Project description:The main objective is to improve xylose fermentation by deletion of PHO80 gene in recombinant xylose-fermenting yeast strains. Microarray analysis was performed to investigate effects of PHO80 deletion on the gene expression profile of xylose-fermenting strains.
Project description:The main objective is to improve xylose fermentation by deletion of PHO13 gene in Xylose isomerase (XI) harboring yeast strains. Microarray analysis was performed to investigate effects of PHO13 deletion on the gene expression prolife of xylose-fermenting strains.
Project description:The main objective is to improve xylose fermentation by deletion of PHO80 gene in recombinant xylose-fermenting yeast strains. Microarray analysis was performed to investigate effects of PHO80 deletion on the gene expression profile of xylose-fermenting strains. Samples for 2 strains (wild-type control, PHO80-deleted strain) were taken after 6h of xylose fermentation. Each sample was triplicated, resulting in a total of 6 samples.
Project description:Creating Saccharomyces yeasts capable of efficient fermentation of pentoses such as xylose remains a key challenge in the production of ethanol from lignocellulosic biomass. Metabolic engineering of industrial Saccharomyces cerevisiae strains has yielded xylose-fermenting strains, but these strains have not yet achieved industrial viability due largely to xylose fermentation being prohibitively slower than that of glucose. Recently, it has been shown that naturally occurring xylose-utilizing Saccharomyces species exist. Uncovering the genetic architecture of such strains will shed further light on xylose metabolism, suggesting additional engineering approaches or possibly even the development of xylose-fermenting yeasts that are not genetically modified. We previously identified a hybrid yeast strain, the genome of which is largely Saccharomyces uvarum, which has the ability to grow on xylose as the sole carbon source. Despite the sterility of this hybrid strain, we were able to develop novel methods to genetically characterize its xylose utilization phenotype, using bulk segregant analysis in conjunction with high-throughput sequencing. We found that its growth in xylose is governed by at least two genetic loci: one of the loci maps to a known xylose-pathway gene, a novel allele of the aldo-keto reductase gene GRE3, while a second locus maps to an allele of APJ1, a chaperonin gene not previously connected to xylose metabolism. Our work demonstrates that the power of sequencing combined with bulk segregant analysis can also be applied to a non-genetically-tractable hybrid strain that contains a complex, polygenic trait, and it identifies new avenues for metabolic engineering as well as for construction of non-genetically modified xylose-fermenting strains.
Project description:We previously reported that a recombinant Candida utilis strain expressing a Candida shehatae xylose reductase K275R/N277D, a C. shehatae xylitol dehydrogenase, and xylulokinase from Pichia stipitis produced ethanol from xylose. However, its productivity was low. In this study, metabolomic (CE-TOF MS) and transcriptomic (microarray) analyses were performed to characterize xylose metabolism by the engineered C. utilis and to identify key genetic changes contributing to efficient xylose utilization. Metabolomic analysis revealed that the xylose-fermenting strain accumulated more pentose phosphate pathway intermediates, more NADH, and more glycolytic intermediates upstream of glyceraldehyde 3-phosphate than wild-type. Transcriptomic analysis of the strain grown on xylose indicated a significant increase in expression of genes encoding tricarboxylic acid cycle enzymes, respiratory enzymes, and enzymes involved in ethanol oxidation. To decrease the NADH/NAD+ ratio and increase ethanol yield from the fermentation of xylose, ADH1 encoding NADH-dependent alcohol dehydrogenase was overexpressed. The resultant strain exhibited a 17% increase in ethanol production and a 22% decrease in xylitol accumulation relative to the control.
Project description:Increasing yeast robustness against biomass-derived inhibitors and insoluble solids is essential for the realization of a bio-based economy. The xylose-fermenting Saccharomyces cereivisiae F12 strain was subjected to an adaptive laboratory evolution experiment in the presence of these stressors. The resulting evolved strain exhibit better fermentation performance in terms of xylose consumption and ethanol yields than the parental strain. The overexpression of genes related to cell wall integrity and the stress response, together with the downregulation of protein synthesis and iron transport and homeostasis were highlighted as the major biological processes responsible for the improved phenotype.
Project description:The modification of the The modification of the tolerance of xylose-fermenting yeast is an urgent issue for improving ethanol production. In this study, multiple genes involving in superoxide dismutase, glutathione biosynthesis, NADPH regeneration and acetic acid degradation were overexpressed using stress-induced promoters, which is selected from the transcriptome data. Stress-induced promoters were used to realize the feedback control of the tolerant genes, which can ultimately improve the tolerance and ethanol production. We reported the stress-induced promoters for overexpressing tolerant genes and increasing yeast tolerance in a feedback manner
