Lignocellulosic bioethanol production employing newly isolated inhibitor and thermotolerant Saccharomyces cerevisiae DBTIOC S24 strain in SSF and SHF

Abstract

Bioethanol is a renewable alternative to fossil fuels which facilitate energy security and reduce greenhouse-gas emissions. High gravity fermentation employing a thermo and inhibitor tolerant strain is a promising technology to reduce fermentation time as well as cost. The present study investigates lignocellulosic ethanol production using inhibitor and thermotolerant S. cerevisiae DBTIOC S24 from non-detoxified and unsterilized rice straw hydrolysate. Efficient ethanol production was observed at a wide range of pH (3–7) and temperature (25–42 °C) using S. cerevisiae isolate. In the presence of lignocellulosic derived inhibitors, a maximum of 75.33 g L⁻¹ (85.56%) and 73.30 g L⁻¹ (79.93%) ethanol was produced at 30 °C and 42 °C, respectively. During fermentation, pH plays an important role in overcoming the synergistic effect of inhibitors. More than 80.65% and 73.5% ethanol yield was achieved employing this isolate with high solid loading (20%) and 20 FPU g⁻¹ of solid loading via simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), respectively. While, 91% ethanol yield was obtained during fermentation using rice enzymatic hydrolysate. These values are comparable to the best results reported. Therefore, this isolate has great potential due to its inhibitor and thermotolerant characteristics for lignocellulosic ethanol production at the industrial scale with a lower process time and cost.