Isolation and identification of non-saccharomyces ethanol and thermo-tolerant yeasts strains from fermented carbohydrate wastes

Abstract

Ethanol is an important chemical with its potential as a biofuel to displace the environmentally unfriendly fossil fuels. Isolation and identification of ethanol and thermo-tolerant yeast capable of producing ethanol were carried out in this study. Seventy (70) samples from different fermented foods and agricultural wastes from millets, sorghum, maize, rice and guinea corn were obtained from local sellers in Panteka, Farin-Gida, Barkallahu and Barnawa in Kaduna State (North West), Nigeria were used in this research. The samples were collected using a sterile plastic container and were transported immediately to the Biotechnology laboratory of the Nigerian Defence Academy in iced chamber.

They were serially diluted in distilled water and inoculated on yeast extract peptone dextrose agar (YEPD) media plates supplemented with 0.2% chloramphenicol. The plates were incubated at 30°C for 72 hours and developed colonies were sub-cultured to obtain pure culture which was observed for their morphological and microscopic characteristics. After examination, ten (10) yeast isolates were obtained from the seventy (70) samples collected. Flocculation test, Hydrogen sulphide test, preliminary alcohol production and sugar fermentation test were carried out on the isolates and their tolerance to ethanol at varying concentration 5%-20% (v/v) and temperature at 37^oC-45^oC were studied. Using the internal transcribed spacer (ITS) 1 and 2 regions primer, the DNA were sequenced and the isolates identified. Four isolates FG 17, FG 27, P1 and BN50 showed ethanol tolerance potentials at 20% ethanol and were identified as strains of Diutina rugosa, Candida sp, Candida ethanolica and Candida tropicalis while one isolate FG 35 showed good thermo-tolerance ability at 45^oC and was identified as Trichosporon sp.