EBI Personnel Directory Jin, Yong-Su
This program addresses issues in developing optimal microbial strains for producing cellulosic biofuels: efficient fermentation of the mixed sugars present in cellulosic hydrolysates under the presence of fermentation inbitors. Cellulosic biomass mainly consists of two major sugars (glucose and xylose) but there is no optimal microorganism which has the capacity of fermenting xylose as well as glucose with high yield and productivity. Also, the generation of inhibitory compounds during pretreatment processes of biomass is one of the major barriers impeding the commercialization of biofuels from cellulosic biomass. The goal of the program is to develop engineered yeast strains capable of simultaneously fermenting mixed sugars (glucose, cellodextrin, and xylose) under the presence of fermentation inhibitors in lignocellulosic hydrolysates. Genetic/genomics tools for engineering industrial yeast strains and genetic bases of desirable traits are being generated.
The research in this project aimed to improve efficiency (yield) and rate (productivity) of xylose fermentation by recombinant S. cerevisiae. Previous studies suggested that simultaneous perturbation of multiple genes might be required in order to facilitate high yield/productivity xylose fermentation by recombinant S. cerevisiae. However, such a set of gene targets enhancing xylose fermentation has not been known. This research contributed to the development of ethanol fermentation processes that will help make biofuel production economically viable.
This project builds on a past study that developed an efficient xylose-fermenting yeast strain. However, the engineered strain could not ferment cellulosic sugars (glucose and xylose) simultaneously due to glucose repression of xylose. In this project, several yeast metabolic engineering approaches are used in an effort to overcome the inhibition mechanism, allowing co-fermentation of glucose and xylose. Industrial applications of the co-fermentation system are also demonstrated.