived syngases producing more ethanol, albeit with lesser total productivity. Full article
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14 pages, 998 KiB  
Article
Combining Xylose Reductase from Spathaspora arborariae with Xylitol Dehydrogenase from Spathaspora passalidarum to Promote Xylose Consumption and Fermentation into Xylitol by Saccharomyces cerevisiae
Fermentation 2020, 6(3), 72; https://doi.org/10.3390/fermentation6030072 - 21 Jul 2020
Cited by 12 | Viewed by 3281
Abstract
In recent years, many novel xylose-fermenting yeasts belonging to the new genus Spathaspora have been isolated from the gut of wood-feeding insects and/or wood-decaying substrates. We have cloned and expressed, in Saccharomyces cerevisiae, a Spathaspora arborariae xylose reductase gene (SaXYL1) [...] Read more.
In recent years, many novel xylose-fermenting yeasts belonging to the new genus Spathaspora have been isolated from the gut of wood-feeding insects and/or wood-decaying substrates. We have cloned and expressed, in Saccharomyces cerevisiae, a Spathaspora arborariae xylose reductase gene (SaXYL1) that accepts both NADH and NADPH as co-substrates, as well as a Spathaspora passalidarum NADPH-dependent xylose reductase (SpXYL1.1 gene) and the SpXYL2.2 gene encoding for a NAD+-dependent xylitol dehydrogenase. These enzymes were co-expressed in a S. cerevisiae strain over-expressing the native XKS1 gene encoding xylulokinase, as well as being deleted in the alkaline phosphatase encoded by the PHO13 gene. The S. cerevisiae strains expressing the Spathaspora enzymes consumed xylose, and xylitol was the major fermentation product. Higher specific growth rates, xylose consumption and xylitol volumetric productivities were obtained by the co-expression of the SaXYL1 and SpXYL2.2 genes, when compared with the co-expression of the NADPH-dependent SpXYL1.1 xylose reductase. During glucose-xylose co-fermentation by the strain with co-expression of the SaXYL1 and SpXYL2.2 genes, both ethanol and xylitol were produced efficiently. Our results open up the possibility of using the advantageous Saccharomyces yeasts for xylitol production, a commodity with wide commercial applications in pharmaceuticals, nutraceuticals, food and beverage industries. Full article
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21 pages, 3135 KiB  
Article
Evaluation of Media Components and Process Parameters in a Sensitive and Robust Fed-Batch Syngas Fermentation System with Clostridium ljungdahlii
Fermentation 2020, 6(2), 61; https://doi.org/10.3390/fermentation6020061 - 18 Jun 2020
Cited by 20 | Viewed by 3578
Abstract
The fermentation of synthesis gas, or syngas, by acetogenic bacteria can help in transitioning from a fossil-fuel-based to a renewable bioeconomy. The main fermentation products of Clostridium ljungdahlii, one of such microorganisms, are acetate and ethanol. A sensitive, robust and reproducible system [...] Read more.
The fermentation of synthesis gas, or syngas, by acetogenic bacteria can help in transitioning from a fossil-fuel-based to a renewable bioeconomy. The main fermentation products of Clostridium ljungdahlii, one of such microorganisms, are acetate and ethanol. A sensitive, robust and reproducible system was established for C. ljungdahlii syngas fermentation, and several process parameters and medium components (pH, gas flow, cysteine and yeast extract) were investigated to assess its impact on the fermentation outcomes, as well as real time gas consumption. Moreover, a closed carbon balance could be achieved with the data obtained. This system is a valuable tool to detect changes in the behavior of the culture. It can be applied for the screening of strains, gas compositions or media components, for a better understanding of the physiology and metabolic regulation of acetogenic bacteria. Here, it was shown that neither yeast extract nor cysteine was a limiting factor for cell growth since their supplementation did not have a noticeable impact on product formation or overall gas consumption. By combining the lowering of both the pH and the gas flow after 24 h, the highest ethanol to acetate ratio was achieved, but with the caveat of lower productivity. Full article
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9 pages, 347 KiB  
Article
Ethanol Production from Cheese Whey and Expired Milk by the Brown Rot Fungus Neolentinus lepideus
Fermentation 2019, 5(2), 49; https://doi.org/10.3390/fermentation5020049 - 16 Jun 2019
Cited by 23 | Viewed by 8853
Abstract
The basidiomycete brown rot fungus Neolentinus lepideus is capable of assimilating and fermenting lactose to ethanol with a conversion yield comparable to those of lactose-fermenting yeasts. The ability of the fungus to ferment lactose is not influenced by the addition of glucose or [...] Read more.
The basidiomycete brown rot fungus Neolentinus lepideus is capable of assimilating and fermenting lactose to ethanol with a conversion yield comparable to those of lactose-fermenting yeasts. The ability of the fungus to ferment lactose is not influenced by the addition of glucose or calcium. Therefore, N. lepideus may be useful in ethanol production from materials composed mainly of lactose, such as cheese whey or expired cow’s milk. Whey is a by-product of cheese manufacturing, and approximately 50% of the total worldwide production of whey is normally disposed of without being utilized. We found that N. lepideus produced ethanol directly from cheese whey with a yield of 0.35 g of ethanol per gram of lactose consumed, and it also fermented expired milk containing lactose, protein, and fat with a similar yield. Our findings revealed that the naturally occurring basidiomycete fungus possesses a unique ability to produce ethanol from cheese whey and expired milk. Thus, N. lepideus may be useful in facilitating ethanol production from dairy wastes in a cost-effective and environmentally friendly manner. Full article
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11 pages, 1738 KiB  
Article
Glycosylceramides Purified from the Japanese Traditional Non-Pathogenic Fungus Aspergillus and Koji Increase the Expression of Genes Involved in Tight Junctions and Ceramide Delivery in Normal Human Epidermal Keratinocytes
Fermentation 2019, 5(2), 43; https://doi.org/10.3390/fermentation5020043 - 24 May 2019
Cited by 13 | Viewed by 4469
Abstract
Koji, which is used for manufacturing Japanese traditional fermented foods, has long been safely used as a cosmetic product. Although its cosmetic effect has been empirically established, the underlying mechanism has not been reported. We and other groups have previously elucidated that [...] Read more.
Koji, which is used for manufacturing Japanese traditional fermented foods, has long been safely used as a cosmetic product. Although its cosmetic effect has been empirically established, the underlying mechanism has not been reported. We and other groups have previously elucidated that koji contains glycosylceramides, including N-2′-hydroxyoctadecanoyl-1-O-β-d-glucosyl-9-methyl-4,8-sphingadienine and N-2′-hydroxyoctadecanoyl-1-O-β-d-galactosyl-9-methyl-4,8-sphingadienine. This led us to hypothesise that koji exerts its cosmetic effect by acting on the keratinocytes through glycosylceramides on the gene level. Therefore, in this study, we investigated the effects of glycosylceramides from various sources on gene expression in normal human epidermal keratinocytes. The results revealed that glycosylceramides purified from white koji and the white koji-producing non-pathogenic fungus Aspergillus luchuensis and A. oryzae increased the expression of occludin (OCLN, an epidermal tight junction protein) and ATP-binding cassette sub-family A member 12 (ABCA12, a cellular membrane transporter), albeit the effect was modest relative to that of ceramides. Indeed, ceramide was increased in the keratinocytes upon koji lipid extract addition. These results indicate that glycosylceramides, which are the major sphingolipids of most natural materials, have an effect of increasing ABCA12 and OCLN expression, and suggest that koji exerts its cosmetic effect by increasing ceramide and tight junctions via glycosylceramides. Full article
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Review

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16 pages, 323 KiB  
Review
By-Products in the Malting and Brewing Industries—Re-Usage Possibilities
Fermentation 2020, 6(3), 82; https://doi.org/10.3390/fermentation6030082 - 08 Aug 2020
Cited by 49 | Viewed by 10382
Abstract
Beer production includes the formation of different by-products such as wastewater, spent grains, spent hops, and yeast. In addition to these well-known by-products, it is necessary to mention germ/rootlets, which also remain after the malting process. Given that a huge amount of beer [...] Read more.
Beer production includes the formation of different by-products such as wastewater, spent grains, spent hops, and yeast. In addition to these well-known by-products, it is necessary to mention germ/rootlets, which also remain after the malting process. Given that a huge amount of beer is produced annually worldwide, by-products are available in large quantities throughout the year. Spent grains, spent hops, and spent yeasts are high-energy raw materials that possess a great potential for application in the branch of biotechnology, and the food industry, but these by-products are commonly used as livestock feed, disposed of in the fields, or incinerated. Breweries by-products can be utilized for microalgae production, biofuel production, extraction of proteins, polyphenolic, antioxidative substances, etc. This paper aims to address each of these by-products with an emphasis on their possible application in biotechnology and other industries. Full article
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