Effect of inhibitors present n lignocellulosic hydrolysates on evolved xylose fermenting Saccharomyces cerevisiae strains

Conference poster, 2012

The development of inhibitor tolerant ethanologenic yeasts is one of the important challenges for a successful bioethanol production process from lignocellulose. Furthermore, an efficient microorganism for bioethanol production has to be able to ferment xylose together with glucose since xylose represents a large fraction in the lignocellulosic biomass. Weak acids and phenolic compounds are some of the prevalent inhibitors generated during pretreatment of lignocellulose and they will be present in the fermentation broth stressing the yeast affecting the fermentation performance. Although some studies on the effect of organic acids on fermenting microorganisms have been published, there is a lack of knowledge on the effect of phenolic compounds on yeast and more concretely about the effect on the xylose fermentation performance. In this study, the effect of acetic acid and vanillin on yeast growth on glucose and xylose will be elucidated using synthetic media mimicking lignocellulosic hydrolysates. It is known that one of general stress responses in yeast is the accumulation and mobilization of energy reserves (trehalose and glycogen). Trehalose protects cells from damage, increasing cell viability, however, when inhibitors are present in the media the trehalose synthesis and degradation could be affected. Furthermore differences in gene expression of key genes involved in acetic acid and vanillin tolerance and xylose fermentation will be studied. In this work we will also compare different evolved strains and evaluate mixed populations compared to single clones, in terms of trehalose and glycogen content and inhibitor tolerance.