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Biomass Conversion to Biofuels
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Biomass Conversion to Biofuels

A special issue of Fuels (ISSN 2673-3994).

Deadline for manuscript submissions: 15 January 2025 | Viewed by 25202

Special Issue Editor

Prof. Dr. Mamoru Yamada

E-Mail Website
Guest Editor
Department of Biological Chemistry, Faculty of Agriculture, Life Science, Graduate School of Science and Technology for Innovation and Research Center for Thermotolerant Microbial Resources, Yamaguchi University, Yamaguchi, Japan
Interests: biomass conversion to useful materials including biofuels; low-cost fermentation; stress-resistant fermenting microbes; mutation and genomic modification

Special Issue Information

Dear Colleagues,

Bioconversion of biomass to useful materials is strongly recommended under global warming, but is still inefficient and costly, especially for cellulosic biomass. The worldwide demand for biofuels is growing rapidly, and technological development for producing biofuels efficiently and at low cost from various types of biomass is an urgent issue. Thus, the development of new technologies and the creation of basic knowledge for “Biomass Conversion to Fuels” are indispensable and will contribute to the transition to a sustainable development society.

This topic includes basic to applied researches relating to “Biomass Conversion to Fuels;” for example, treatment of biomass materials, enzymatic hydrolysis of polysaccharides, efficient fermentation by newly isolated microbes, enhancement of microbial stress tolerance including heat resistance, mechanism of stress tolerance, metabolic engineering, synthetic biology, consolidated fermentation, high temperature fermentation, and combination with downstream processes.

Prof. Dr. Mamoru Yamada
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 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. Fuels 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 1000 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.

Published Papers (7 papers)

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Research

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15 pages, 3088 KiB  
Article
Mutants with Enhanced Multi-Stress Tolerance of Kluyveromyces marxianus and Their Ability for Ethanol Fermentation
by Noppon Lertwattanasakul, Sornsiri Pattanakittivorakul, Sukanya Nitiyon, Minenosuke Matsutani, Akihiro Oguchi, Katsushi Hirata, Tomoyuki Kosaka, Savitree Limtong and Mamoru Yamada
Fuels 2023, 4(4), 469-483; https://doi.org/10.3390/fuels4040029 - 30 Nov 2023
Cited by 1 | Viewed by 1028
Abstract
Kluyveromyces marxianus is an attractive thermotolerant yeast species for ethanol production because of its ability to utilize various carbon sources as a fermentation substrate. The use of thermotolerant microorganisms enables the performance of high-temperature ethanol fermentation, which has several advantages, including the reduction [...] Read more.
Kluyveromyces marxianus is an attractive thermotolerant yeast species for ethanol production because of its ability to utilize various carbon sources as a fermentation substrate. The use of thermotolerant microorganisms enables the performance of high-temperature ethanol fermentation, which has several advantages, including the reduction of cooling costs and minimization of contamination risks. To improve K. marxianus for ethanol fermentation under stress conditions, two strains, DMKU 3-1042 and DMKU 3-118, were adapted for heat resistance and resistance to toxic substances in pulp wastewater from a paper mill, respectively, resulting in the generation of KMR1042 and KMR118, respectively. Both adapted mutants exhibited clumpy clusters of cells as pseudo-hyphae and altered colony morphology, and their sedimentation speeds were much faster than those of the corresponding parent strains. The two mutants showed stronger tolerance to various stresses and higher performance for ethanol production than those of the corresponding parent strains at high temperatures or in the presence of toxic substances. Genome sequencing analysis revealed that both mutants had disruption of the same gene, SWI5, despite adaptation under different stress conditions, suggesting that the formation of pseudo-hyphae is a common strategy of K. marxianus for coping with stresses. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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13 pages, 16548 KiB  
Article
Mutants with Enhanced Cellobiose-Fermenting Ability from Thermotolerant Kluyveromyces marxianus DMKU 3-1042, Which Are Beneficial for Fermentation with Cellulosic Biomass
by Masayuki Murata, Sornsiri Pattanakittivorakul, Toshiro Manabe, Savitree Limtong and Mamoru Yamada
Fuels 2022, 3(2), 232-244; https://doi.org/10.3390/fuels3020015 - 29 Apr 2022
Cited by 3 | Viewed by 2046
Abstract
Several cellulose-hydrolysis enzymes are required for eco-friendly utilization of cellulose as renewable biomass, and it would therefore be beneficial if fermenting microbes can provide such enzymes without genetic engineering. Thermotolerant and multisugar-fermenting Kluyveromyces marxianus is one of the promising yeasts for high-temperature fermentation [...] Read more.
Several cellulose-hydrolysis enzymes are required for eco-friendly utilization of cellulose as renewable biomass, and it would therefore be beneficial if fermenting microbes can provide such enzymes without genetic engineering. Thermotolerant and multisugar-fermenting Kluyveromyces marxianus is one of the promising yeasts for high-temperature fermentation and has genes for putative oligosaccharide-degradation enzymes. Mutants obtained after multiple mutagenesis showed significantly higher activity than that of the parental strain for cellobiose fermentation. The efficient strains were found to have amino acid substitutions and frame-shift mutations in 26-28 genes including 3 genes for glucose transporters. These strains grown in a cellobiose medium showed higher β-glucosidase than that of the parental strain and greatly reduced glucose utilization. The introduction of KTH2 for a glucose transporter into one of the efficient mutants reduced the cellobiose fermentation activity of the mutant. The results suggest that release from glucose repression significantly promotes the uptake of cellobiose. Co-culture of one efficient strain and the parental strain allowed good fermentation of both glucose and cellobiose, suggesting that the efficient strains are useful for conversion of cellulosic biomass to ethanol. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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13 pages, 3094 KiB  
Article
Application of Zeolite Membranes to Dehydrate a Bio-Ethanol Solution Produced by High-Temperature Fermentation
by Izumi Kumakiri, Yusuke Maruo, Ryotaro Kishibe, Masayuki Murata, Tomoyuki Kosaka and Mamoru Yamada
Fuels 2021, 2(4), 533-545; https://doi.org/10.3390/fuels2040031 - 03 Dec 2021
Cited by 2 | Viewed by 2657
Abstract
The combination of high-temperature fermentation and membrane separation has the potential to realize a simple on-site process to produce concentrated bioethanol. The performance of dehydration membranes in separating bioethanol was investigated in this study. Three types of zeolite membranes, LTA, MFI, and MOR, [...] Read more.
The combination of high-temperature fermentation and membrane separation has the potential to realize a simple on-site process to produce concentrated bioethanol. The performance of dehydration membranes in separating bioethanol was investigated in this study. Three types of zeolite membranes, LTA, MFI, and MOR, were synthesized. Their dehydration ability was compared using a bioethanol solution produced by high-temperature fermentation followed by vacuum distillation. The LTA zeolite membranes deformed and became amorphous while treating the distillate. On the contrary, no significant changes were observed in the MFI and MOR zeolite membranes analyzed by X-ray diffraction after treating the distillate. However, the flux declined when the membranes were in contact with the distillate (pH = 3.8). Neutralizing the distillate to pH 6.6 with sodium hydroxide did not prevent the flux decline. Even though flux decreased by about 20–30%, the MOR membrane showed quite high water-selectivity, with a water concentration of over 99.9% in the permeate, suggesting the feasibility of its application to concentrate bioethanol. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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12 pages, 842 KiB  
Article
Mixotrophic Cultivation of Microalgae in Cassava Processing Wastewater for Simultaneous Treatment and Production of Lipid-Rich Biomass
by Vanessa Ghiggi Sorgatto, Carlos Ricardo Soccol, Denisse Tatiana Molina-Aulestia, Marco Aurélio de Carvalho, Gilberto Vinícius de Melo Pereira and Júlio Cesar de Carvalho
Fuels 2021, 2(4), 521-532; https://doi.org/10.3390/fuels2040030 - 01 Dec 2021
Cited by 4 | Viewed by 2796
Abstract
Cassava processing wastewater (CPW) is a highly polluting, liquid residue of cassava processing, usually discarded or treated anaerobically. However, it can serve as a low-cost culture medium for microalgae. After a preliminary evaluation of the growth of 10 microalgal strains in diluted CPW, [...] Read more.
Cassava processing wastewater (CPW) is a highly polluting, liquid residue of cassava processing, usually discarded or treated anaerobically. However, it can serve as a low-cost culture medium for microalgae. After a preliminary evaluation of the growth of 10 microalgal strains in diluted CPW, the microalgae Haematococcus pluvialis SAG 34−1b and Neochloris (Ettlia) oleoabundans UTEX 1185 were selected for cultivation in CPW without a supply of additional nutrients and evaluated for their growth, lipid production, and nutrients removal. Maximal biomass concentrations of 1.79 g·L−1 for H. pluvialis and 3.18 g·L−1 for N. oleoabundans were achieved with 25% CPW medium on the 13th day of growth. The algae H. pluvialis and N. oleoabundans removed 60.80 and 69.16% of the chemical oxygen demand, 51.06 and 58.19% of total nitrate, and 54.68 and 69.84% of phosphate, respectively. On average, lipid productivities reached 0.018 and 0.041 g·L−1 day−1 for H. pluvialis and N. oleoabundans, respectively. Therefore, cultivating these microalgae in diluted CPW is a promising treatment for cassava wastewater with simultaneous valuable biomass production. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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12 pages, 2723 KiB  
Article
Extremely Halophilic Biohydrogen Producing Microbial Communities from High-Salinity Soil and Salt Evaporation Pond
by Dyah Asri Handayani Taroepratjeka, Tsuyoshi Imai, Prapaipid Chairattanamanokorn and Alissara Reungsang
Fuels 2021, 2(2), 241-252; https://doi.org/10.3390/fuels2020014 - 10 Jun 2021
Cited by 2 | Viewed by 2898
Abstract
Extreme halophiles offer the advantage to save on the costs of sterilization and water for biohydrogen production from lignocellulosic waste after the pretreatment process with their ability to withstand extreme salt concentrations. This study identifies the dominant hydrogen-producing genera and species among the [...] Read more.
Extreme halophiles offer the advantage to save on the costs of sterilization and water for biohydrogen production from lignocellulosic waste after the pretreatment process with their ability to withstand extreme salt concentrations. This study identifies the dominant hydrogen-producing genera and species among the acclimatized, extremely halotolerant microbial communities taken from two salt-damaged soil locations in Khon Kaen and one location from the salt evaporation pond in Samut Sakhon, Thailand. The microbial communities’ V3–V4 regions of 16srRNA were analyzed using high-throughput amplicon sequencing. A total of 345 operational taxonomic units were obtained and the high-throughput sequencing confirmed that Firmicutes was the dominant phyla of the three communities. Halanaerobium fermentans and Halanaerobacter lacunarum were the dominant hydrogen-producing species of the communities. Spatial proximity was not found to be a determining factor for similarities between these extremely halophilic microbial communities. Through the study of the microbial communities, strategies can be developed to increase biohydrogen molar yield. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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22 pages, 5815 KiB  
Article
Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization
by Katja Karstens, Sergej Trippel and Peter Götz
Fuels 2021, 2(2), 108-129; https://doi.org/10.3390/fuels2020007 - 01 Apr 2021
Cited by 4 | Viewed by 3503
Abstract
The production of butanol, acetone and ethanol by Clostridium acetobutylicum is a biphasic fermentation process. In the first phase the carbohydrate substrate is metabolized to acetic and butyric acid, in the following second phase the product spectrum is shifted towards the economically interesting [...] Read more.
The production of butanol, acetone and ethanol by Clostridium acetobutylicum is a biphasic fermentation process. In the first phase the carbohydrate substrate is metabolized to acetic and butyric acid, in the following second phase the product spectrum is shifted towards the economically interesting solvents. Here we present a cascade of six continuous stirred tank reactors (CCSTR), which allows performing the time dependent metabolic phases of an acetone-butanol-ethanol (ABE) batch fermentation in a spatial domain. Experimental data of steady states under four operating conditions—with variations of the pH in the first bioreactor between 4.3 and 5.6 as well as the total dilution rate between 0.042 h−1 and 0.092 h−1—were used to optimize and validate a corresponding mathematical model. Beyond a residence time distribution representation and substrate, biomass and product kinetics this model also includes the differentiation of cells between the metabolic states. Model simulations predict a final product concentration of 8.2 g butanol L−1 and a productivity of 0.75 g butanol L−1 h−1 in the CCSTR operated at pHbr1 of 4.3 and D = 0.092 h−1, while 31% of the cells are differentiated to the solventogenic state. Aiming at an enrichment of solvent-producing cells, a feedback loop was introduced into the cascade, sending cells from a later state of the process (bioreactor 4) back to an early stage of the process (bioreactor 2). In agreement with the experimental observations, the model accurately predicted an increase in butanol formation rate in bioreactor stages 2 and 3, resulting in an overall butanol productivity of 0.76 g L−1 h−1 for the feedback loop cascade. The here presented CCSTR and the validated model will serve to investigate further ABE fermentation strategies for a controlled metabolic switch. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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Review

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26 pages, 3590 KiB  
Review
The Operating Parameters, Structural Composition, and Fuel Sustainability Aspects of PEM Fuel Cells: A Mini Review
by Muhammad Tawalbeh, Suma Alarab, Amani Al-Othman and Rana Muhammad Nauman Javed
Fuels 2022, 3(3), 449-474; https://doi.org/10.3390/fuels3030028 - 03 Aug 2022
Cited by 23 | Viewed by 8470
Abstract
This mini review discusses the sustainability aspects of various fuels for proton exchange membrane fuel cells (PEMFCs). PEMFCs operate by converting the chemical energy in a fuel into electrical energy. The most crucial parameters in the operation process are the temperature, pressure, relative [...] Read more.
This mini review discusses the sustainability aspects of various fuels for proton exchange membrane fuel cells (PEMFCs). PEMFCs operate by converting the chemical energy in a fuel into electrical energy. The most crucial parameters in the operation process are the temperature, pressure, relative humidity, and air stoichiometry ratio, as presented in this work. The classical structure of a PEMFC consists of a proton exchange membrane, anode electrode, cathode electrode, catalyst layers (CLs), microporous layer (MPLs), gas diffusion layers (GDLs), two bipolar plates (BPs), and gas flow channels (GFCs). The mechanical behavior and the conductivity of the protons are highly dependent on the structure of the MEAs. This review discusses the various fuels and their production paths from sustainable sources. For the fuel production process to be renewable and sustainable, a hydrogen electrolyzer could be powered from solar energy, wind energy, geothermal energy, or hydroelectric energy, to produce hydrogen, which in turn could be fed into the fuel cell. This paper also reviews biomass-based routes for sustainable fuel production. Full article
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
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