Ethanol and Value-Added Co-Products 2.0

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

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 38206

Special Issue Editors

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
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 its commercial success, relentless research efforts have been made to improve the economics of ethanol production through the 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 semicommercial 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 the 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.

Dr. Nhuan Nghiem
Prof. Dr. Tae Hyun Kim
Guest Editors

Manuscript Submission Information

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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.

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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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Published Papers (7 papers)

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Research

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15 pages, 1542 KiB  
Article
Abatement of Inhibitors in Recycled Process Water from Biomass Fermentations Relieves Inhibition of a Saccharomyces cerevisiae Pentose Phosphate Pathway Mutant
Fermentation 2020, 6(4), 107; https://doi.org/10.3390/fermentation6040107 - 10 Nov 2020
Viewed by 2182
Abstract
Understanding the nature of fermentation inhibition in biomass hydrolysates and recycled fermentation process water is important for conversion of biomass to fuels and chemicals. This study used three mutants disrupted in genes important for tolerance to either oxidative stress, salinity, or osmolarity to [...] Read more.
Understanding the nature of fermentation inhibition in biomass hydrolysates and recycled fermentation process water is important for conversion of biomass to fuels and chemicals. This study used three mutants disrupted in genes important for tolerance to either oxidative stress, salinity, or osmolarity to ferment biomass hydrolysates in a xylose-fermenting Saccharomyces cerevisiae background. The S. cerevisiaeZWF1 mutant with heightened sensitivity to fermentation inhibitors was unable to ferment corn stover dilute-acid hydrolysate without conditioning of hydrolysate using a fungal strain, Coniochaeta ligniaria, to consume inhibitors. Growth of two other strains, a salt-sensitive HAL4 mutant and a GPD1 mutant sensitive to osmotic stress, was not negatively affected in hydrolysate compared to the parent xylose-metabolizing strain. In recycled fermentation process water, inhibition of the ZWF1 mutant could again be remediated by biological abatement, and no effect on growth was observed for any of the mutants compared to the parent strain. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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17 pages, 3225 KiB  
Article
Techno-Economic Analysis of Bioethanol Plant By-Product Valorization: Exploring Market Opportunities with Protein-Rich Fungal Biomass Production
Fermentation 2020, 6(4), 99; https://doi.org/10.3390/fermentation6040099 - 21 Oct 2020
Cited by 9 | Viewed by 4690
Abstract
The feasibility of dry-grind bioethanol plants is extremely dependent on selling prices of ethanol and by-products, known as Dried distillers grains with solubles (DDGS), and sold as animal feed. Increasing the amount and quality of the by-products can widen potential feed and food [...] Read more.
The feasibility of dry-grind bioethanol plants is extremely dependent on selling prices of ethanol and by-products, known as Dried distillers grains with solubles (DDGS), and sold as animal feed. Increasing the amount and quality of the by-products can widen potential feed and food markets and improve the process economy and robustness to price fluctuations of ethanol and grain. In this study, the techno-economic analysis of a bioethanol plant was investigated. Integration of edible filamentous fungi into the process leading to the conversion of sidestreams into ethanol and protein-rich fungal biomass for food and feed applications was considered, and its impact was investigated. Sensitivity analysis considered variations on process capacity, on the price of grain and ethanol, and on the price of fungal biomass considering its use for various animal feed (e.g., pig and fish) and human food markets. Selling the fungal biomass in the human food market resulted in 5.56 times higher NPV (net present value) than the base case bioethanol plant after 20 years. Integration of a low-performing strain towards ethanol, followed by the usage of the fungal biomass in the food sector, was found to be the most resistant scenario to the low ethanol selling price and increasing grain price. This study showed that the competitiveness of ethanol plants in the fuel market could be reinforced while meeting the increasing demand for protein sources. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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11 pages, 1318 KiB  
Article
Global View of Biofuel Butanol and Economics of Its Production by Fermentation from Sweet Sorghum Bagasse, Food Waste, and Yellow Top Presscake: Application of Novel Technologies
Fermentation 2020, 6(2), 58; https://doi.org/10.3390/fermentation6020058 - 03 Jun 2020
Cited by 23 | Viewed by 4958
Abstract
Worldwide, there are various feedstocks such as straws, corn stover, sugarcane bagasse, sweet sorghum bagasse (SSB), grasses, leaves, whey permeate, household organic waste, and food waste (FW) that can be converted to valuable biofuels such as butanol. For the present studies, an economic [...] Read more.
Worldwide, there are various feedstocks such as straws, corn stover, sugarcane bagasse, sweet sorghum bagasse (SSB), grasses, leaves, whey permeate, household organic waste, and food waste (FW) that can be converted to valuable biofuels such as butanol. For the present studies, an economic analysis was performed to compare butanol production from three feedstocks (SSB; FW; and yellow top presscake, YTP or YT) using a standard process and an advanced integrated process design. The total plant capacity was set at 170,000–171,000 metric tons of total acetone butanol ethanol (ABE) per year (99,300 tons of just butanol per year). Butanol production from SSB typically requires pretreatment, separate hydrolysis, fermentation, and product recovery (SHFR). An advanced process was developed in which the last three steps were combined into a single unit operation for simultaneous saccharification, fermentation, and recovery (SSFR). For the SHFR and SSFR plants, the total capital investments were estimated as $213.72 × 106 and $198.16 × 106, respectively. It was further estimated that the minimum butanol selling price (using SSB as a feedstock) for the two processes were $1.14/kg and $1.05/kg. Therefore, SSFR lowered the production cost markedly compared to that of the base case. Butanol made using FW had an estimated minimum selling price of only $0.42/kg. This low selling price is because the FW to butanol process does not require pretreatment, hydrolysis, and cellulolytic enzymes. For this plant, the total capital investment was projected to be $107.26 × 106. The butanol selling price using YTP as a feedstock was at $0.73/kg and $0.79/kg with total capital investments for SSFR and SHFR of $122.58 × 106 and $132.21 × 106, respectively. In the Results and Discussion section, the availability of different feedstocks in various countries such as Brazil, the European Union, New Zealand, Denmark, and the United States are discussed. Additionally, the use of various microbial strains and product recovery technologies are also discussed. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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15 pages, 2650 KiB  
Article
High Gravity Fermentation of Sugarcane Bagasse Hydrolysate by Saccharomyces pastorianus to Produce Economically Distillable Ethanol Concentrations: Necessity of Medium Components Examined
Fermentation 2020, 6(1), 8; https://doi.org/10.3390/fermentation6010008 - 08 Jan 2020
Cited by 5 | Viewed by 6031
Abstract
A major economic obstacle in lignocellulosic ethanol production is the low sugar concentrations in the hydrolysate and subsequent fermentation to economically distillable ethanol concentrations. We have previously demonstrated a two-stage fermentation process that recycles xylose with xylose isomerase to increase ethanol productivity, where [...] Read more.
A major economic obstacle in lignocellulosic ethanol production is the low sugar concentrations in the hydrolysate and subsequent fermentation to economically distillable ethanol concentrations. We have previously demonstrated a two-stage fermentation process that recycles xylose with xylose isomerase to increase ethanol productivity, where the low sugar concentrations in the hydrolysate limit the final ethanol concentrations. In this study, three approaches are combined to increase ethanol concentrations. First, the medium-additive requirements were investigated to reduce ethanol dilution. Second, methods to increase the sugar concentrations in the sugarcane bagasse hydrolysate were undertaken. Third, the two-stage fermentation process was recharacterized with high gravity hydrolysate. It was determined that phosphate and magnesium sulfate are essential to the ethanol fermentation. Additionally, the Escherichia coli extract and xylose isomerase additions were shown to significantly increase ethanol productivity. Finally, the fermentation on hydrolysate had only slightly lower productivity than the reagent-grade sugar fermentation; however, both fermentations had similar final ethanol concentrations. The present work demonstrates the capability to produce ethanol from high gravity sugarcane bagasse hydrolysate using Saccharomyces pastorianus with low yeast inoculum in minimal medium. Moreover, ethanol productivities were on par with pilot-scale commercial starch-based facilities, even when the yeast biomass production stage was included. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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17 pages, 2899 KiB  
Article
Xylose-Enriched Ethanol Fermentation Stillage from Sweet Sorghum for Xylitol and Astaxanthin Production
Fermentation 2019, 5(4), 84; https://doi.org/10.3390/fermentation5040084 - 23 Sep 2019
Cited by 11 | Viewed by 4280
Abstract
Developing integrated biorefineries requires the generation of high-value co-products produced alongside cellulosic ethanol. Most industrial yeast strains produce ethanol at high titers, but the small profit margins for generating ethanol require that additional high-value chemicals be generated to improve revenue. The aim of [...] Read more.
Developing integrated biorefineries requires the generation of high-value co-products produced alongside cellulosic ethanol. Most industrial yeast strains produce ethanol at high titers, but the small profit margins for generating ethanol require that additional high-value chemicals be generated to improve revenue. The aim of this research was to boost xylose utilization and conversion to high-value co-products that can be generated in an integrated biorefinery. Pretreated sweet sorghum bagasse (SSB) was hydrolyzed in sweet sorghum juice (SSJ) followed by ethanol fermentation. Ethanol was removed from the fermentation broth by evaporation to generate a stillage media enriched in xylose. Candida mogii NRRL Y-17032 could easily grow in non-detoxified stillage media, but a high xylitol yield of 0.55 g xylitol/g xylose consumed was achieved after recovered cells were resuspended in synthetic media containing supplemented xylose. Phaffia rhodozyma ATCC 74219 could be cultivated in non-detoxified stillage media, but astaxanthin generation was increased 4-fold (from 17.5 to 71.7 mg/L) in detoxified media. Future processing strategies to boost product output should focus on a two-step process where the stillage media is used as the growth stage, and a synthetic media for the production stage utilizing xylose generated from SSB through selective hemicellulase enzymes. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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Review

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17 pages, 8546 KiB  
Review
Recent Advancements in Biological Conversion of Industrial Hemp for Biofuel and Value-Added Products
Fermentation 2021, 7(1), 6; https://doi.org/10.3390/fermentation7010006 - 05 Jan 2021
Cited by 23 | Viewed by 9988
Abstract
Sustainable, economically feasible, and green resources for energy and chemical products have people’s attention due to global energy demand and environmental issues. Last several decades, diverse lignocellulosic biomass has been studied for the production of biofuels and biochemicals. Industrial hemp has great market [...] Read more.
Sustainable, economically feasible, and green resources for energy and chemical products have people’s attention due to global energy demand and environmental issues. Last several decades, diverse lignocellulosic biomass has been studied for the production of biofuels and biochemicals. Industrial hemp has great market potential with its versatile applications. With the increase of the hemp-related markets with hemp seed, hemp oil, and fiber, the importance of hemp biomass utilization has also been emphasized in recent studies. Biological conversions of industrial hemp into bioethanol and other biochemicals have been introduced to address the aforementioned energy and environmental challenges. Its high cellulose content and the increased production because of the demand for cannabidiol oil and hempseed products make it a promising future bioenergy and biochemical source. Effective valorization of the underutilized hemp biomass can also improve the cost-competitiveness of hemp products. This manuscript reviews recent biological conversion strategies for industrial hemp and its characteristics. Current understanding of the industrial hemp properties and applied conversion technologies are briefly summarized. In addition, challenges and future perspectives of the biological conversion with industrial hemp are discussed. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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19 pages, 334 KiB  
Review
Kluyveromyces marxianus: Current State of Omics Studies, Strain Improvement Strategy and Potential Industrial Implementation
Fermentation 2020, 6(4), 124; https://doi.org/10.3390/fermentation6040124 - 11 Dec 2020
Cited by 17 | Viewed by 4762
Abstract
Bioethanol is considered an excellent alternative to fossil fuels, since it importantly contributes to the reduced consumption of crude oil, and to the alleviation of environmental pollution. Up to now, the baker yeast Saccharomyces cerevisiae is the most common eukaryotic microorganism used in [...] Read more.
Bioethanol is considered an excellent alternative to fossil fuels, since it importantly contributes to the reduced consumption of crude oil, and to the alleviation of environmental pollution. Up to now, the baker yeast Saccharomyces cerevisiae is the most common eukaryotic microorganism used in ethanol production. The inability of S. cerevisiae to grow on pentoses, however, hinders its effective growth on plant biomass hydrolysates, which contain large amounts of C5 and C12 sugars. The industrial-scale bioprocessing requires high temperature bioreactors, diverse carbon sources, and the high titer production of volatile compounds. These criteria indicate that the search for alternative microbes possessing useful traits that meet the required standards of bioethanol production is necessary. Compared to other yeasts, Kluyveromyces marxianus has several advantages over others, e.g., it could grow on a broad spectrum of substrates (C5, C6 and C12 sugars); tolerate high temperature, toxins, and a wide range of pH values; and produce volatile short-chain ester. K. marxianus also shows a high ethanol production rate at high temperature and is a Crabtree-negative species. These attributes make K. marxianus promising as an industrial host for the biosynthesis of biofuels and other valuable chemicals. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-Products 2.0)
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