Special Issue "Biofuels and Biochemicals Production"

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

Deadline for manuscript submissions: closed (30 April 2017)

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A printed edition of this Special Issue is available here.

Special Issue Editor

Guest Editor
Prof. Dr. Thaddeus Ezeji

Department of Animal Sciences and Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, 305 Gerlaugh Hall, 1680 Madison Avenue, Wooster, OH 44691, USA
Website | E-Mail
Interests: microbial physiology; biofuels (butanol, ethanol, methane) and biochemicals (2,3-butanediol, acetone, isopropanol) production; downstream processing; biomass pretreatment technologies; lignocellulose-derived microbial inhibitory compounds and mitigations; metabolic engineering; bioreactor design; alcoholic fermentation and anaerobic digestion

Special Issue Information

Dear Colleagues,

The high demand and depletion of petroleum reserves and the associated impact on the environment, together with volatility in the energy market price over the past three decades, have led to tremendous efforts in bio-based research activities, especially in biofuels and biochemicals. Most people associate petroleum with gasoline, however, approximately 6000 petroleum-derived products are available on the market today. Ironically, these petroleum-derived products have not elicited a high level of interest among the populace and media due, in part, to little awareness of the origins of these important products. Given the finite nature of petroleum, it is critical to devote substantial amounts of energy and resources on the development of renewable chemicals, as is currently done for fuels. Theoretically, the bioproduction of gasoline-like fuels and the 6000 petroleum-derived products are within the realm of possibility since our aquatic and terrestrial ecosystems contain abundant and diverse microorganisms capable of catalyzing unlimited numbers of reactions. Moreover, the fields of synthetic biology and metabolic engineering have evolved to the point that a wide range of microorganisms can be enticed or manipulated to catalyze foreign, or improve indigenous, biosynthetic reactions. To increase the concentration of products of interest and to ensure consistent productivity and yield, compatible fermentation processes must be used. Greater agricultural and chemical production during the past three decades, due in part to population increase and industrialization, has generated increasing levels of waste, which must be treated prior to discharge into waterways or wastewater treatment plants. Thus, in addition to the need to understand the physiology and metabolism of microbial catalysts of biotechnological significance, development of cost-effective fermentation strategies to produce biofuels and chemicals of interests while generating minimal waste, or better yet, converting waste into value-added products, is crucial. In this Special Issue, we invite authors to submit original research and review articles that increase our understanding of fermentation technology vis-à-vis production of liquid biofuels and biochemicals, and fermentation strategies that alleviate product toxicity to the fermenting microorganism while enhancing productivity. Further, original research articles and reviews focused on anaerobic digestion, production of gaseous biofuels, fermentation optimization using modelling and simulations, metabolic engineering, or development of tailor-made fermentation processes are welcome.

 

Prof. Dr. Thaddeus Ezeji
Guest Editor

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 quarterly journal published by MDPI.

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Keywords

  • anaerobic digestion
  • biogas
  • bioreactors
  • biotransformation
  • butanediol
  • butanol
  • butyric acid
  • Clostridium acetobutylicum
  • Clostridium beijerinckii
  • Clostridium pasteurianum
  • co-culture
  • co-fermentation
  • cofactors
  • corn stover
  • ethanol
  • Escherichia coli
  • furfural
  • glycerol
  • hydroxymethyl furfural (HMF)
  • isopropanol
  • lactic acid
  • lignocellulose
  • lignocellulose derived microbial inhibitory compounds (LDMICs)
  • metabolic engineering
  • microalgae
  • Miscanthus giganteus
  • mixed sugars fermentation
  • phenolic compounds
  • process integration
  • propanediol
  • redox
  • simultaneous saccharification and fermentation (SSF)
  • succinic acid
  • switchgrass
  • syngas fermentation
  • synthetic biology
  • techno-economics of production
  • transcriptomics

Published Papers (14 papers)

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Editorial

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Open AccessEditorial Production of Bio-Derived Fuels and Chemicals
Fermentation 2017, 3(3), 42; https://doi.org/10.3390/fermentation3030042
Received: 28 August 2017 / Revised: 28 August 2017 / Accepted: 28 August 2017 / Published: 30 August 2017
Cited by 1 | PDF Full-text (175 KB) | HTML Full-text | XML Full-text
Abstract
The great demand for, and impending depletion of petroleum reserves, the associated impact of fossil fuel consumption on the environment, and volatility in the energy market have elicited extensive research on alternative sources of traditional petroleum-derived products such as biofuels and bio-chemicals.[...] Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available

Research

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Open AccessArticle Phenols Removal from Hemicelluloses Pre-Hydrolysate by Laccase to Improve Butanol Production
Fermentation 2017, 3(3), 31; https://doi.org/10.3390/fermentation3030031
Received: 9 May 2017 / Revised: 23 June 2017 / Accepted: 26 June 2017 / Published: 30 June 2017
Cited by 1 | PDF Full-text (1365 KB) | HTML Full-text | XML Full-text
Abstract
Phenolic compounds are important inhibitors of the microorganisms used in the Acetone-Butanol-Ethanol (ABE) fermentation. The degradation of phenolic compounds in a wood pre-hydrolysate, a potential substrate for the production of ABE, was studied in this article. First, physicochemical methods for detoxification such as
[...] Read more.
Phenolic compounds are important inhibitors of the microorganisms used in the Acetone-Butanol-Ethanol (ABE) fermentation. The degradation of phenolic compounds in a wood pre-hydrolysate, a potential substrate for the production of ABE, was studied in this article. First, physicochemical methods for detoxification such as nanofiltration and flocculation were applied and the best combination was selected. With a flocculated sample, the concentration of phenolic compounds decreases from 1.20 to 0.28 g/L with the addition of a solid laccase at optimum conditions, which is below the phenolic compounds limit of inhibition. This results in an increase in butanol production, more than double, compared to a pre-hydrolysate non-treated with laccase enzymes. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Production of Bioethanol from Agricultural Wastes Using Residual Thermal Energy of a Cogeneration Plant in the Distillation Phase
Fermentation 2017, 3(2), 24; https://doi.org/10.3390/fermentation3020024
Received: 27 March 2017 / Revised: 19 May 2017 / Accepted: 21 May 2017 / Published: 25 May 2017
Cited by 5 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Alcoholic fermentations were performed, adapting the technology to exploit the residual thermal energy (hot water at 83–85 °C) of a cogeneration plant and to valorize agricultural wastes. Substrates were apple, kiwifruit, and peaches wastes; and corn threshing residue (CTR). Saccharomyces bayanus was chosen
[...] Read more.
Alcoholic fermentations were performed, adapting the technology to exploit the residual thermal energy (hot water at 83–85 °C) of a cogeneration plant and to valorize agricultural wastes. Substrates were apple, kiwifruit, and peaches wastes; and corn threshing residue (CTR). Saccharomyces bayanus was chosen as starter yeast. The fruits, fresh or blanched, were mashed; CTR was gelatinized and liquefied by adding Liquozyme® SC DS (Novozymes, Dittingen, Switzerland); saccharification simultaneous to fermentation was carried out using the enzyme Spirizyme® Ultra (Novozymes, Dittingen, Switzerland). Lab-scale static fermentations were carried out at 28 °C and 35 °C, using raw fruits, blanched fruits and CTR, monitoring the ethanol production. The highest ethanol production was reached with CTR (10.22% (v/v) and among fruits with apple (8.71% (v/v)). Distillations at low temperatures and under vacuum, to exploit warm water from a cogeneration plant, were tested. Vacuum simple batch distillation by rotary evaporation at lab scale at 80 °C (heating bath) and 200 mbar or 400 mbar allowed to recover 93.35% (v/v) and 89.59% (v/v) of ethanol, respectively. These results support a fermentation process coupled to a cogeneration plant, fed with apple wastes and with CTR when apple wastes are not available, where hot water from cogeneration plant is used in blanching and distillation phases. The scale up in a pilot plant was also carried out. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Continuous Ethanol Production from Synthesis Gas by Clostridium ragsdalei in a Trickle-Bed Reactor
Fermentation 2017, 3(2), 23; https://doi.org/10.3390/fermentation3020023
Received: 27 March 2017 / Revised: 7 May 2017 / Accepted: 18 May 2017 / Published: 24 May 2017
Cited by 7 | PDF Full-text (1394 KB) | HTML Full-text | XML Full-text
Abstract
A trickle-bed reactor (TBR) when operated in a trickle flow regime reduces liquid resistance to mass transfer because a very thin liquid film is in contact with the gas phase and results in improved gas–liquid mass transfer compared to continuous stirred tank reactors
[...] Read more.
A trickle-bed reactor (TBR) when operated in a trickle flow regime reduces liquid resistance to mass transfer because a very thin liquid film is in contact with the gas phase and results in improved gas–liquid mass transfer compared to continuous stirred tank reactors (CSTRs). In the present study, continuous syngas fermentation was performed in a 1-L TBR for ethanol production by Clostridium ragsdalei. The effects of dilution and gas flow rates on product formation, productivity, gas uptakes and conversion efficiencies were examined. Results showed that CO and H2 conversion efficiencies reached over 90% when the gas flow rate was maintained between 1.5 and 2.8 standard cubic centimeters per minute (sccm) at a dilution rate of 0.009 h−1. A 4:1 molar ratio of ethanol to acetic acid was achieved in co-current continuous mode with both gas and liquid entered the TBR at the top and exited from the bottom at dilution rates of 0.009 and 0.012 h−1, and gas flow rates from 10.1 to 12.2 sccm and 15.9 to 18.9 sccm, respectively. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Kinetics of Bioethanol Production from Waste Sorghum Leaves Using Saccharomyces cerevisiae BY4743
Fermentation 2017, 3(2), 19; https://doi.org/10.3390/fermentation3020019
Received: 16 January 2017 / Revised: 28 April 2017 / Accepted: 2 May 2017 / Published: 8 May 2017
Cited by 2 | PDF Full-text (1084 KB) | HTML Full-text | XML Full-text
Abstract
Kinetic models for bioethanol production from waste sorghum leaves by Saccharomyces cerevisiae BY4743 are presented. Fermentation processes were carried out at varied initial glucose concentrations (12.5–30.0 g/L). Experimental data on cell growth and substrate utilisation fit the Monod kinetic model with a coefficient
[...] Read more.
Kinetic models for bioethanol production from waste sorghum leaves by Saccharomyces cerevisiae BY4743 are presented. Fermentation processes were carried out at varied initial glucose concentrations (12.5–30.0 g/L). Experimental data on cell growth and substrate utilisation fit the Monod kinetic model with a coefficient of determination (R2) of 0.95. A maximum specific growth rate (μmax) and Monod constant (KS) of 0.176 h−1 and 10.11 g/L, respectively, were obtained. The bioethanol production data fit the modified Gompertz model with an R2 value of 0.98. A maximum bioethanol production rate (rp,m) of 0.52 g/L/h, maximum potential bioethanol concentration (Pm) of 17.15 g/L, and a bioethanol production lag time (tL) of 6.31 h were observed. The obtained Monod and modified Gompertz coefficients indicated that waste sorghum leaves can serve as an efficient substrate for bioethanol production. These models with high accuracy are suitable for the scale-up development of bioethanol production from lignocellulosic feedstocks such as sorghum leaves. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessFeature PaperArticle Process Development for Enhanced 2,3-Butanediol Production by Paenibacillus polymyxa DSM 365
Fermentation 2017, 3(2), 18; https://doi.org/10.3390/fermentation3020018
Received: 9 March 2017 / Revised: 21 April 2017 / Accepted: 2 May 2017 / Published: 7 May 2017
Cited by 2 | PDF Full-text (723 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
While chiral 2,3-Butanediol (2,3-BD) is currently receiving remarkable attention because of its numerous industrial applications in the synthetic rubber, bioplastics, cosmetics, and flavor industries, 2,3-BD-mediated feedback inhibition of Paenibacillus polymyxa DSM 365 limits the accumulation of higher concentrations of 2,3-BD in the bioreactor
[...] Read more.
While chiral 2,3-Butanediol (2,3-BD) is currently receiving remarkable attention because of its numerous industrial applications in the synthetic rubber, bioplastics, cosmetics, and flavor industries, 2,3-BD-mediated feedback inhibition of Paenibacillus polymyxa DSM 365 limits the accumulation of higher concentrations of 2,3-BD in the bioreactor during fermentation. The Box-Behnken design, Plackett-Burman design (PBD), and response surface methodology were employed to evaluate the impacts of seven factors including tryptone, yeast extract, ammonium acetate, ammonium sulfate, glycerol concentrations, temperature, and inoculum size on 2,3-butanediol (2,3-BD) production by Paenibacillus polymyxa DSM 365. Results showed that three factors; tryptone, temperature, and inoculum size significantly influence 2,3-BD production (p < 0.05) by P. polymyxa. The optimal levels of tryptone, inoculum size, and temperature as determined by the Box-Behnken design and response surface methodology were 3.5 g/L, 9.5%, and 35 °C, respectively. The optimized process was validated in batch and fed-batch fermentations in a 5-L Bioflo 3000 Bioreactor, and 51.10 and 68.54 g/L 2,3-BD were obtained, respectively. Interestingly, the production of exopolysaccharides (EPS), an undesirable co-product, was reduced by 19% when compared to the control. These results underscore an interplay between medium components and fermentation conditions, leading to increased 2,3-BD production and decreased EPS production by P. polymyxa. Collectively, our findings demonstrate both increased 2,3-BD titer, a fundamental prerequisite to the potential commercialization of fermentative 2,3-BD production using renewable feedstocks, and reduced flux of carbons towards undesirable EPS production. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessFeature PaperArticle A Sequential Steam Explosion and Reactive Extrusion Pretreatment for Lignocellulosic Biomass Conversion within a Fermentation-Based Biorefinery Perspective
Fermentation 2017, 3(2), 15; https://doi.org/10.3390/fermentation3020015
Received: 16 March 2017 / Revised: 12 April 2017 / Accepted: 14 April 2017 / Published: 20 April 2017
Cited by 2 | PDF Full-text (1523 KB) | HTML Full-text | XML Full-text
Abstract
The present work evaluates a two-step pretreatment process based on steam explosion and extrusion technologies for the optimal fractionation of lignocellulosic biomass. Two-step pretreatment of barley straw resulted in overall glucan, hemicellulose and lignin recovery yields of 84%, 91% and 87%, respectively. Precipitation
[...] Read more.
The present work evaluates a two-step pretreatment process based on steam explosion and extrusion technologies for the optimal fractionation of lignocellulosic biomass. Two-step pretreatment of barley straw resulted in overall glucan, hemicellulose and lignin recovery yields of 84%, 91% and 87%, respectively. Precipitation of the collected lignin-rich liquid fraction yielded a solid residue with high lignin content, offering possibilities for subsequent applications. Moreover, hydrolysability tests showed almost complete saccharification of the pretreated solid residue, which when combined with the low concentration of the generated inhibitory compounds, is representative of a good pretreatment approach. Scheffersomyces stipitis was capable of fermenting all of the glucose and xylose from the non-diluted hemicellulose fraction, resulting in an ethanol concentration of 17.5 g/L with 0.34 g/g yields. Similarly, Saccharomyces cerevisiae produced about 4% (v/v) ethanol concentration with 0.40 g/g yields, during simultaneous saccharification and fermentation (SSF) of the two-step pretreated solid residue at 10% (w/w) consistency. These results increased the overall conversion yields from a one-step steam explosion pretreatment by 1.4-fold, showing the effectiveness of including an extrusion step to enhance overall biomass fractionation and carbohydrates conversion via microbial fermentation processes. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Anhydrous Ammonia Pretreatment of Corn Stover and Enzymatic Hydrolysis of Glucan from Pretreated Corn Stover
Received: 27 October 2016 / Revised: 15 February 2017 / Accepted: 15 February 2017 / Published: 17 February 2017
Cited by 1 | PDF Full-text (788 KB) | HTML Full-text | XML Full-text
Abstract
As a promising alternative of fossil fuel, ethanol has been widely used. In recent years, much attention has been devoted to bioethanol production from lignocellulosic biomass. In previous research, it is found that the pretreatment method named low-moisture anhydrous ammonia (LMAA) has the
[...] Read more.
As a promising alternative of fossil fuel, ethanol has been widely used. In recent years, much attention has been devoted to bioethanol production from lignocellulosic biomass. In previous research, it is found that the pretreatment method named low-moisture anhydrous ammonia (LMAA) has the advantage of high conversion efficiency and less washing requirements. The purpose of this study was to explore the optimal conditions by employing the LMAA pretreatment method. Corn stover was treated under three levels of moisture content: 20, 50, 80 w.b.% (wet basis), and three levels of particle size: <0.09, 0.09–2, >2 mm; it was also ammoniated with a loading rate of 0.1g NH3/g biomass (dry matter). Ammoniated corn stover was then subjected to different pretreatment times (24, 96, 168 h) and temperatures (20, 75, 130 °C). After pretreatment, compositional analysis and enzymatic digestibility were conducted to determine the highest glucose yield. As a result, the highest glucose yield was obtained under the condition of 96 h and 75 °C with 50 w.b.% and 0.09–2 mm of corn stover. The main findings of this study could improve the efficiency of bioethanol production processing in the near future. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessFeature PaperArticle Assessment of Acidified Fibrous Immobilization Materials for Improving Acetone-Butanol-Ethanol (ABE) Fermentation
Received: 13 October 2016 / Revised: 15 December 2016 / Accepted: 23 December 2016 / Published: 30 December 2016
Cited by 2 | PDF Full-text (3612 KB) | HTML Full-text | XML Full-text
Abstract
Acetone-butanol-ethanol (ABE) fermentation using Clostridium acetobutylicum is a process that can be used to produce butanol, which can be utilized as an alternative to petroleum-based fuels. Immobilization of the bacteria using three different fibrous materials was studied in order to see how to
[...] Read more.
Acetone-butanol-ethanol (ABE) fermentation using Clostridium acetobutylicum is a process that can be used to produce butanol, which can be utilized as an alternative to petroleum-based fuels. Immobilization of the bacteria using three different fibrous materials was studied in order to see how to improve the ABE fermentation process. The results were compared to those of non-immobilized bacteria. Modal and charcoal fibers had OD levels below one at 72 h with the butanol concentration reaching 11.0 ± 0.5 and 10.7 ± 0.6 g/L, respectively, each of which were close to the free cell concentration at 11.1 ± 0.4 g/L. This suggests that bacteria can be efficiently immobilized in these fibrous materials. Although an extended lag phase was found in the fermentation time course, this can be easily solved by pre-treating fibrous materials with 3.5% HCl for 12 h. From comparisons with previous studies, data in this study suggests that a hydrophilic surface facilitates the adsorption of C. acetobutylicum. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Cellulase Production from Bacillus subtilis SV1 and Its Application Potential for Saccharification of Ionic Liquid Pretreated Pine Needle Biomass under One Pot Consolidated Bioprocess
Fermentation 2016, 2(4), 19; https://doi.org/10.3390/fermentation2040019
Received: 29 August 2016 / Revised: 3 November 2016 / Accepted: 8 November 2016 / Published: 23 November 2016
Cited by 6 | PDF Full-text (2396 KB) | HTML Full-text | XML Full-text
Abstract
Pretreatment is the requisite step for the bioconversion of lignocellulosics. Since most of the pretreatment strategies are cost/energy intensive and environmentally hazardous, there is a need for the development of an environment-friendly pretreatment process. An ionic liquid (IL) based pretreatment approach has recently
[...] Read more.
Pretreatment is the requisite step for the bioconversion of lignocellulosics. Since most of the pretreatment strategies are cost/energy intensive and environmentally hazardous, there is a need for the development of an environment-friendly pretreatment process. An ionic liquid (IL) based pretreatment approach has recently emerged as the most appropriate one as it can be accomplished under ambient process conditions. However, IL-pretreated biomass needs extensive washing prior to enzymatic saccharification as the enzymes may be inhibited by the residual IL. This necessitated the exploration of IL-stable saccharification enzymes (cellulases). Current study aims at optimizing the bioprocess variables viz. carbon/nitrogen sources, medium pH and fermentation time, by using a Design of Experiments approach for achieving enhanced production of ionic liquid tolerant cellulase from a bacterial isolate Bacillus subtilis SV1. The cellulase production was increased by 1.41-fold as compared to that under unoptimized conditions. IL-stable cellulase was employed for saccharification of IL (1-ethyl-3-methylimidazolium methanesulfonate) pretreated pine needle biomass in a newly designed bioprocess named as “one pot consolidated bioprocess” (OPCB), and a saccharification efficiency of 65.9% was obtained. Consolidated bioprocesses, i.e., OPCB, offer numerous techno-economic advantages over conventional multistep processes, and may potentially pave the way for successful biorefining of biomass to biofuel, and other commercial products. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessArticle Modelling and Optimization of Operational Setpoint Parameters for Maximum Fermentative Biohydrogen Production Using Box-Behnken Design
Fermentation 2016, 2(3), 15; https://doi.org/10.3390/fermentation2030015
Received: 3 June 2016 / Revised: 10 July 2016 / Accepted: 15 July 2016 / Published: 20 July 2016
Cited by 4 | PDF Full-text (2682 KB) | HTML Full-text | XML Full-text
Abstract
Fermentative biohydrogen production has been flagged as a future alternative energy source due to its various socio-economical benefits. Currently, its production is hindered by the low yield. In this work, modelling and optimization of fermentative biohydrogen producing operational setpoint conditions was carried out.
[...] Read more.
Fermentative biohydrogen production has been flagged as a future alternative energy source due to its various socio-economical benefits. Currently, its production is hindered by the low yield. In this work, modelling and optimization of fermentative biohydrogen producing operational setpoint conditions was carried out. A box-behnken design was used to generate twenty-nine batch experiments. The experimental data were used to produce a quadratic polynomial model which was subjected to analysis of variance (ANOVA) to evaluate its statistical significance. The quadratic polynomial model had a coefficient of determination (R2) of 0.7895. The optimum setpoint obtained were potato-waste concentration 39.56 g/L, pH 5.56, temperature 37.87 °C, and fermentation time 82.58 h, predicting a biohydrogen production response of 537.5 mL H2/g TVS. A validation experiment gave 603.5 mL H2/g TVS resulting to a 12% increase. The R2 was above 0.7 implying the model was adequate to navigate the optimization space. Therefore, these findings demonstrated the feasibility of conducting optimized biohydrogen fermentation processes using response surface methodology. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Review

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Open AccessFeature PaperReview Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products
Fermentation 2017, 3(2), 28; https://doi.org/10.3390/fermentation3020028
Received: 27 April 2017 / Revised: 9 June 2017 / Accepted: 12 June 2017 / Published: 16 June 2017
Cited by 6 | PDF Full-text (1506 KB) | HTML Full-text | XML Full-text
Abstract
Biomass and other carbonaceous materials can be gasified to produce syngas with high concentrations of CO and H2. Feedstock materials include wood, dedicated energy crops, grain wastes, manufacturing or municipal wastes, natural gas, petroleum and chemical wastes, lignin, coal and tires.
[...] Read more.
Biomass and other carbonaceous materials can be gasified to produce syngas with high concentrations of CO and H2. Feedstock materials include wood, dedicated energy crops, grain wastes, manufacturing or municipal wastes, natural gas, petroleum and chemical wastes, lignin, coal and tires. Syngas fermentation converts CO and H2 to alcohols and organic acids and uses concepts applicable in fermentation of gas phase substrates. The growth of chemoautotrophic microbes produces a wide range of chemicals from the enzyme platform of native organisms. In this review paper, the Wood–Ljungdahl biochemical pathway used by chemoautotrophs is described including balanced reactions, reaction sites physically located within the cell and cell mechanisms for energy conservation that govern production. Important concepts discussed include gas solubility, mass transfer, thermodynamics of enzyme-catalyzed reactions, electrochemistry and cellular electron carriers and fermentation kinetics. Potential applications of these concepts include acid and alcohol production, hydrogen generation and conversion of methane to liquids or hydrogen. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Open AccessFeature PaperReview Laccases as a Potential Tool for the Efficient Conversion of Lignocellulosic Biomass: A Review
Fermentation 2017, 3(2), 17; https://doi.org/10.3390/fermentation3020017
Received: 26 March 2017 / Revised: 20 April 2017 / Accepted: 26 April 2017 / Published: 2 May 2017
Cited by 8 | PDF Full-text (864 KB) | HTML Full-text | XML Full-text
Abstract
The continuous increase in the world energy and chemicals demand requires the development of sustainable alternatives to non-renewable sources of energy. Biomass facilities and biorefineries represent interesting options to gradually replace the present industry based on fossil fuels. Lignocellulose is the most promising
[...] Read more.
The continuous increase in the world energy and chemicals demand requires the development of sustainable alternatives to non-renewable sources of energy. Biomass facilities and biorefineries represent interesting options to gradually replace the present industry based on fossil fuels. Lignocellulose is the most promising feedstock to be used in biorefineries. From a sugar platform perspective, a wide range of fuels and chemicals can be obtained via microbial fermentation processes, being ethanol the most significant lignocellulose-derived fuel. Before fermentation, lignocellulose must be pretreated to overcome its inherent recalcitrant structure and obtain the fermentable sugars. Usually, harsh conditions are required for pretreatment of lignocellulose, producing biomass degradation and releasing different compounds that are inhibitors of the hydrolytic enzymes and fermenting microorganisms. Moreover, the lignin polymer that remains in pretreated materials also affects biomass conversion by limiting the enzymatic hydrolysis. The use of laccases has been considered as a very powerful tool for delignification and detoxification of pretreated lignocellulosic materials, boosting subsequent saccharification and fermentation processes. This review compiles the latest studies about the application of laccases as useful and environmentally friendly delignification and detoxification technology, highlighting the main challenges and possible ways to make possible the integration of these enzymes in future lignocellulose-based industries. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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Other

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Open AccessTechnical Note Simultaneous Determination of Sugars, Carboxylates, Alcohols and Aldehydes from Fermentations by High Performance Liquid Chromatography
Received: 29 January 2016 / Revised: 23 February 2016 / Accepted: 24 February 2016 / Published: 7 March 2016
Cited by 7 | PDF Full-text (2046 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Despite the rise of ‘omics techniques for the study of biological systems, the quantitative description of phenotypes still rests to a large extent on quantitative data produced on chromatography platforms. Here, we describe an improved liquid chromatography method for the determination of sugars,
[...] Read more.
Despite the rise of ‘omics techniques for the study of biological systems, the quantitative description of phenotypes still rests to a large extent on quantitative data produced on chromatography platforms. Here, we describe an improved liquid chromatography method for the determination of sugars, carboxylates, alcohols and aldehydes in microbial fermentation samples and cell extracts. Specific emphasis is given to substrates and products currently pursued in industrial microbiology. The present method allows quantification of 21 compounds in a single run with limits of quantification between 10−7 and 10−10 mol and limits of detection between 10−9 and 10−11 mol. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production) Printed Edition available
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