Isolation and Screening of Yeast Isolates Indigenous Palm Wine for Ethanol Production
Ukponobong E. Antia1*, Otobong D. Akan1, Nsikak U. Stephen1,
Cheryl K. Eno-Ibanga1, and Nseobong G. Akpan2
1Department of Biological Sciences, Akwa Ibom State University, Nigeria
2Department of Medical Microbiology and Parasitology,
University of Uyo Teaching Hospital, Uyo, Nigeria.
The problem that has been ravaging ethanol producing industries for decades now is the ability of industrial yeast isolates to withstand ethanol production stress conditions while giving out optimal ethanol yeast. Hence, there is need to constantly source for yeast isolates with these qualities. Yeast isolates obtained from aging palm-wine were investigated for their ability to withstand some ethanol production stress conditions. Their growth responses were observed qualitatively at different temperatures, sugar concentrations (up to 200 g/L), and ethanol concentration (up to 20% v/v). A total of 20 yeast isolates were obtained and screened for ethanol stress condition tolerance. Saccharomyces cerevisiae SCPW 17 was able to tolerate ethanol production stress conditions with minimal growth at 45°C and 20% v/v ethanol and intensive growth in a medium containing 200 g glucose/L. The identity of S. cerevisiae SCPW 17 was determined and confirmed by the analysis of its internal transcribed spacer (ITS1) region of the 18S ribosomal DNA. Saccharomyces cerevisiae SCPW 17 exhibited good characteristics needed in yeast isolates meant for ethanol and bio-ethanol production.
Yeasts are very important in ethanol production through the fermentation of varieties of sugars. They are fungi found as members of the group ascomycetes and basidiomycetes. They have a unique in their budding and fission mode of reproduction (Boekhout & Kurtzman 1996).
Yeasts such as S. cerevisiae have been used in alcohol production, especially in the brewery and wine industries, for thousands of years. Obvious reasons being that this yeast gives high ethanol yield (90% theoretical yield), high ethanol productivity, and has a profound ability to withstand high ethanol concentration up to 40 g/L ethanol in the production milieu (Nigam & Singh 2011).
Nowadays, yeasts generally have used to produce bio-ethanol from renewable energy sources. Yeast strains such as Pichia stipitis, S. cerevisiae, and Kluyveromyces fagilis have been reported as good ethanol producers from various simple sugars types (Mussato et al. 2012; Azhar, et al. 2017). S. cerevisiae is ‘generally regarded as safe’ (GRAS) for use in industrial ethanol production for several applications. It tolerates a wide range of pH, which makes it less susceptible to contamination during fermentation. . . . . . read more
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