Bioethanol Production via Syngas Fermentation

Bioconversion of C-1 carbon in syngas through microbial fermentation presents a huge potential to be further explored for ethanol production. Syngas can be obtained from the gasification of lignocellulosic biomass, by which most of carbon content of the biomass was converted into CO and CO2. These gases could be further utilized by carbon-fixing microorganism such as Clostridium sp. to produce ethanol as the end product. In order to obtain an optimum process, a robust and high performance strain is required and thus high ethanol yield as the main product can be expected. In this study, series of batch fermentation was carried out to select high performance strains for ethanol production. Bottle serum fermentations were performed using CO-gas as the sole carbon source to evaluate the potential of some Clostridia species such as Clostridium ljungdahlii, C. ragsdalei, and C. carboxidovorans in producing ethanol at various concentration of yeast extract as the organic nitrogen source, salt concentration, and buffer composition. Strain with the highest ethanol production in the optimum media will be further utilized in the upscale fermentation.

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Both adhE and a Separate NADPH-Dependent Alcohol Dehydrogenase Gene, adhA, Are Necessary for High Ethanol Production in Thermoanaerobacterium saccharolyticum

Journal of Bacteriology ◽

10.1128/jb.00542-16 ◽

2016 ◽

Vol 199 (3) ◽

Cited By ~ 18

Author(s):

Tianyong Zheng ◽

Daniel G. Olson ◽

Sean J. Murphy ◽

Xiongjun Shao ◽

Liang Tian ◽

...

Keyword(s):

Alcohol Dehydrogenase ◽

Ethanol Production ◽

Ethanol Yield ◽

Single Gene ◽

Maximum Yield ◽

Primary Alcohol ◽

Content Type ◽

Thermoanaerobacterium Saccharolyticum ◽

Dehydrogenase Gene ◽

High Ethanol

ABSTRACT Thermoanaerobacterium saccharolyticum has been engineered to produce ethanol at about 90% of the theoretical maximum yield (2 ethanol molecules per glucose equivalent) and a titer of 70 g/liter. Its ethanol-producing ability has drawn attention to its metabolic pathways, which could potentially be transferred to other organisms of interest. Here, we report that the iron-containing AdhA is important for ethanol production in the high-ethanol strain of T. saccharolyticum (LL1049). A single-gene deletion of adhA in LL1049 reduced ethanol production by ∼50%, whereas multiple gene deletions of all annotated alcohol dehydrogenase genes except adhA and adhE did not affect ethanol production. Deletion of adhA in wild-type T. saccharolyticum reduced NADPH-linked alcohol dehydrogenase (ADH) activity (acetaldehyde-reducing direction) by 93%. IMPORTANCE In this study, we set out to identify the alcohol dehydrogenases necessary for high ethanol production in T. saccharolyticum. Based on previous work, we had assumed that adhE was the primary alcohol dehydrogenase gene. Here, we show that both adhA and adhE are needed for high ethanol yield in the engineered strain LL1049. This is the first report showing adhA is important for ethanol production in a native adhA host, which has important implications for achieving higher ethanol yields in other microorganisms.

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Ethanol Metabolism Dynamics in Clostridium ljungdahlii Grown on Carbon Monoxide

Applied and Environmental Microbiology ◽

10.1128/aem.00730-20 ◽

2020 ◽

Vol 86 (14) ◽

Cited By ~ 2

Author(s):

Zi-Yong Liu ◽

De-Chen Jia ◽

Kun-Di Zhang ◽

Hai-Feng Zhu ◽

Quan Zhang ◽

...

Keyword(s):

Carbon Monoxide ◽

Ethanol Production ◽

Biomass Production ◽

Ethanol Oxidation ◽

Ethanol Yield ◽

Ethanol Metabolism ◽

Content Type ◽

Atp Production ◽

Clostridium Ljungdahlii ◽

Gas Fermentation

ABSTRACT Bioethanol production from syngas using acetogenic bacteria has attracted considerable attention in recent years. However, low ethanol yield is the biggest challenge that prevents the commercialization of syngas fermentation into biofuels using microbial catalysts. The present study demonstrated that ethanol metabolism plays an important role in recycling NADH/NAD+ during autotrophic growth. Deletion of bifunctional aldehyde/alcohol dehydrogenase (adhE) genes leads to significant growth deficiencies in gas fermentation. Using specific fermentation technology in which the gas pressure and pH were constantly controlled at 0.1 MPa and 6.0, respectively, we revealed that ethanol was formed during the exponential phase, closely accompanied by biomass production. Then, ethanol was oxidized to acetate via the aldehyde ferredoxin oxidoreductase pathway in Clostridium ljungdahlii. A metabolic experiment using 13C-labeled ethanol and acetate, redox balance analysis, and comparative transcriptomic analysis demonstrated that ethanol production and reuse shared the metabolic pathway but occurred at different growth phases. IMPORTANCE Ethanol production from carbon monoxide (CO) as a carbon and energy source by Clostridium ljungdahlii and “Clostridium autoethanogenum” is currently being commercialized. During gas fermentation, ethanol synthesis is NADH-dependent. However, ethanol oxidation and its regulatory mechanism remain incompletely understood. Energy metabolism analysis demonstrated that reduced ferredoxin is the sole source of NADH formation by the Rnf-ATPase system, which provides ATP for cell growth during CO fermentation. Therefore, ethanol production is tightly linked to biomass production (ATP production). Clarification of the mechanism of ethanol oxidation and biosynthesis can provide an important reference for generating high-ethanol-yield strains of C. ljungdahlii in the future.

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Ethanol Production Potential of Sweet Sorghum in North and Central Ukraine

The Open Agriculture Journal ◽

10.2174/1874331502014010321 ◽

2020 ◽

Vol 14 (1) ◽

pp. 321-338

Author(s):

Svitlana O. Rakhmetova ◽

Olena M. Vergun ◽

Rostislav Y. Blume ◽

Oleksandr P. Bondarchuk ◽

Oksana V. Shymanska ◽

...

Keyword(s):

Ethanol Production ◽

Sweet Sorghum ◽

High Performance ◽

Second Generation ◽

Ethanol Yield ◽

Ethanol Productivity ◽

Green Economy ◽

Yield Potential ◽

Dry Matter Content ◽

Sorghum Genotypes

Background: Sweet sorghum (Sorghum saccharatum (L.) Moench) is a unique crop with great potential to serve both the food and energy industries. It is due to the possibility of (bio)ethanol production both from the juice and biomass of this crop. The sorghum stems juice contains sugar in the levels similar to that of sugarcane. Besides, low cultivation requirements for the sweet sorghum make this crop even more attractive for sugar and ethanol production. In terms of technology, sweet sorghum is seen as a transitional feedstock for the first to the second generation bioethanol production. However, effective technological development of the plant cultivation and processing in the Northern and Central Ukraine is restrained by the lack of a collection of sweet sorghum genotypes and adapted varieties for its large-scale cultivation. Additionally, no evaluations of potential (bio)ethanol productivity have been performed for this region, which is important for efficient implementation of novel biofuel-producing technologies and for successful development of a green economy. Objective: This research was aimed to create a pool of sweet sorghum genotypes with the involvement of worldwide germplasm, analyze their morphology and breed high-yielding plant lines for the efficient production of liquid biofuels for second-generation bioenergy. Based on that, we also aimed to explore the prospects regarding the efficiency of sweet sorghum cultivation for (bio)ethanol production in the Northern and Central Ukraine. Methods and Materials: A valuable gene pool of S. saccharatum (L.) Moench (41 samples) was created; in particular, high-performance genotypes were created for cultivation under the soil-climatic conditions of Ukraine. The bio-morphological features and the yield potential of the plants were determined and the biochemical composition of the phyto-raw materials was determined in different periods of vegetation, in particular, during the technical ripeness of the above-ground mass of plants. The more productive forms and varieties of sugar sorghum in terms of yield, dry matter content, sugar, and energy value of biomass during flowering and waxy ripeness are highlighted. The technological properties of plant biomass for the production of alternative liquid fuels (in particular, bioethanol) have been analyzed. Importantly, optimal cultivation conditions have been elaborated for the newly created sweet sorghum genotypes, and their productivity has also been evaluated. Moreover, for the first time, a detailed study on potential ethanol yield has been conducted. Results: Sweet sorghum has considerable potential in Ukraine as a new sugar-producing energy crop. The germplasm collection of this crop has been created (41 accessions), including introduced and acclimated genotypes and newly bred lines and varieties. The biological performance of sorghum in Ukraine and plant morphology have been analyzed. The most promising genotypes were used for breeding of new high-productive sweet sorghum varieties. The potential (bio)ethanol yield for different sugar feedstocks (juice, grain bagasse) can reach up to 11423 L/ha in total from juice, grain and bagasse. Conclusion: The estimated values of ethanol productivity are comparable to the results of other similar investigations. In conclusion, a high performance of sweet sorghum in Ukraine can be suggested.

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High Ethanol Titers from Cellulose by Using Metabolically Engineered Thermophilic, Anaerobic Microbes

Applied and Environmental Microbiology ◽

10.1128/aem.00646-11 ◽

2011 ◽

Vol 77 (23) ◽

pp. 8288-8294 ◽

Cited By ~ 202

Author(s):

D. Aaron Argyros ◽

Shital A. Tripathi ◽

Trisha F. Barrett ◽

Stephen R. Rogers ◽

Lawrence F. Feinberg ◽

...

Keyword(s):

Ethanol Production ◽

Wild Type Strain ◽

Ethanol Yield ◽

Fold Increase ◽

Substantial Improvement ◽

Wild Type ◽

Content Type ◽

Thermoanaerobacterium Saccharolyticum ◽

Lactic Acids ◽

High Ethanol

ABSTRACTThis work describes novel genetic tools for use inClostridium thermocellumthat allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the nativeC. thermocellum hptgene and theThermoanaerobacterium saccharolyticum tdkgene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The ΔldhΔptamutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of bothC. thermocellumandT. saccharolyticum. Fermentation of 92 g/liter Avicel by this coculture resulted in 38 g/liter ethanol, with acetic and lactic acids below detection limits, in 146 h. These results demonstrate that ethanol production by thermophilic, cellulolytic microbes is amenable to substantial improvement by metabolic engineering.

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Enzymatic Process for Cystoseira barbata Valorization: Ethanol Production and Additional By-Products

Processes ◽

10.3390/pr9050741 ◽

2021 ◽

Vol 9 (5) ◽

pp. 741

Author(s):

Doinita-Roxana Cioroiu Tirpan ◽

Ancaelena Eliza Sterpu ◽

Claudia Irina Koncsag ◽

Alina Georgiana Ciufu ◽

Tănase Dobre

Keyword(s):

Ethanol Production ◽

Alcoholic Fermentation ◽

Ethanol Yield ◽

Product Yield ◽

Liquid Ratio ◽

Experimental Conditions ◽

Factors Affecting ◽

Cystoseira Barbata ◽

Main Factors ◽

Process Factors

The aim of this study is to evaluate the potential of dried Cystoseira barbata alga for ethanol production through alcoholic fermentation. The influence of the main factors affecting the fermentation are studied in the frame of a 23 factorial experimental plan. The main factors influencing the process are the fermentation temperature (t from 25 °C to 35 °C), the solid to liquid ratio (S/L from 0.040 g/g to 0.080 g/g), and the cellulase ratio (R from 8 U/g d.m to 16 U/g d.m.). The maximum volatile compounds yield of 0.2808 g/g d.m and ethanol yield of 0.0158 g/g d.m were favored by the following experimental conditions: process temperature of 35 °C, solid to liquid ratio of 0.0415, and enzyme ratio of 16 U/g d.m. A statistical model was used to correlate the product yield with the process factors. Additionally, 19 interesting bioactive compounds were found in the enzymatic hydrolysis and alcoholic fermentation broths which seem likely to maintain natural defence mechanisms against diseases and physical disorders.

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Hemicellulosic Bioethanol Production from Fast-Growing Paulownia Biomass

Processes ◽

10.3390/pr9010173 ◽

2021 ◽

Vol 9 (1) ◽

pp. 173

Author(s):

Elena Domínguez ◽

Pablo G. del Río ◽

Aloia Romaní ◽

Gil Garrote ◽

Lucília Domingues

Keyword(s):

Ethanol Production ◽

Ethanol Concentration ◽

Ethanol Yield ◽

Xylose Reductase ◽

Energy Crop ◽

Scheffersomyces Stipitis ◽

Fractionation Process ◽

Renewable Source ◽

Fast Growing ◽

Engineered Strain

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S0 of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach.

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Effects of carbon concentration, oxygen, and controlled pH on the engineering strain Lactiplantibacillus casei E1 in the production of bioethanol from sugarcane molasses

AMB Express ◽

10.1186/s13568-021-01257-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Song Wang ◽

Ran Tian ◽

Buwei Liu ◽

Hongcai Wang ◽

Jun Liu ◽

...

Keyword(s):

Lactic Acid ◽

Lactic Acid Bacteria ◽

High Performance ◽

Ethanol Yield ◽

Starter Culture ◽

Market Price ◽

Sugarcane Molasses ◽

Engineering Strain ◽

Carbohydrate Utilization ◽

Cane Molasses

AbstractSugarcane molasses are considered a potential source for bioethanol’s commercial production because of its availability and low market price. It contains high concentrations of fermentable sugars that can be directly metabolized by microbial fermentation. Heterofermentative lactic acid bacteria, especially Lactiplantibacillus casei, have a high potential to be a biocatalyst in ethanol production that they are characterized by strong abilities of carbohydrate metabolism, ethanol synthesis, and high alcohol tolerance. This study aimed to evaluate the feasibility of producing ethanol by Lactiplantibacillus casei used the ethanologen engineering strain L. casei E1 as a starter culture and cane molasses as substrate medium. The effects of environmental factors on the metabolism of L. casei E1 were analyzed by high-performance liquid chromatography (HPLC) system, and the gene expression of key enzymes in carbon source metabolism was detected using quantitative real-time PCR (RT–qPCR). Results showed that the strain could grow well, ferment sugar quickly in cane molasses. By fermenting this bacterium anaerobically at 37 °C for 36 h incubation in 5 °BX molasses when the fermenter’s pH was controlled at 6.0, ethanol yield reached 13.77 g/L, and carbohydrate utilization percentage was 78.60%. RT-qPCR results verified the strain preferentially ferment glucose and fructose of molasses to ethanol at the molecular level. In addition, the metabolism of sugars, especially fructose, would be inhibited by elevating acidity. Our findings support the theoretical basis for exploring Lactic acid bacteria as a starter culture for converting sugarcane molasses into ethanol.

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Effects of Ultrasound on Fermentation of Glucose to Ethanol by Saccharomyces cerevisiae

Fermentation ◽

10.3390/fermentation5010016 ◽

2019 ◽

Vol 5 (1) ◽

pp. 16 ◽

Cited By ~ 5

Author(s):

Luis Huezo ◽

Ajay Shah ◽

Frederick Michel

Keyword(s):

Saccharomyces Cerevisiae ◽

Mass Transfer ◽

Glucose Uptake ◽

Ethanol Production ◽

Ethanol Yield ◽

Biofuel Production ◽

Inhibitory Effects ◽

Negative Effects ◽

Intraparticle Mass Transfer ◽

Improve Mass Transfer

Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial and inhibitory effects. In this study, the effects of ultrasound on mass transfer limitations during fermentation were examined. Calculation of the external and intraparticle observable moduli under a range of conditions indicate that no external or intraparticle mass transfer limitations should exist for the mass transfer of glucose, ethanol, or carbon dioxide. Fermentations of glucose to ethanol using Saccharomyces cerevisiae were conducted at different ultrasound intensities to examine its effects on glucose uptake, ethanol production, and yeast population and viability. Four treatments were compared: direct ultrasound at intensities of 23 and 32 W/L, indirect ultrasound (1.4 W/L), and no-ultrasound. Direct and indirect ultrasound had negative effects on yeast performance and viability, and reduced the rates of glucose uptake and ethanol production. These results indicate that ultrasound during fermentation, at the levels applied, is inhibitory and not expected to improve mass transfer limitations.

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Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

Applied and Environmental Microbiology ◽

10.1128/aem.03666-13 ◽

2014 ◽

Vol 80 (8) ◽

pp. 2410-2416 ◽

Cited By ~ 65

Author(s):

Areen Banerjee ◽

Ching Leang ◽

Toshiyuki Ueki ◽

Kelly P. Nevin ◽

Derek R. Lovley

Keyword(s):

Ethanol Production ◽

Genetic Manipulation ◽

Electron Flow ◽

Model Organism ◽

Inducible Expression ◽

Carbon Flow ◽

Wild Type ◽

Content Type ◽

Microbial Electrosynthesis ◽

Clostridium Ljungdahlii

ABSTRACTThe development of tools for genetic manipulation ofClostridium ljungdahliihas increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox forC. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported forClostridium perfringens, was investigated. The plasmid pAH2, originally developed forC. perfringenswith agusAreporter gene, functioned as an effective lactose-inducible system inC. ljungdahlii. Lactose induction ofC. ljungdahliicontaining pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression ofadhE130-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression ofadhE1in a strain in whichadhE1and theadhE1homologadhE2had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression ofadhE2similarly failed to restore ethanol production, suggesting thatadhE1is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

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OPTIMIZATION OF BIOVANILLIN PRODUCTION OF LEMONGRASS LEAVES HYDROLYSATES THROUGH PHANEROCHAETE CHRYSOSPORIUM

Jurnal Teknologi ◽

10.11113/jt.v77.6905 ◽

2015 ◽

Vol 77 (31) ◽

Cited By ~ 2

Author(s):

Huszalina Hussin ◽

Madihah Md Salleh ◽

Chong Chun Siong ◽

Muhammad Abu Naser ◽

Suraini Abd- Aziz ◽

...

Keyword(s):

Ferulic Acid ◽

Nitrogen Source ◽

Phanerochaete Chrysosporium ◽

Organic Nitrogen ◽

Nitrogen Sources ◽

Optimum Conditions ◽

Molar Yield ◽

Primary Screening ◽

Organic Nitrogen Source ◽

Inorganic And Organic Nitrogen

The recent study has demonstrated the effects of different nitrogen sources on vanillin production by Phanerochaete chrysosporium. Primary screening supported maximum biotransformation of ferulic acid (from lemongrass leaves hydrolysate) to vanillin by using ammonium chloride and yeast extract as inorganic and organic nitrogen source, respectively. With the 2-level factorial analysis, the optimum conditions of vanillin production from ferulic acid by P. chrysosporium was achieved at 0.192g/L with a molar yield of 24.5%.

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