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Industrial Yeast Strain (industrial + yeast_strain)
Selected AbstractsEffect of acetic acid and pH on the cofermentation of glucose and xylose to ethanol by a genetically engineered strain of Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 4 2010Elizabeth Casey Abstract A current challenge of the cellulosic ethanol industry is the effect of inhibitors present in biomass hydrolysates. Acetic acid is an example of one such inhibitor that is released during the pretreatment of hemicellulose. This study examined the effect of acetic acid on the cofermentation of glucose and xylose under controlled pH conditions by Saccharomyces cerevisiae 424A(LNH-ST), a genetically engineered industrial yeast strain. Acetic acid concentrations of 7.5 and 15 g L,1, representing the range of concentrations expected in actual biomass hydrolysates, were tested under controlled pH conditions of 5, 5.5, and 6. The presence of acetic acid in the fermentation media led to a significant decrease in the observed maximum cell biomass concentration. Glucose- and xylose-specific consumption rates decreased as the acetic acid concentration increased, with the inhibitory effect being more severe for xylose consumption. The ethanol production rates also decreased when acetic acid was present, but ethanol metabolic yields increased under the same conditions. The results also revealed that the inhibitory effect of acetic acid could be reduced by increasing media pH, thus confirming that the undissociated form of acetic acid is the inhibitory form of the molecule. [source] Physiological and molecular analysis of the stress response of Saccharomyces cerevisiae imposed by strong inorganic acid with implication to industrial fermentationsJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2010H.F. De Melo Abstract Aims:, This work aimed to identify the molecular mechanism that allows yeast cells to survive at low pH environments such as those of bioethanol fermentation. Methods and Results:, The industrial strain JP1 cells grown at pH 2 was evaluated by microarray analysis showing that most of the genes induced at low pH were part of the general stress response (GSR). Further, an acid-tolerant yeast mutant was isolated by adaptive selection that was prone to grow at low pH in inorganic but weak organic acid. It showed higher viability under acid-temperature synergistic treatment. However, it was deficient in some physiological aspects that are associated with defects in protein kinase A (PKA) pathway. Microarray analysis showed the induction of genes involved in inhibition of RNA and protein synthesis. Conclusions:, The results point out that low pH activates GSR, mainly heat shock response, that is important for long-term cell survival and suggest that a fine regulatory PKA-dependent mechanism that might affect cell cycle in order to acquire tolerance to acid environment. Significance and Impact of the Study:, These findings might guide the construction of a high-fermentative stress-tolerant industrial yeast strain that can be used in complex industrial fermentation processes. [source] Efficient use of DNA molecular markers to construct industrial yeast strainsFEMS YEAST RESEARCH, Issue 8 2007Philippe Marullo Abstract Saccharomyces cerevisiae yeast strains exhibit a huge genotypic and phenotypic diversity. Breeding strategies taking advantage of these characteristics would contribute greatly to improving industrial yeasts. Here we mapped and introgressed chromosomal regions controlling industrial yeast properties, such as hydrogen sulphide production, phenolic off-flavor and a kinetic trait (lag phase duration). Two parent strains derived from industrial isolates used in winemaking and which exhibited significant quantitative differences in these traits were crossed and their progeny (50,170 clones) was analyzed for the segregation of these traits. Forty-eight segregants were genotyped at 2212 marker positions using DNA microarrays and one significant locus was mapped for each trait. To exploit these loci, an introgression approach was supervised by molecular markers monitoring using PCR/RFLP. Five successive backcrosses between an elite strain and appropriate segregants were sufficient to improve three trait values. Microarray-based genotyping confirmed that over 95% of the elite strain genome was recovered by this methodology. Moreover, karyotype patterns, mtDNA and tetrad analysis showed some genomic rearrangements during the introgression procedure. [source] Effect of overexpression of transcription factors on the fermentation properties of Saccharomyces cerevisiae industrial strainsLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2009L. Hou Abstract Aims:, To investigate the effect of modulation of transcription factors on the fermentation properties of Saccharomyces cerevisiae industrial strains and to evaluate whether overexpression and co-overexpression of transcription factors would result in higher ethanol yield. Methods and Results:, A mutant gene spt15 (Phe177Ser, Tyr195His, Lys218Arg) was constructed by polymerase chain reaction mediated site-directed mutagenesis. The fermentation properties of the engineered strains in very high gravity fermentations were investigated. It is found that overexpression of SPT3 can enhance the resistance to ethanol and osmotic stress. On the contrary, overexpression of SPT15 or spt15 cannot obviously improve osmotic and ethanol tolerance of industrial strains. Additionally, simultaneous overexpression of SPT15 and SPT3 can not only distinctly enhance the resistance to ethanol and osmotic stress, but also improve fermentation performance. Conclusions:, Simultaneous modulation of the expression level of SPT15 and SPT3 can increase the production of ethanol by improving osmotic tolerance and ethanol tolerance of industrial strains. Significance and Impact of the Study:, Modulation of transcription factors provides a route to fermentation phenotypes of industrial yeast strains that are not readily accessible by traditional methods. [source] | ||||||||||