Torulaspora quercuum shows great potential for bioethanol production from macroalgal hydrolysate

Abstract

Yeast fermenting galactose (Gal) to ethanol are key to develop bioethanol production from galactan-rich red algal feedstock. To improve Gal-based bioethanol production, the potential of non-Saccharomyces yeast was investigated with screening Gal-fermenting yeast from environment in this study. Isolates, Torulaspora quercuum strains KRT82 and KRT85 were successfully effectively produced 54.77 ± 2.18 and 59.92 ± 2.18 g L−1 ethanol, respectively, from 200 g L−1 Gal as the carbon source in modified yeast–malt broth. The ethanol yield reached nearly corresponding to the theoretical yield. The isolates produced 8–10 g L−1 ethanol from Gelidiaceae hydrolysate containing approximately 20 g L−1 Gal and 10–13 g L−1 glucose, with an ethanol yield of 54%–57%. The cells flocculated. During repeated batch fermentation, the ethanol yield were reached to 38 g L−1-working volume for 39 h, and the productivity of ethanol reached 0.98 g L−1 working volume h−1.