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Fermentation
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Ethanol and Value-Added Co-Products
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Ethanol and Value-Added Co-Products

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

Deadline for manuscript submissions: closed (31 January 2019) | Viewed by 68983

Special Issue Editors

Dr. Nhuan Nghiem

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Guest Editor
Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC, USA
Interests: bioprocess engineering; industrial microbiology; biofuels; biobased products; fermentation process development
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Tae Hyun Kim

E-Mail Website1 Website2
Guest Editor
Department Materials Science and Chemical Engineering, Hanyang University, Ansan 15588, Gyeonggi-do, Republic of Korea
Interests: biofuel; bio-based product; biochemical; pretreatment; bioconversion process integration; biorefinery; bioprocessing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Over the years, ethanol has attracted global interest as a renewable and clean liquid fuel. Currently, feedstocks for commercial fuel ethanol production include cereal grains (e.g., corn, wheat, barley, cassava) and sugar crops (e.g., sugarcane, sugar beets, sweet sorghum). Sugarcane and corn are the two feedstocks that have been used most extensively. Despite the commercial success, relentless research efforts have been made to improve the economics of ethanol production through increase of ethanol yield and development of value-added co-products. Some of these efforts have reached commercialization, for example, the extraction of corn oil and the implementation of the D3MAX process for additional ethanol yield from corn fibers at many corn ethanol plants. Production of biogas from the wastes generated in the ethanol production process to provide an energy source for internal uses also has been practiced at commercial scale.

Lignocellulosic biomass recently attracted interest as an alternate potential feedstock for ethanol production mainly because of its availability in large quantities. Research has been performed to develop process technologies for conversion of biomass to ethanol via either the sugar platform or the syngas platform. Several of these processes have been demonstrated at pilot and semi-commercial scales. Industrial chemicals and consumer products that can be made from C5 sugars and lignin have been considered as potential high value-added co-products of cellulosic ethanol.

The goal of this Special Issue is to publish both recent innovative research results, as well as review papers on the production of ethanol and value-added co-products from sugar-based, starch-based and cellulosic biomass feedstocks by biochemical processes. Review and research papers on development of novel enzymes and microbial strains are also of interest. If you would like to contribute a review paper, please contact one of the editors to discuss the topic relevance before submitting the manuscript.

Sincerely,
Dr. Nhuan Nghiem
Prof. Dr. Tae Hyun Kim
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 2100 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

  • ethanol
  • value-added co-products
  • starch-based feedstocks
  • sugar crops
  • lignocellulosic biomass
  • pretreatment
  • enzymatic hydrolysis
  • fermentable sugars
  • gasification
  • syngas fermentation
  • process integration
  • bioreactor
  • cellulose
  • hemicellulose
  • lignin
  • chemical building blocks
  • platform chemicals

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Related Special Issue

Published Papers (7 papers)

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Research

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23 pages, 2645 KiB  
Article
Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass
by Juliana Vasco-Correa and Ajay Shah
Fermentation 2019, 5(2), 30; https://doi.org/10.3390/fermentation5020030 - 29 Mar 2019
Cited by 64 | Viewed by 8668
Abstract
Fungal pretreatment is a biological process that uses rotting fungi to reduce the recalcitrance and enhance the enzymatic digestibility of lignocellulosic feedstocks at low temperature, without added chemicals and wastewater generation. Thus, it has been presumed to be low cost. However, fungal pretreatment [...] Read more.
Fungal pretreatment is a biological process that uses rotting fungi to reduce the recalcitrance and enhance the enzymatic digestibility of lignocellulosic feedstocks at low temperature, without added chemicals and wastewater generation. Thus, it has been presumed to be low cost. However, fungal pretreatment requires longer incubation times and generates lower yields than traditional pretreatments. Thus, this study assesses the techno-economic feasibility of a fungal pretreatment facility for the production of fermentable sugars for a 75,700 m3 (20 million gallons) per year cellulosic bioethanol plant. Four feedstocks were evaluated: perennial grasses, corn stover, agricultural residues other than corn stover, and hardwood. The lowest estimated sugars production cost ($1.6/kg) was obtained from corn stover, and was 4–15 times as much as previous estimates for conventional pretreatment technologies. The facility-related cost was the major contributor (46–51%) to the sugar production cost, mainly because of the requirement of large equipment in high quantities, due to process bottlenecks such as low sugar yields, low feedstock bulk density, long fungal pretreatment times, and sterilization requirements. At the current state of the technology, fungal pretreatment at biorefinery scale does not appear to be economically feasible, and considerable process improvements are still required to achieve product cost targets. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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8 pages, 2030 KiB  
Article
Direct Ethanol Production from Lignocellulosic Materials by Mixed Culture of Wood Rot Fungi Schizophyllum commune, Bjerkandera adusta, and Fomitopsis palustris
by Sakae Horisawa, Akie Inoue and Yuka Yamanaka
Fermentation 2019, 5(1), 21; https://doi.org/10.3390/fermentation5010021 - 15 Feb 2019
Cited by 17 | Viewed by 7578
Abstract
The cost of bioethanol production from lignocellulosic materials is relatively high because the additional processes of delignification and saccharification are required. Consolidated bioprocessing (CBP) simultaneously uses the multiple processes of delignification, saccharification, and fermentation in a single reactor and has the potential to [...] Read more.
The cost of bioethanol production from lignocellulosic materials is relatively high because the additional processes of delignification and saccharification are required. Consolidated bioprocessing (CBP) simultaneously uses the multiple processes of delignification, saccharification, and fermentation in a single reactor and has the potential to solve the problem of cost. Some wood-degrading basidiomycetes have lignin- and cellulose-degrading abilities as well as ethanol fermentation ability. The white rot fungus Schizophyllum commune NBRC 4928 was selected as a strong fermenter from a previous study. The lignin-degrading fungus Bjerkandera adusta and polysaccharide-degrading fungus Fomitopsis palustris were respectively added to S. commune ethanol fermentations to help degrade lignocellulosic materials. Bjerkandera adusta produced more ligninase under aerobic conditions, so a switching aeration condition was adopted. The mixed culture of S. commune and B. adusta promoted direct ethanol production from cedar wood. Fomitopsis palustris produced enzymes that released glucose from both carboxymethylcellulose and microcrystalline cellulose. The mixed culture of S. commune and F. palustris did not enhance ethanol production from cedar. The combination of S. commune and cellulase significantly increased the rate of ethanol production. The results suggest that CBP for ethanol production from cellulosic material can be achieved by using multiple fungi in one reactor. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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9 pages, 1147 KiB  
Article
Optimization of an Industrial Medium from Molasses for Bioethanol Production Using the Taguchi Statistical Experimental-Design Method
by Farshad Darvishi and Nooshin Abolhasan Moghaddami
Fermentation 2019, 5(1), 14; https://doi.org/10.3390/fermentation5010014 - 26 Jan 2019
Cited by 28 | Viewed by 10254
Abstract
The production of bioethanol as a clean liquid fuel in a cost-effective way is highly desired by global energetics. Sugar beet molasses is a renewable and cheap substrate for the production of biotechnological products. Therefore, the aim of the current study was the [...] Read more.
The production of bioethanol as a clean liquid fuel in a cost-effective way is highly desired by global energetics. Sugar beet molasses is a renewable and cheap substrate for the production of biotechnological products. Therefore, the aim of the current study was the optimization of an industrial medium from molasses for bioethanol production using the Taguchi statistical experimental-design method. First, the growth rate of yeast cells and the amount of ethanol produced by the Saccharomyces cerevisiae strain sahand 101 were investigated in aerobic and aerobic–anaerobic conditions. The yeast strain produced 8% (v/v) bioethanol in a medium containing molasses with 18% Brix in aerobic–anaerobic conditions. The main factors of the medium, including molasses, ammonium sulfate, urea, and pH, were optimized for the increase of bioethanol production by the Taguchi method. Bioethanol production reached 10% (v/v) after optimization of the medium in flask culture. The yeast strain produced 11% (v/v) bioethanol in the bioreactor culture containing the optimized medium, which is an acceptable amount of bioethanol produced from molasses at the industrial scale. The results showed that the Taguchi method is an effective method for the design of experiments aiming to optimize the medium for bioethanol production by reducing the number of experiments and time. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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18 pages, 3261 KiB  
Article
Removal of Bacterial Contamination from Bioethanol Fermentation System Using Membrane Bioreactor
by Amir Mahboubi, Beray Cayli, Gülru Bulkan, Wim Doyen, Heleen De Wever and Mohammad J. Taherzadeh
Fermentation 2018, 4(4), 88; https://doi.org/10.3390/fermentation4040088 - 18 Oct 2018
Cited by 11 | Viewed by 10905
Abstract
A major issue hindering efficient industrial ethanol fermentation from sugar-based feedstock is excessive unwanted bacterial contamination. In industrial scale fermentation, reaching complete sterility is costly, laborious, and difficult to sustain in long-term operation. A physical selective separation of a co-culture of Saccharomyces cerevisiae [...] Read more.
A major issue hindering efficient industrial ethanol fermentation from sugar-based feedstock is excessive unwanted bacterial contamination. In industrial scale fermentation, reaching complete sterility is costly, laborious, and difficult to sustain in long-term operation. A physical selective separation of a co-culture of Saccharomyces cerevisiae and an Enterobacter cloacae complex from a buffer solution and fermentation media at dilution rates of 0.1–1 1/h were examined using an immersed membrane bioreactor (iMBR). The effect of the presence of yeast, inoculum size, membrane pore size, and surface area, backwashing and dilution rate on bacteria removal were assessed by evaluating changes in the filtration conditions, medium turbidity, and concentration of compounds and cell biomass. The results showed that using the iMBR with dilution rate of 0.5 1/h results in successful removal of 93% of contaminating bacteria in the single culture and nearly complete bacteria decontamination in yeast-bacteria co-culture. During continuous fermentation, application of lower permeate fluxes provided a stable filtration of the mixed culture with enhanced bacteria washout. This physical selective separation of bacteria from yeast can enhance final ethanol quality and yields, process profitability, yeast metabolic activity, and decrease downstream processing costs. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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10 pages, 1181 KiB  
Article
Soaking in Aqueous Ammonia (SAA) Pretreatment of Whole Corn Kernels for Cellulosic Ethanol Production from the Fiber Fractions
by Katherine L. Norvell and Nhuan P. Nghiem
Fermentation 2018, 4(4), 87; https://doi.org/10.3390/fermentation4040087 - 16 Oct 2018
Cited by 5 | Viewed by 6592
Abstract
Corn fiber is a co-product of commercial ethanol dry-grind plants, which is processed into distillers dried grains with solubles (DDGS) and used as animal feed, yet it holds high potential to be used as feedstock for additional ethanol production. Due to the tight [...] Read more.
Corn fiber is a co-product of commercial ethanol dry-grind plants, which is processed into distillers dried grains with solubles (DDGS) and used as animal feed, yet it holds high potential to be used as feedstock for additional ethanol production. Due to the tight structural make-up of corn fiber, a pretreatment step is necessary to make the cellulose and hemicellulose polymers in the solid fibrous matrix more accessible to the hydrolytic enzymes. A pretreatment process was developed in which whole corn kernels were soaked in aqueous solutions of 2.5, 5.0, 7.5, and 10.0 wt% ammonia at 105 °C for 24 h. The pretreated corn then was subjected to a conventional mashing procedure and subsequent ethanol fermentation using a commercial strain of natural Saccharomyces cerevisiae with addition of a commercial cellulase. Pretreatment of the corn with 7.5 wt% ammonia solution plus cellulase addition gave the highest ethanol production, which improved the yield in fermentation using 25 wt% solid from 334 g ethanol/kg corn obtained in the control (no pretreatment and no cellulase addition) to 379 g ethanol/kg corn (a 14% increase). The process developed can potentially be implemented in existing dry-grind ethanol facilities as a “bolt-on” process for additional ethanol production from corn fiber, and this additional ethanol can then qualify as “cellulosic ethanol” by the Environmental Protection Agency’s (EPA’s) Renewable Fuels Standard and thereby receive RINs (Renewable Identification Numbers). Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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16 pages, 1835 KiB  
Article
Hydrogen-Cycling during Solventogenesis in Clostridium acetobutylicum American Type Culture Collection (ATCC) 824 Requires the [NiFe]-Hydrogenase for Energy Conservation
by Katherine L. Germane, Sanchao Liu, Elliot S. Gerlach, Alice M. Savage, Rebecca L. Renberg, Theresah N. K. Zu, Hong Dong, Scott D. Walck, Matthew D. Servinsky and Christian J. Sund
Fermentation 2018, 4(3), 55; https://doi.org/10.3390/fermentation4030055 - 19 Jul 2018
Cited by 5 | Viewed by 5193
Abstract
Clostridium acetobutylicum has traditionally been used for production of acetone, butanol, and ethanol (ABE). Butanol is a commodity chemical due in part to its suitability as a biofuel; however, the current yield of this product from biological systems is not economically feasible as [...] Read more.
Clostridium acetobutylicum has traditionally been used for production of acetone, butanol, and ethanol (ABE). Butanol is a commodity chemical due in part to its suitability as a biofuel; however, the current yield of this product from biological systems is not economically feasible as an alternative fuel source. Understanding solvent phase physiology, solvent tolerance, and their genetic underpinning is key for future strain optimization of the bacterium. This study shows the importance of a [NiFe]-hydrogenase in solvent phase physiology. C. acetobutylicum genes ca_c0810 and ca_c0811, annotated as a HypF and HypD maturation factor, were found to be required for [NiFe]-hydrogenase activity. They were shown to be part of a polycistronic operon with other hyp genes. Hydrogenase activity assays of the ΔhypF/hypD mutant showed an almost complete inactivation of the [NiFe]-hydrogenase. Metabolic studies comparing ΔhypF/hypD and wild type (WT) strains in planktonic and sessile conditions indicated the hydrogenase was important for solvent phase metabolism. For the mutant, reabsorption of acetate and butyrate was inhibited during solventogenesis in planktonic cultures, and less ABE was produced. During sessile growth, the ΔhypF/hypD mutant had higher initial acetone: butanol ratios, which is consistent with the inability to obtain reduced cofactors via H2 uptake. In sessile conditions, the ΔhypF/hypD mutant was inhibited in early solventogenesis, but it appeared to remodel its metabolism and produced mainly butanol in late solventogenesis without the uptake of acids. Energy filtered transmission electron microscopy (EFTEM) mapped Pd(II) reduction via [NiFe]-hydrogenase induced H2 oxidation at the extracelluar side of the membrane on WT cells. A decrease of Pd(0) deposits on ΔhypF/hypD comparatively to WT indicates that the [NiFe]-hydrogenase contributed to the Pd(II) reduction. Calculations of reaction potentials during acidogenesis and solventogenesis predict the [NiFe]-hydrogenase can couple NAD+ reduction with membrane transport of electrons. Extracellular oxidation of H2 combined with the potential for electron transport across the membrane indicate that the [NiFe}-hydrogenase contributes to proton motive force maintenance via hydrogen cycling. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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Review

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18 pages, 300 KiB  
Review
Seaweed Bioethanol Production: A Process Selection Review on Hydrolysis and Fermentation
by Felix Offei, Moses Mensah, Anders Thygesen and Francis Kemausuor
Fermentation 2018, 4(4), 99; https://doi.org/10.3390/fermentation4040099 - 29 Nov 2018
Cited by 85 | Viewed by 17231
Abstract
The rapid depletion and environmental concerns associated with the use of fossil fuels has led to extensive development of biofuels such as bioethanol from seaweeds. The long-term prospect of seaweed bioethanol production however, depends on the selection of processes in the hydrolysis and [...] Read more.
The rapid depletion and environmental concerns associated with the use of fossil fuels has led to extensive development of biofuels such as bioethanol from seaweeds. The long-term prospect of seaweed bioethanol production however, depends on the selection of processes in the hydrolysis and fermentation stages due to their limiting effect on ethanol yield. This review explored the factors influencing the hydrolysis and fermentation stages of seaweed bioethanol production with emphasis on process efficiency and sustainable application. Seaweed carbohydrate contents which are most critical for ethanol production substrate selection were 52 ± 6%, 55 ± 12% and 57 ± 13% for green, brown and red seaweeds, respectively. Inhibitor formation and polysaccharide selectivity were found to be the major bottlenecks influencing the efficiency of dilute acid and enzymatic hydrolysis, respectively. Current enzyme preparations used, were developed for starch-based and lignocellulosic biomass but not seaweeds, which differs in polysaccharide composition and structure. Also, the identification of fermenting organisms capable of converting the heterogeneous monomeric sugars in seaweeds is the major factor limiting ethanol yield during the fermentation stage and not the SHF or SSF pathway selection. This has resulted in variations in bioethanol yields, ranging from 0.04 g/g DM to 0.43 g/g DM. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products)
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