Improving Yeast Strain Robustness for Biorefinery Applications

Interest in oil-based biochemical and biofuel production processes has increased because of increasing energy demand coupled with the rising concern of global warming. In the last decade, microbial biofuel production through economical bioprocesses has shown a high potential as an alternative to conventional ways of fuel production. The upstream processing includes the producer microorganism, which is the selection of a suitable microorganism in the preliminary phase of the fermentation. Wheat straw hydrolysate (WSH) is a type of lignocellulosic hydrolysate derived from wheat straw, an agricultural residue. It is abundant in renewable agricultural byproducts and potentially an excellent sustainable feedstock for biofuel and biochemical production. However, in WSH, several inhibitory compounds exist, hence demanding the development of more robust microbial strains that can tolerate the respective stressors and efficiently convert the sugars into the respective final product.

This study indicated that the five Saccharomyces cerevisiae grew similarly in wheat straw hydrolysate under anaerobic conditions but had extreme differences in transcriptional stress response. 

The chosen strains allowed the differentially expressed genes to be directly compared under aerobic conditions in WSH without interference from physiology-driven confounding variables. However, it was the case that the activities of the different strains were very similar in growth pattern.

The key observations of this study were higher expression of genes related to glutathione metabolism, iron homeostasis, and membrane biosynthesis in wildtype isolates; some sugar transporter genes that were highly expressed in LBCM strains might reflect variation in evolutionary adaptations relative to the tolerance toward hydrolysate. The study provides insights into genetic targets for improving yeast strain robustness for biorefinery applications.