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.

Evaluation of divergent yeast genera for fermentation-associated stresses and identification of a robust sugarcane distillery waste isolate Saccharomyces cerevisiae NGY10 for lignocellulosic ethanol production in SHF and SSF

“…Notably, acid-pretreated RS with pre-saccharification produced maximum ethanol of 30.22 g/l with the efficiency of 86.43% in SSF. To the best of our knowledge, it was higher than the other recently published reports involving SSF processes, including 70.7% [46], 56.3% [47] and 80.65% [26] by employing S. cerevisiae isolates and 77.7% by employing K. marxianus isolate [48].

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“…Since cellulase exhibit maximum activity at 50 °C; hence, pre-saccharification at 50 °C for 6 h was performed in parallel before adding the yeast cells. As reported earlier, we expected that pre-saccharification will enhance the ethanol yield [8, 26, 45]. Without pre-saccharification, 5.0% w/v solid loading of untreated, acid- and alkali-pretreated RS produced 2.02 g/l, 17.36 g/l and 11.78 g/l ethanol, respectively.…”

“…Rise in temperature during fermentation reduces the efficiency of mesothermal yeast for ethanol production; therefore, fermentation performance at elevated temperatures is considered as an important characteristic for an industrial yeast. Additionally, thermotolerant yeast isolates are required for developing SSF technology to cope up with the thermal miss alliance optima of commercial cellulase activities and fermentation performances [26, 42]. Hence, we evaluated the fermentation performances at 30 °C, 40 °C and 42 °C, respectively.…”

“…Direct fermentation of LH is challenging due to the presence of a cocktail of inhibitors generated during pretreatment and hence in most of the cases, low ethanol yields and productivities have been reported [11, 26]. Additionally, optimum enzymatic hydrolysis occurs at 50 °C; hence, cooling to 30 °C for obtaining maximum ethanol production yield by yeast is another cost-ineffective step in lignocellulosic ethanol production.…”

“…In most of the previous studies, yeast species belonging to one or two genera were evaluated for thermotolerance, pre-treatment inhibitor tolerance and LH fermentations, simultaneously [4, 6, 26–28]. In this study, yeast isolates belonging to Saccharomyces , Kluyveromyces, Candida , Scheffersomyces, Ogatea and Wickerhamomyces genera were evaluated for fermentation performances at 40 °C along with the pretreatment generated inhibitors (furfural, 5-HMF and acetic acid) and fermentation stress-tolerant phenotypes.…”