Ethanol and Value-Added Co-products 3.0

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

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 105319

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Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC, USA
Interests: bioprocess engineering; industrial microbiology; biofuels; biobased products; fermentation process development
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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 clean and renewable liquid fuel. Recently, ethanol has attracted additional interest as a potential renewable feedstock for the production of drop-in biofuels, which can be blended directly with petroleum-based liquid fuels in the existing infrastructure, via several newly developed catalytic systems and processes.

Currently, feedstocks for commercial fuel ethanol production include cereal grains (corn, sorghum, wheat, barley), roots (cassava) and sugar crops (sugarcane and sugar beets). 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 in ethanol yield and the 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. The production of biogas from waste generated in the ethanol production process to provide an energy source for internal uses has also been practiced at commercial scale.

Lignocellulosic biomass has 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 the 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. In the processes that use the sugar platform, both glucose and xylose can be used for ethanol production. The use of glucose as a substrate for ethanol fermentation, however, is still preferred, because its conversion can be performed with the non-recombinant and commercially proven Saccharomyces cerevisiae yeast. 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.

Ethanol is a bulk chemical with a rather small profit margin; therefore, the development and sales of value-added co-products are of very significant economic importance for commercial sugar-based, starch-based, and lignocellulosic ethanol technologies.

The goal of this Special Issue is to publish 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. Technologies and processes developed for feedstocks that have not been used commercially are of particular interest. 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

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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 (11 papers)

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Research

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10 pages, 1624 KiB  
Article
Corn Stover Pretreatment with Na2CO3 Solution from Absorption of Recovered CO2
by Valerie García-Negrón and Matthew J. Toht
Fermentation 2022, 8(11), 600; https://doi.org/10.3390/fermentation8110600 - 3 Nov 2022
Cited by 3 | Viewed by 1857
Abstract
Renewable resources such as lignocellulosic biomass are effective at producing fermentable sugars during enzymatic hydrolysis when pretreated. Optimizing pretreatment methods for delignification while maintaining sustainability and low processing costs requires innovative strategies such as reusing greenhouse gas emissions for materials processing. Corn stover, [...] Read more.
Renewable resources such as lignocellulosic biomass are effective at producing fermentable sugars during enzymatic hydrolysis when pretreated. Optimizing pretreatment methods for delignification while maintaining sustainability and low processing costs requires innovative strategies such as reusing greenhouse gas emissions for materials processing. Corn stover, an agricultural waste residue, was pretreated with 2.2 M Na2CO3 produced from CO2 captured via absorption in a 5 M NaOH solution. Composition analysis of the pretreated corn stover exhibited higher cellulose content (40.96%) and less lignin (16.50%) than the untreated biomass. Changes in the chemical structures are visible in the FTIR-ATR spectra, particularly in the cellulose and lignin-related absorption bands. The sugar release from hydrolysis was evaluated at different time intervals and by varying two enzyme ratios of CTec2-to-HTec2 (2:1 and 3:1). Enzymatic hydrolysis produced higher and more stable glucose yields for the pretreated biomass, surpassing 90% after 24 h using the 3:1 enzyme ratio. Sugar concentrations notably increased after pretreatment and even more when using the cellulase-rich enzyme solution. The maximum glucose, xylose, and arabinose recovered were 44, 19, and 2.3 g L−1. These results demonstrate the viability of capturing CO2 and converting it into an efficient Na2CO3 pretreatment for corn stover biomass. Additional processing optimizations depend on the combination of physicochemical parameters selected. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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13 pages, 1596 KiB  
Article
Butyric Acid Production by Fermentation: Employing Potential of the Novel Clostridium tyrobutyricum Strain NRRL 67062
by Nasib Qureshi, Siqing Liu and Badal C. Saha
Fermentation 2022, 8(10), 491; https://doi.org/10.3390/fermentation8100491 - 28 Sep 2022
Cited by 3 | Viewed by 3099
Abstract
In this study, the ability of a novel strain of Clostridium tyrobutyricum NRRL 67062 to produce butyric acid during glucose fermentation was evaluated. The strain was evaluated for substrate and product inhibition in batch experiments using anaerobic tubes. To characterize glucose inhibition, initial [...] Read more.
In this study, the ability of a novel strain of Clostridium tyrobutyricum NRRL 67062 to produce butyric acid during glucose fermentation was evaluated. The strain was evaluated for substrate and product inhibition in batch experiments using anaerobic tubes. To characterize glucose inhibition, initial glucose concentrations ranging from 60 to 250 g L−1 were used, and it was demonstrated that a glucose concentration of 250 g L−1 exerted strong inhibition on cell growth and fermentation. To evaluate butyric acid inhibition, the culture was challenged with 5–50 g L−1 of butyric acid at an initial pH of 6.5. These experiments were performed without pH control. When challenged with a butyric acid concentration of 50 g L−1, cell growth was slow; however, it produced 8.25 g L−1 of butyric acid. This suggested that the butyric acid tolerance of the culture was 58 g L−1. In a scaled-up batch experiment, which was performed in a 2.5 L fermentor with an initial glucose concentration of 100 g L−1, the pH was controlled at 6.5. In this experiment, the strain produced 57.86 g L−1 of butyric acid and 12.88 g L−1 of acetic acid, thus producing 70.74 g L−1 of total acids with a productivity of 0.69 g·L−1·h−1. A concentration of 70.74 g L−1 of acids equates to a yield of 0.71 g of acid per g consumed glucose. The maximum cell concentration was 3.80 g L−1, which may have been the reason for high productivity in the batch culture. Finally, corn steep liquor (CSL; a commercial nutrient solution) provided greater growth and acid production than the refined medium. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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11 pages, 941 KiB  
Article
Effectiveness of Tannin Removal by Alkaline Pretreatment on Sorghum Ethanol Production
by Franco Foglia, Caye Drapcho and John Nghiem
Fermentation 2022, 8(6), 274; https://doi.org/10.3390/fermentation8060274 - 13 Jun 2022
Cited by 3 | Viewed by 1852
Abstract
Sorghum has been proposed as a complement or replacement for corn in ethanol production. One difference between sorghum and corn is the presence of tannins, which may affect enzymatic activity. High-tannin sorghum hybrid XM217 was used to analyze the effect of tannin removal [...] Read more.
Sorghum has been proposed as a complement or replacement for corn in ethanol production. One difference between sorghum and corn is the presence of tannins, which may affect enzymatic activity. High-tannin sorghum hybrid XM217 was used to analyze the effect of tannin removal by the alkaline pretreatment of sorghum for ethanol production. A laboratory-scale dry-milling process was used on treated sorghum/corn blends to generate mash that was fermented by Saccharomyces cerevisiae and then compared to a 100% untreated sorghum control. Cellulase was added to a similar set of mash to determine the feasibility of the tannin-removal treatment as a pretreatment method for cellulosic ethanol production. Theoretical ethanol yield increased from 68.2 ± 1.5% to 78.5 ± 2.5% for alkaline-pretreated sorghum vs. untreated sorghum, with a corresponding increase in mean ethanol concentrations from 8.02 ± 0.15 to 9.39 ± 0.26% w/v. The average theoretical ethanol yield increased from 69.8 ± 1.7% to 94.6 ± 1.9% when using cellulase with untreated and treated sorghum. The use of alkaline tannin removal resulted in a significant increase in the theoretical ethanol yield obtained when using 100% sorghum, when compared to the theoretical ethanol yield obtained when using 100% corn. The combination of cellulase and alkaline tannin removal improved the yield of ethanol in all cases compared to the experiments without cellulase. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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14 pages, 4086 KiB  
Article
Mathematical Modelling of Bioethanol Production from Raw Sugar Beet Cossettes in a Horizontal Rotating Tubular Bioreactor
by Mladen Pavlečić, Mario Novak, Antonija Trontel, Nenad Marđetko, Marina Grubišić, Blanka Didak Ljubas, Vlatka Petravić Tominac, Rozelindra Čož Rakovac and Božidar Šantek
Fermentation 2022, 8(1), 13; https://doi.org/10.3390/fermentation8010013 - 30 Dec 2021
Cited by 1 | Viewed by 2583
Abstract
Alternative to the use of fossil fuels are biofuels (e.g., bioethanol, biodiesel and biogas), which are more environmentally friendly and which can be produced from different renewable resources. In this investigation, bioethanol production from raw sugar beet cossettes (semi-solid substrate) by yeast Saccharomyces [...] Read more.
Alternative to the use of fossil fuels are biofuels (e.g., bioethanol, biodiesel and biogas), which are more environmentally friendly and which can be produced from different renewable resources. In this investigation, bioethanol production from raw sugar beet cossettes (semi-solid substrate) by yeast Saccharomyces cerevisiae in a horizontal rotating tubular bioreactor (HRTB) was studied. Obtained results show that HRTB rotation mode (constant or interval) and rotation speed have considerable impact on the efficiency of bioethanol production in the HRTB. The main goal of this research was to develop a non-structural mathematical model of bioethanol production from raw sugar beet cossettes in the HRTB. The established mathematical model of bioethanol production in the HRTB describes substrate utilization and product formation (glycerol, ethanol and acetate) and presumes negative impact of high substrate concentration on the working microorganism (substrate inhibition) by using Andrews inhibition kinetics. All simulations of bioethanol production in the HRTB were performed by using Berkeley Madonna software, version 8.3.14 (Berkeley Madonna, Berkeley, CA, USA). The established non-structural bioprocess model describes relatively well the bioethanol production from raw sugar beet cossettes in the HRTB. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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13 pages, 3210 KiB  
Article
Bioleaching of Sorghum Straw in Bioreactors for Biomass Cleaning
by Ning Zhang, Terry Walker, Bryan Jenkins, Stanley Anderson and Yi Zheng
Fermentation 2021, 7(4), 270; https://doi.org/10.3390/fermentation7040270 - 19 Nov 2021
Cited by 2 | Viewed by 1737
Abstract
Pretreatments are often needed for lignocellulosic biomass feedstocks before either thermochemical or biochemical conversion processes. Our previous research has demonstrated the potential of bioleaching, with its superior capability of removing certain inorganic compounds compared to water leaching, to improve biomass quality for thermochemical [...] Read more.
Pretreatments are often needed for lignocellulosic biomass feedstocks before either thermochemical or biochemical conversion processes. Our previous research has demonstrated the potential of bioleaching, with its superior capability of removing certain inorganic compounds compared to water leaching, to improve biomass quality for thermochemical conversion in biofuel production. In this study, the bioleaching process was scaled up from 250 mL beakers to be carried out in custom-designed 2.5 L bioreactors. The fungus Aspergillus niger was used in the bioreactors for leaching sorghum straw biomass with an initial ash content of 6.0%. The effects of three operating parameters on leaching efficiency (i.e., residual ash content) were extensively studied, including the fungal mass added to each reactor, leaching time, and glucose concentration in the starting liquid phase. Response surface methodology (RSM) was used for the experiment design. The results showed that the average residual ash content of the sorghum feedstock after bioleaching was significantly lower (3.63 ± 0.19%) than that of the ash content (4.72 ± 0.13%) after water leaching (p < 0.00001). Among the three parameters, glucose concentration in the starting liquid phase had the most significant effect on leaching effectiveness (p = 0.0079). Based on this outcome, subsequent bioleaching experiments yielded reductions in residual ash content to as low as 2.73%. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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16 pages, 2516 KiB  
Article
Pretreatment of Corn Stover Using an Extremely Low-Liquid Ammonia (ELLA) Method for the Effective Utilization of Sugars in Simultaneous Saccharification and Fermentation (SSF) of Ethanol
by Tin Diep Trung Le, Vi Phuong Nguyen Truong, My Thi Tra Ngo, Tae Hyun Kim and Kyeong Keun Oh
Fermentation 2021, 7(3), 191; https://doi.org/10.3390/fermentation7030191 - 14 Sep 2021
Cited by 8 | Viewed by 2680
Abstract
Extremely low-liquid ammonia (ELLA) pretreatment using aqueous ammonia was investigated in order to enhance the enzymatic saccharification of corn stover and subsequent ethanol production. In this study, corn stover was treated with an aqueous ammonia solution at different ammonia loading rates (0.1, 0.2, [...] Read more.
Extremely low-liquid ammonia (ELLA) pretreatment using aqueous ammonia was investigated in order to enhance the enzymatic saccharification of corn stover and subsequent ethanol production. In this study, corn stover was treated with an aqueous ammonia solution at different ammonia loading rates (0.1, 0.2, and 0.3 g NH3/g biomass) and various liquid-to-solid (L/S) ratios (0.55, 1.12, and 2.5). The ELLA pretreatment was conducted at elevated temperatures (90–150 °C) for an extended period (24–120 h). Thereafter, the pretreated material was saccharified by enzyme digestion and subjected to simultaneous saccharification and fermentation (SSF) tests. The effects of key parameters on both glucan digestibility and xylan digestibility were analyzed using analysis of variance (ANOVA). Under optimal pretreatment conditions (L/S = 2.5, 0.1 g-NH3/g-biomass, 150 °C), 81.2% glucan digestibility and 61.1% xylan digestibility were achieved. The highest ethanol yield achieved on the SSF tests was 85.4%. The ethanol concentration was 14.5 g/L at 96 h (pretreatment conditions: liquid-to-solid ratio (L/S) = 2.5, 0.1 g-NH3/g-biomass, 150 °C, 24 h. SSF conditions: microorganism Saccharomyces cerevisiae (D5A), 15 FPU/g-glucan, CTech2, 3% w/v glucan, 37 °C, 150 rpm). Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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17 pages, 2487 KiB  
Article
Highly Efficient 2,3-Butanediol Production by Bacillus licheniformis via Complex Optimization of Nutritional and Technological Parameters
by Lidia Tsigoriyna, Dimitar Ganchev, Penka Petrova and Kaloyan Petrov
Fermentation 2021, 7(3), 118; https://doi.org/10.3390/fermentation7030118 - 16 Jul 2021
Cited by 17 | Viewed by 2905
Abstract
2,3-Butanediol (2,3-BD) is a reagent with remarkable commercial use as a platform chemical in numerous industries. The present study aims to determine the capabilities of non-pathogenic and cellulolytic Bacillus licheniformis 24 as a 2,3-BD producer. By applying the Plackett–Burman design and response surface [...] Read more.
2,3-Butanediol (2,3-BD) is a reagent with remarkable commercial use as a platform chemical in numerous industries. The present study aims to determine the capabilities of non-pathogenic and cellulolytic Bacillus licheniformis 24 as a 2,3-BD producer. By applying the Plackett–Burman design and response surface methodology through central composite design (CCD), a complex optimization of medium and process parameters was conducted. Thus, among ten studied factors of medium content, four components were evaluated with a significant positive effect on 2,3-BD formation. Their optimal values for 2,3-BD production (yeast extract, 13.38 g/L; tryptone, 6.41 g/L; K2HPO4, 4.2 g/L; MgSO4, 0.32 g/L), as well as the optimal temperature (37.8 °C), pH (6.23) and aeration rate (3.68 vvm) were predicted by CCD experiments and validated in a series of batch processes. In optimized batch fermentation of 200 g/L of glucose 91.23 g/L of 2,3-BD was obtained, with the overall productivity of 1.94 g/L/h and yield of 0.488 g/g. To reveal the maximum 2,3-BD tolerance of B. licheniformis 24, fed-batch fermentation was carried out. The obtained 138.8 g/L of 2,3-BD with a yield of 0.479 g/g and productivity of 1.16 g/L/h ranks the strain among the best 2,3-BD producers. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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14 pages, 34997 KiB  
Article
Comparative Highly Efficient Production of β-glucan by Lasiodiplodia theobromae CCT 3966 and Its Multiscale Characterization
by Jesús J. Ascencio, Rafael R. Philippini, Fabricio M. Gomes, Félix M. Pereira, Silvio S. da Silva, Vinod Kumar and Anuj K. Chandel
Fermentation 2021, 7(3), 108; https://doi.org/10.3390/fermentation7030108 - 7 Jul 2021
Cited by 5 | Viewed by 2926
Abstract
Lasiodiplodan, a (1→6)-β-d-glucan, is an exopolysaccharide with high commercial value and many applications in food, pharmaceuticals, and cosmetics. Current industrial production of β-glucans from crops is mostly by chemical routes generating hazardous and toxic waste. Therefore, alternative sustainable and eco-friendly pathways are highly [...] Read more.
Lasiodiplodan, a (1→6)-β-d-glucan, is an exopolysaccharide with high commercial value and many applications in food, pharmaceuticals, and cosmetics. Current industrial production of β-glucans from crops is mostly by chemical routes generating hazardous and toxic waste. Therefore, alternative sustainable and eco-friendly pathways are highly desirable. Here, we have studied the lasiodiplodan production from sugarcane bagasse (SCB), a major lignocellulosic agricultural residue, by Lasiodiplodia theobromae CCT 3966. Lasiodiplodan accumulated on SCB hydrolysate (carbon source) supplemented with soybean bran or rice bran (nitrogen source) was 16.2 [6.8 × 103 Da] and 22.0 [7.6 × 103 Da] g/L, respectively. Lasiodiplodan showed high purity, low solubility, pseudoplastic behavior and was composed of glucose units. Moreover, the exopolysaccharides were substantially amorphous with moderate thermal stability and similar degradation temperatures. To our knowledge, this is the first report on the highest production of SCB-based lasiodiplodan to date. L. theobromae, as a microbial cell factory, demonstrated the commercial potential for the sustainable production of lasiodiplodan from renewable biomass feedstock. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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Review

Jump to: Research

18 pages, 1026 KiB  
Review
Recent Developments and Current Status of Commercial Production of Fuel Ethanol
by Tuan-Dung Hoang and Nhuan Nghiem
Fermentation 2021, 7(4), 314; https://doi.org/10.3390/fermentation7040314 - 15 Dec 2021
Cited by 50 | Viewed by 10896
Abstract
Ethanol produced from various biobased sources (bioethanol) has been gaining high attention lately due to its potential to cut down net emissions of carbon dioxide while reducing burgeoning world dependence on fossil fuels. Global ethanol production has increased more than six-fold from 18 [...] Read more.
Ethanol produced from various biobased sources (bioethanol) has been gaining high attention lately due to its potential to cut down net emissions of carbon dioxide while reducing burgeoning world dependence on fossil fuels. Global ethanol production has increased more than six-fold from 18 billion liters at the turn of the century to 110 billion liters in 2019, only to fall to 98.6 billion liters in 2020 due to the pandemic. Sugar cane and corn have been used as the major feedstocks for ethanol production. Lignocellulosic biomass has recently been considered as another potential feedstock due to its non-food competing status and its availability in very large quantities. This paper reviews recent developments and current status of commercial production of ethanol across the world with a focus on the technological aspects. The review includes the ethanol production processes used for each type of feedstock, both currently practiced at commercial scale and still under developments, and current production trends in various regions and countries in the world. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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18 pages, 941 KiB  
Review
Production of Bioethanol—A Review of Factors Affecting Ethanol Yield
by Timothy J. Tse, Daniel J. Wiens and Martin J. T. Reaney
Fermentation 2021, 7(4), 268; https://doi.org/10.3390/fermentation7040268 - 18 Nov 2021
Cited by 109 | Viewed by 67083
Abstract
Fossil fuels are a major contributor to climate change, and as the demand for energy production increases, alternative sources (e.g., renewables) are becoming more attractive. Biofuels such as bioethanol reduce reliance on fossil fuels and can be compatible with the existing fleet of [...] Read more.
Fossil fuels are a major contributor to climate change, and as the demand for energy production increases, alternative sources (e.g., renewables) are becoming more attractive. Biofuels such as bioethanol reduce reliance on fossil fuels and can be compatible with the existing fleet of internal combustion engines. Incorporation of biofuels can reduce internal combustion engine (ICE) fleet carbon dioxide emissions. Bioethanol is typically produced via microbial fermentation of fermentable sugars, such as glucose, to ethanol. Traditional feedstocks (e.g., first-generation feedstock) include cereal grains, sugar cane, and sugar beets. However, due to concerns regarding food sustainability, lignocellulosic (second-generation) and algal biomass (third-generation) feedstocks have been investigated. Ethanol yield from fermentation is dependent on a multitude of factors. This review compares bioethanol production from a range of feedstocks, and elaborates on available technologies, including fermentation practices. The importance of maintaining nutrient homeostasis of yeast is also examined. The purpose of this review is to provide industrial producers and policy makers insight into available technologies, yields of bioethanol achieved by current manufacturing practices, and goals for future innovation. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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19 pages, 1640 KiB  
Review
Value-Added Products from Ethanol Fermentation—A Review
by Timothy J. Tse, Daniel J. Wiens, Farley Chicilo, Sarah K. Purdy and Martin J. T. Reaney
Fermentation 2021, 7(4), 267; https://doi.org/10.3390/fermentation7040267 - 17 Nov 2021
Cited by 10 | Viewed by 5640
Abstract
Global demand for renewable and sustainable energy is increasing, and one of the most common biofuels is ethanol. Most ethanol is produced by Saccharomyces cerevisiae (yeast) fermentation of either crops rich in sucrose (e.g., sugar cane and sugar beet) or starch-rich crops (e.g., [...] Read more.
Global demand for renewable and sustainable energy is increasing, and one of the most common biofuels is ethanol. Most ethanol is produced by Saccharomyces cerevisiae (yeast) fermentation of either crops rich in sucrose (e.g., sugar cane and sugar beet) or starch-rich crops (e.g., corn and starchy grains). Ethanol produced from these sources is termed a first-generation biofuel. Yeast fermentation can yield a range of additional valuable co-products that accumulate during primary fermentation (e.g., protein concentrates, water soluble metabolites, fusel alcohols, and industrial enzymes). Distillers’ solubles is a liquid co-product that can be used in animal feed or as a resource for recovery of valuable materials. In some processes it is preferred that this fraction is modified by a second fermentation with another fermentation organism (e.g., lactic acid bacteria). Such two stage fermentations can produce valuable compounds, such as 1,3-propanediol, organic acids, and bacteriocins. The use of lactic acid bacteria can also lead to the aggregation of stillage proteins and enable protein aggregation into concentrates. Once concentrated, the protein has utility as a high-protein feed ingredient. After separation of protein concentrates the remaining solution is a potential source of several known small molecules. The purpose of this review is to provide policy makers, bioethanol producers, and researchers insight into additional added-value products that can be recovered from ethanol beers. Novel products may be isolated during or after distillation. The ability to isolate and purify these compounds can provide substantial additional revenue for biofuel manufacturers through the development of marketable co-products. Full article
(This article belongs to the Special Issue Ethanol and Value-Added Co-products 3.0)
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