A number of reports have been published on the pre-treatment and enzymatic hydrolysis of the lignocellulosic biomass 14 and 15. The previous approaches were mainly focused on selecting S. cerevisiae isolates that are tolerant to a single stress at a time 16 and 17. However, recently, a few reports have considered natural isolates for industrial adaptation based on their innate resistance and fermentation performance in the presence of two or more simultaneous stresses 18, 19, 20 and 21. Because the combined effect of inhibitors, high temperature and concentrated ethanol poses a major challenge for the successful production of bioethanol, selecting natural S. cerevisiae isolates with inherent resistance to these stress factors could be a more realistic strategy for second-generation biofuel production (22).
To select promising S. cerevisiae strains to serve as a platform for second-generation biofuel production, natural yeast isolates that were derived from grape wine and medicinal herbs from different regions of India were screened. The growth and fermentation performance of these isolates was evaluated in the presence of various stresses that are encountered during lignocellulosic hydrolysate fermentation. In addition, the fermentation performance of the selected isolates for ethanol production, using wheat and rice straw cellulosic hydrolysates, was evaluated.