Screening and Characterization of Ethanol-Producing Yeasts from Sewage Sludge, Soil and Rotten Fruits

Abstract

Food waste recycling attracts people's attention recently. Fiber such as vegetable stem vegetable is main ingredient of food waste. How to use this resource becomes an important topic. In this manuscript, six ethanol-producing yeasts were isolated from sewage sludge, soil and rotten fruits, then examined using PDA medium, TTC screening, and Duchenne tube fermentation experiments. After screeing on D-xylose medium, an ethanol-producing yeast Y9, Saccharomyces cerevisiae, was isolated. Ethanol production over time by strain Y9 indicated that 12 days is the screened strain's optimal fermentation time. The screened strain's specific growth rate is 0.12 h–1, and its ethanol productivity is higher than that of store-bought Angel Yeast or its co-culture, which indicated inhibition existing among the strains. Moreover, the ethanol productivity in shaken samples was higher than that in static samples, indicating that slight oxygen conditions benefited the screened strain's ethanol production. The results may have implications in ethanol production and the treatment of sewage sludge and food waste.