Development of Platform Yeast Strain Capable of Direct Fermentation of Raw Biomass to Ethanol

Lignocellulosic biomass, particularly from agricultural and forestry sectors, represents a rather unused low-cost source for production of biofuel (alkanes and fatty alcohols), commodity chemicals (waxes), fine chemicals (sesquiterpenes, bioplastics) and proteins (enzymes, pharmaceuticals). To convert them into such products, the presence of the robust microbial platform is required. However, significant challenges exist for the efficient cost-effective conversion of biomass to such materials. One technical barrier for biomass conversion is the stress condition caused by toxic compounds released from the chemical pretreatment process or the enzymatic digestion of biomass in which remarkably interfere with microbial growth and subsequent fermentation. We believe they are many broad yeast candidates available in nature, which can move beyond difficulties to out boundary so that the good platform for fermentation of lignocellulosic biomass could be built without too much genetic modification. However, the selection of appropriate candidates is not easy due to the unique adaptation possessed by many yeasts upon the environmental stress. The intensive screening should be conducted using natural resources, such as soil, leaf, fermented foods. However, to screen across such a wide range of resources requires arduous, cost- and time-consuming processes as well as knowledges. In this study, we have developed rapid method for screening the candidate yeasts from huge number of yeast strains deposited in NITE Biological Resource Center (NBRC) and also in Indonesia Culture Collection (InaCC), which capable of direct fermentation of lignocellulosic sugar lysate into ethanol. By screening of more than 3000 yeast strains, we found some potential candidates for rapid fermentation of sugars, from the lignocellulosic sugar lysate and also from the synthetic medium containing high concentrated inhibitory chemical cocktails. Most of yeasts screened as candidate strains are belong to Saccharomyces cerevisiae with specific phenotypes such as high-temperature adaptive, flocculation and rapid invasive growth.