Isolation, identification and screening of local yeast strains for attributes important for industrial ethanol production

                       Nwachukwu*,¹ I. K., Ewelike², C.N. and Ibekwe³, V. I

1. Microbiology Unit, Dept. of Laboratory Technology, Federal Polytechnic, Kaura Namoda, Zamfara State
        2. National Agency for Foods and Drugs, Admin and Control, Federal Secretariat, Port Harcourt, Rivers State
        3. Department of Industrial microbiology, Federal University of Technology, Owerri, Imo State 
            e-mail ikennatex @ yahoo.com

Abstract

Local yeast strains from fruits in Kaura Namoda, Zamfara State, Nigeria, were isolated, identified and tested for certain characteristics necessary for ethanol production.  The yeasts include six fully identified species and two unidentified species:  Hansenula anomala, Pichia ohmeri, Saccharomyces cerevisiae, Saccharomyces uvarum, Schizosaccharomyces pombe and Zygosaccharomyces fermentati.  The attributes important for ethanol production investigated include; ethanol production, ethanol tolerance, fermentation of simple sugars, flocculence and fermentation of other sugars.  Results revealed that none of the isolates could assimilate nitrogen as KNO₃.  None of the identified yeast strains could ferment arabinose, cellobiose, and ribose, while they all fermented mannose.  The flocculence assay showed that only S. cerevisiae, S.  uvarium and the unidentified yeast 1 could flocculate at; 1.60, 0.50 and 0.50ml/10mins respectively.  All the yeast isolates tolerated 10% (v/v) ethanol.  Only P. ohmeri and S. cerevisiae survived in 18% ethanol (v/v).  All the yeast isolates produced ethanol at 37⁰C using 10% (w/v) glucose within 48 hours.  No significant correlation existed between the quantity of ethanol produced and neither flocculation rate nor ethanol tolerance (p = 0.05).