scholarly journals Enhanced biofuel production through coupled acetic acid and xylose consumption by engineered yeast

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Na Wei ◽  
Josh Quarterman ◽  
Soo Rin Kim ◽  
Jamie H.D. Cate ◽  
Yong-Su Jin
Keyword(s):  
Acetic Acid ◽  
Biofuel Production ◽  
Xylose Consumption ◽  
Engineered Yeast

scholarly journals Improved Acetic Acid Resistance in Saccharomyces cerevisiae by Overexpression of theWHI2Gene Identified through Inverse Metabolic Engineering

2016 ◽  
Vol 82 (7) ◽  
pp. 2156-2166 ◽  
Author(s):  
Yingying Chen ◽  
Lisa Stabryla ◽  
Na Wei
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Acetic Acid ◽  
Metabolic Engineering ◽  
Acid Stress ◽  
Acid Resistance ◽  
Biofuel Production ◽  
Gene Target ◽  
Content Type ◽  
Inverse Metabolic Engineering ◽  
Acetic Acid Resistance

ABSTRACTDevelopment of acetic acid-resistantSaccharomyces cerevisiaeis important for economically viable production of biofuels from lignocellulosic biomass, but the goal remains a critical challenge due to limited information on effective genetic perturbation targets for improving acetic acid resistance in the yeast. This study employed a genomic-library-based inverse metabolic engineering approach to successfully identify a novel gene target,WHI2(encoding a cytoplasmatic globular scaffold protein), which elicited improved acetic acid resistance inS. cerevisiae. Overexpression ofWHI2significantly improved glucose and/or xylose fermentation under acetic acid stress in engineered yeast. TheWHI2-overexpressing strain had 5-times-higher specific ethanol productivity than the control in glucose fermentation with acetic acid. Analysis of the expression ofWHI2gene products (including protein and transcript) determined that acetic acid induced endogenous expression of Whi2 inS. cerevisiae. Meanwhile, thewhi2Δ mutant strain had substantially higher susceptibility to acetic acid than the wild type, suggesting the important role of Whi2 in the acetic acid response inS. cerevisiae. Additionally, overexpression ofWHI2and of a cognate phosphatase gene,PSR1, had a synergistic effect in improving acetic acid resistance, suggesting that Whi2 might function in combination with Psr1 to elicit the acetic acid resistance mechanism. These results improve our understanding of the yeast response to acetic acid stress and provide a new strategy to breed acetic acid-resistant yeast strains for renewable biofuel production.

scholarly journals Improving Xylose Fermentation in Saccharomyces cerevisiae by Expressing Nuclear-Localized Hexokinase 2

2020 ◽  
Vol 8 (6) ◽  
pp. 856 ◽  
Author(s):  
Liyuan Zheng ◽  
Shan Wei ◽  
Meiling Wu ◽  
Xuehao Zhu ◽  
Xiaoming Bao ◽  
...  
Keyword(s):  
Glucose Sensor ◽  
Rna Binding ◽  
Xylose Fermentation ◽  
Rna Binding Proteins ◽  
Ethanol Yield ◽  
Xylose Utilization ◽  
Hexokinase 2 ◽  
Xylose Consumption ◽  
Glucose Signaling ◽  
Engineered Yeast

Understanding the relationship between xylose and the metabolic regulatory systems is a prerequisite to enhance xylose utilization in recombinant S. cerevisiae strains. Hexokinase 2 (Hxk2p) is an intracellular glucose sensor that localizes to the cytoplasm or the nucleus depending on the carbon source. Hxk2p interacts with Mig1p to regulate gene transcription in the nucleus. Here, we investigated the effect of nucleus-localized Hxk2p and Mig1p on xylose fermentation. The results show that the expression of HXK2S14A, which encodes a constitutively nucleus-localized Hxk2p, increased the xylose consumption rate, the ethanol production rate, and the ethanol yield of the engineered yeast strain by 23.5%, 78.6% and 42.6%, respectively. The deletion of MIG1 decreased xylose utilization and eliminated the positive effect of Hxk2p. We then performed RNA-seq and found that the targets of Hxk2pS14A on xylose were mainly genes that encode RNA-binding proteins. This is very different from the known targets of Mig1p and supports the notion that the Hxk2p-Mig1p interaction is abolished in the presence of xylose. These results will improve our understanding of the interrelation between the Snf1p-Mig1p-Hxk2p glucose signaling pathway and xylose utilization in S. cerevisiae and suggests that the expression of HXK2S14A could be a viable strategy to improve xylose utilization.

scholarly journals Improving Acetic Acid and Furfural Resistance of Xylose-Fermenting Saccharomyces cerevisiae Strains by Regulating Novel Transcription Factors Revealed via Comparative Transcriptomic Analysis

2021 ◽  
Vol 87 (10) ◽  
Author(s):  
Bo Li ◽  
Li Wang ◽  
Ya-Jing Wu ◽  
Zi-Yuan Xia ◽  
Bai-Xue Yang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Acetic Acid ◽  
Transcription Factors ◽  
Ethanol Yield ◽  
Regulation Mechanism ◽  
Lignocellulosic Hydrolysate ◽  
Inhibitor Tolerance ◽  
Xylose Consumption ◽  
Content Type ◽  
Beneficial Effects

ABSTRACT Acetic acid and furfural are the two prevalent inhibitors coexisting with glucose and xylose in lignocellulosic hydrolysate. The transcriptional regulations of Saccharomyces cerevisiae in response to acetic acid (Aa), furfural (Fur), and the mixture of acetic acid and furfural (Aa_Fur) were revealed during mixed glucose and xylose fermentation. Carbohydrate metabolism pathways were significantly enriched in response to Aa, while pathways of xenobiotic biodegradation and metabolism were significantly enriched in response to Fur. In addition to these pathways, other pathways were activated in response to Aa_Fur, i.e., cofactor and vitamin metabolism and lipid metabolism. Overexpression of Haa1p or Tye7p improved xylose consumption rates by nearly 50%, while the ethanol yield was enhanced by nearly 8% under acetic acid and furfural stress conditions. Co-overexpression of Haa1p and Tye7p resulted in a 59% increase in xylose consumption rate and a 12% increase in ethanol yield, revealing the beneficial effects of Haa1p and Tye7p on improving the tolerance of yeast to mixed acetic acid and furfural. IMPORTANCE Inhibitor tolerance is essential for S. cerevisiae when fermenting lignocellulosic hydrolysate with various inhibitors, including weak acids, furans, and phenols. The details regarding how xylose-fermenting S. cerevisiae strains respond to multiple inhibitors during fermenting mixed glucose and xylose are still unknown. This study revealed the transcriptional regulation mechanism of an industrial xylose-fermenting S. cerevisiae strain in response to acetic acid and furfural. The transcription factor Haa1p was found to be involved in both acetic acid and furfural tolerance. In addition to Haa1p, four other transcription factors, Hap4p, Yox1p, Tye7p, and Mga1p, were identified as able to improve the resistance of yeast to these two inhibitors. This study underscores the feasibility of uncovering effective transcription factors for constructing robust strains for lignocellulosic bioethanol production.

scholarly journals Quantitative assay of Indole Acetic Acid-producing bacteria isolated from several lakes in East Java, Indonesia

2020 ◽  
Vol 21 (11) ◽  
Author(s):  
Sulistya Ika Ramadhani Sulistya ◽  
Sitoresmi Prabaningtyas Sitoresmi ◽  
Agung Witjoro Agung ◽  
Rina Triturani Saptawati Rina ◽  
Achmad Rodiansyah Achmad
Keyword(s):  
Acetic Acid ◽  
Indole Acetic Acid ◽  
Fossil Fuels ◽  
Morphological Characterization ◽  
Biofuel Production ◽  
Quantitative Assay ◽  
Phenotypic Characterization ◽  
Bacterial Isolates ◽  
Acid Producing Bacteria

Abstract. Ramadhani SI, Prabaningtyas S, Witjoro A, Saptawati TR, Rodiansyah A. 2020. Quantitative assay of Indole Acetic Acid-producing bacteria isolated from several lakes in East Java, Indonesia. Biodiversitas 21: 5448-5454. Biofuel is an alternative to fossil fuels that are environmentally friendly with low emissions. Biofuel from biomass microalgae, especially Chlorella vulgaris, has an essential role in biofuel production. Increasing biomass microalgae was done by co-culture between microalgae and bacteria. This research aims to determine the potential of bacterial isolates to produce the IAA hormone and identify the highest isolate with the ability to synthesis IAA from four lakes in East Java. This research was conducted by culturing bacterial isolates in the Tryptic Soy Broth (TSB) to add tryptophan media in various periods of incubation. The absorbance was measured with UV-Vis spectrophotometry at a wavelength of 530 nm for determining IAA-production from bacterial isolates. The results showed that the "12" code bacterial isolate from Ranu Grati produced the highest IAA hormone concentration, with an average of 30.23 ppm. The morphological characterization of the highest IAA-producing bacteria showed that isolate included the Enterobacteriaceae group and phenotypic characterization include Enterobacter cloacae complex (ECC).

scholarly journals Application of metabolic controls for the maximization of lipid production in semicontinuous fermentation

2017 ◽  
Vol 114 (27) ◽  
pp. E5308-E5316 ◽  
Author(s):  
Jingyang Xu ◽  
Nian Liu ◽  
Kangjian Qiao ◽  
Sebastian Vogg ◽  
Gregory Stephanopoulos
Keyword(s):  
Acetic Acid ◽  
Low Cost ◽  
Lipid Production ◽  
Environmental Benefits ◽  
Biofuel Production ◽  
Carbon Substrate ◽  
Microbial Conversion ◽  
Cell Recycling ◽  
Semicontinuous Fermentation ◽  
High Density Cell

Acetic acid can be generated through syngas fermentation, lignocellulosic biomass degradation, and organic waste anaerobic digestion. Microbial conversion of acetate into triacylglycerols for biofuel production has many advantages, including low-cost or even negative-cost feedstock and environmental benefits. The main issue stems from the dilute nature of acetate produced in such systems, which is costly to be processed on an industrial scale. To tackle this problem, we established an efficient bioprocess for converting dilute acetate into lipids, using the oleaginous yeast Yarrowia lipolytica in a semicontinuous system. The implemented design used low-strength acetic acid in both salt and acid forms as carbon substrate and a cross-filtration module for cell recycling. Feed controls for acetic acid and nitrogen based on metabolic models and online measurement of the respiratory quotient were used. The optimized process was able to sustain high-density cell culture using acetic acid of only 3% and achieved a lipid titer, yield, and productivity of 115 g/L, 0.16 g/g, and 0.8 g⋅L−1⋅h−1, respectively. No carbon substrate was detected in the effluent stream, indicating complete utilization of acetate. These results represent a more than twofold increase in lipid production metrics compared with the current best-performing results using concentrated acetic acid as carbon feed.

scholarly journals Engineering of Saccharomyces cerevisiae for efficient fermentation of cellulose

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Eun Joong Oh ◽  
Yong-Su Jin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lignocellulosic Biomass ◽  
Biofuel Production ◽  
Cellulolytic Enzymes ◽  
Microbial Conversion ◽  
Biomass Hydrolysis ◽  
Yeast Strains ◽  
Attractive Option ◽  
Engineered Yeast ◽  
Efficient Fermentation

ABSTRACT Conversion of lignocellulosic biomass to biofuels using microbial fermentation is an attractive option to substitute petroleum-based production economically and sustainably. The substantial efforts to design yeast strains for biomass hydrolysis have led to industrially applicable biological routes. Saccharomyces cerevisiae is a robust microbial platform widely used in biofuel production, based on its amenability to systems and synthetic biology tools. The critical challenges for the efficient microbial conversion of lignocellulosic biomass by engineered S. cerevisiae include heterologous expression of cellulolytic enzymes, co-fermentation of hexose and pentose sugars, and robustness against various stresses. Scientists developed many engineering strategies for cellulolytic S. cerevisiae strains, bringing the application of consolidated bioprocess at an industrial scale. Recent advances in the development and implementation of engineered yeast strains capable of assimilating lignocellulose will be reviewed.

scholarly journals Simulating Extracellular Glucose Signals Enhances Xylose Metabolism in Recombinant Saccharomyces cerevisiae

2020 ◽  
Vol 8 (1) ◽  
pp. 100 ◽  
Author(s):  
Meiling Wu ◽  
Hongxing Li ◽  
Shan Wei ◽  
Hongyu Wu ◽  
Xianwei Wu ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Metabolic Networks ◽  
Glucose Sensing ◽  
Biofuel Production ◽  
Xylose Utilization ◽  
High Concentration ◽  
Xylose Metabolism ◽  
Camp Phosphodiesterase ◽  
Xylose Consumption ◽  
Recombinant Saccharomyces Cerevisiae

Efficient utilization of both glucose and xylose from lignocellulosic biomass would be economically beneficial for biofuel production. Recombinant Saccharomyces cerevisiae strains with essential genes and metabolic networks for xylose metabolism can ferment xylose; however, the efficiency of xylose fermentation is much lower than that of glucose, the preferred carbon source of yeast. Implications from our previous work suggest that activation of the glucose sensing system may benefit xylose metabolism. Here, we show that deleting cAMP phosphodiesterase genes PDE1 and PDE2 increased PKA activity of strains, and consequently, increased xylose utilization. Compared to the wild type strain, the specific xylose consumption rate (rxylose) of the pde1Δ pde2Δ mutant strains increased by 50%; the specific ethanol-producing rate (rethanol) of the strain increased by 70%. We also show that HXT1 and HXT2 transcription levels slightly increased when xylose was present. We also show that HXT1 and HXT2 transcription levels slightly increased when xylose was present. Deletion of either RGT2 or SNF3 reduced expression of HXT1 in strains cultured in 1 g L−1 xylose, which suggests that xylose can bind both Snf3 and Rgt2 and slightly alter their conformations. Deletion of SNF3 significantly weakened the expression of HXT2 in the yeast cultured in 40 g L−1 xylose, while deletion of RGT2 did not weaken expression of HXT2, suggesting that S. cerevisiae mainly depends on Snf3 to sense a high concentration of xylose (40 g L−1). Finally, we show that deletion of Rgt1, increased rxylose by 24% from that of the control. Our findings indicate how S. cerevisiae may respond to xylose and this study provides novel targets for further engineering of xylose-fermenting strains.

scholarly journals Identification of a glucose-insensitive variant of Gal2 from Saccharomyces cerevisiae exhibiting a high pentose transport capacity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sebastian A. Tamayo Rojas ◽  
Virginia Schadeweg ◽  
Ferdinand Kirchner ◽  
Eckhard Boles ◽  
Mislav Oreb
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Competitive Inhibition ◽  
Cellular Membrane ◽  
Major Constituent ◽  
Transport Capacity ◽  
Xylose Consumption ◽  
Fermentation Time ◽  
Renewable Feedstocks ◽  
Engineered Yeast ◽  
Pentose Transport

AbstractAs abundant carbohydrates in renewable feedstocks, such as pectin-rich and lignocellulosic hydrolysates, the pentoses arabinose and xylose are regarded as important substrates for production of biofuels and chemicals by engineered microbial hosts. Their efficient transport across the cellular membrane is a prerequisite for economically viable fermentation processes. Thus, there is a need for transporter variants exhibiting a high transport rate of pentoses, especially in the presence of glucose, another major constituent of biomass-based feedstocks. Here, we describe a variant of the galactose permease Gal2 from Saccharomyces cerevisiae (Gal2N376Y/M435I), which is fully insensitive to competitive inhibition by glucose, but, at the same time, exhibits an improved transport capacity for xylose compared to the wildtype protein. Due to this unique property, it significantly reduces the fermentation time of a diploid industrial yeast strain engineered for efficient xylose consumption in mixed glucose/xylose media. When the N376Y/M435I mutations are introduced into a Gal2 variant resistant to glucose-induced degradation, the time necessary for the complete consumption of xylose is reduced by approximately 40%. Moreover, Gal2N376Y/M435I confers improved growth of engineered yeast on arabinose. Therefore, it is a valuable addition to the toolbox necessary for valorization of complex carbohydrate mixtures.

scholarly journals Improving Saccharification of Oil Palm Shell by Acetic Acid Pretreatment for Biofuel Production

2017 ◽  
Vol 141 ◽  
pp. 146-149 ◽  
Author(s):  
Kittipong Rattanaporn ◽  
Supacharee Roddecha ◽  
Malinee Sriariyanun ◽  
Kraipat Cheenkachorn
Keyword(s):  
Acetic Acid ◽  
Oil Palm ◽  
Biofuel Production ◽  
Acid Pretreatment ◽  
Palm Shell ◽  
Oil Palm Shell
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