Special Issue "Ethanol and Value-Added Co-Products"

A special issue of Fermentation (ISSN 2311-5637).

Deadline for manuscript submissions: 31 January 2019

Special Issue Editors

Guest Editor
Dr. Nhuan Nghiem

Sustainable Biofuels and Co-Products Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA, United States
Website | E-Mail
Interests: fermentation process development; bio-based product; lignocellulosic biomass pretreatment and bioconversion; renewable biofuel and chemical, biological waste treatment; bioremediation
Guest Editor
Prof. Dr. Tae Hyun Kim

Hanyang University, Department Materials Science and Chemical Engineering, Ansan 15588, Gyeonggi-do, Korea
Website 1 | Website 2 | E-Mail
Interests: biofuel; bio-based product; biochemical; pretreatment; bioconversion process integration; biorefinery; bioprocessing

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 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 350 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

Published Papers (4 papers)

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Research

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Open AccessArticle Removal of Bacterial Contamination from Bioethanol Fermentation System Using Membrane Bioreactor
Fermentation 2018, 4(4), 88; https://doi.org/10.3390/fermentation4040088
Received: 25 September 2018 / Revised: 12 October 2018 / Accepted: 16 October 2018 / Published: 18 October 2018
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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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Open AccessArticle Soaking in Aqueous Ammonia (SAA) Pretreatment of Whole Corn Kernels for Cellulosic Ethanol Production from the Fiber Fractions
Fermentation 2018, 4(4), 87; https://doi.org/10.3390/fermentation4040087
Received: 4 September 2018 / Revised: 11 October 2018 / Accepted: 12 October 2018 / Published: 16 October 2018
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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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Graphical abstract

Open AccessFeature PaperArticle Hydrogen-Cycling during Solventogenesis in Clostridium acetobutylicum American Type Culture Collection (ATCC) 824 Requires the [NiFe]-Hydrogenase for Energy Conservation
Fermentation 2018, 4(3), 55; https://doi.org/10.3390/fermentation4030055
Received: 20 June 2018 / Revised: 8 July 2018 / Accepted: 17 July 2018 / Published: 19 July 2018
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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

Jump to: Research

Open AccessReview Seaweed Bioethanol Production: A Process Selection Review on Hydrolysis and Fermentation
Fermentation 2018, 4(4), 99; https://doi.org/10.3390/fermentation4040099
Received: 31 October 2018 / Revised: 20 November 2018 / Accepted: 27 November 2018 / Published: 29 November 2018
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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)

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Techno-economic bottlenecks of fungal pretreatment of lignocellulosic biomass.
Author: Ajay Shah
Abstract: Fungal pretreatment is an alternative biomass pretreatment process that uses rotting fungi to enhance the digestibility of lignocellulosic feedstocks. Fungal pretreatment is performed at low temperature, without added chemicals and no wastewater generation; however, it requires long incubation times and generates lower yields than traditional pretreatments. Because of its simplicity, fungal pretreatment has been described previously as a low-cost process, but no studies have evaluated the techno-economic feasibility of this pretreatment at commercial scale, and the possible bottlenecks of the process. Process modeling and techno-economic analysis of fungal pretreatment of lignocellulosic biomass would allow to identify the main bottlenecks of the fungal pretreatment process to help canalize development resources in order to improve the feasibility of this technology. In this work, we developed a process model of a fungal pretreatment-based cellulosic biorefinery with a 30-million gallons ethanol/year capacity. Experimental data from literature was used as input, accounting for variation in conditions and yields of fungal pretreatment, and different kinds of feedstocks were considered. Additionally, the effect of the variation of process parameters on the production cost were evaluated with sensitivity analysis.

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