Abstract
Improving lactic acid (LA) tolerance is important for cost-effective microbial production of LA under acidic fermentation conditions. Previously, we generated LA-tolerant D-LA-producing S. cerevisiae strain JHY5310 by laboratory adaptive evolution of JHY5210. In this study, we performed whole genome sequencing of JHY5310, identifying four loss-of-function mutations in GSF2, SYN8, STM1, and SIF2 genes, which are responsible for the LA tolerance of JHY5310. Among the mutations, a nonsense mutation in GSF2 was identified as the major contributor to the improved LA tolerance and LA production in JHY5310. Deletion of GSF2 in the parental strain JHY5210 significantly improved glucose uptake and D-LA production levels, while derepressing glucose-repressed genes including genes involved in the respiratory pathway. Therefore, more efficient generation of ATP and NAD+ via respiration might rescue the growth defects of the LA-producing strain, where ATP depletion through extensive export of lactate and proton is one of major reasons for the impaired growth. Accordingly, alleviation of glucose repression by deleting MIG1 or HXK2 in JHY5210 also improved D-LA production. GSF2 deletion could be applied to various bioprocesses where increasing biomass yield or respiratory flux is desirable.
Highlights
Improving lactic acid (LA) tolerance is important for cost-effective microbial production of LA under acidic fermentation conditions
Saccharomyces cerevisiae having higher acid tolerance than lactic acid bacteria is considered a promising host for LA production[5,6,7,8,9]
We demonstrated that alleviating glucose repression by GSF2 deletion can significantly improve LA tolerance and LA production possibly by eliciting more efficient ATP synthesis via respiratory pathway
Summary
Improving lactic acid (LA) tolerance is important for cost-effective microbial production of LA under acidic fermentation conditions. Considering the fact that LA tolerance mechanisms are not fully understood and involve complex networks of multiple genes[15], adaptive laboratory evolution is another efficient strategy to obtain tolerant strains[19,20]. This can be a powerful tool in combination with whole genome sequencing analysis and reverse metabolic engineering for the identification of modified genes and pathways, which are difficult to predict rationally. We demonstrated that alleviating glucose repression by GSF2 deletion can significantly improve LA tolerance and LA production possibly by eliciting more efficient ATP synthesis via respiratory pathway
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
