Technological properties and sugar tolerance performance of palm wine yeasts isolated from parts of Nsukka, Nigeria

The ability of yeasts to survive and produce significant ethanol in high sugar medium and high ethanol environment is essential for the use of such yeasts in industrial and edible ethanol production. Four Saccharomyces spp. strains () isolated from palm wine and an industrial strain were studied in high glucose medium for ethanol production and ability to survive in high sugar medium. Saccharomyces cerevisiae  produced remarkable cell concentration relative to other isolates and the industrial strain, IR-2 in 16, 24 and 36% (w/v glucose) fermentation broth. S. cerevisiae survived well with good biomass yields of 2.21 and 6.74 fold in 24 and 36% w/v glucose broth, respectively. Ethanol fermentation at glucose concentration of 40% (w/v) produced 42.45 g ethanol concentration (P), 0.387g L-1h-1 volumetric productivity (Qp) and a yield (Yps) of 0.329 gg-1. The sugar tolerance property was observed in a fermentation broth with an initial pH of 5.8. Additionally, S. cerevisiae strain was adaptive to 10% ethanol in 24% glucose solution. The yield obtained and properties exhibited by this isolate compares outstandingly with published data for a range of industrially important isolates; thus, this isolate could be used to produce bioethanol in industrially sustainable processes.   Key words: Saccharomyces, bioethanol, osmotic stress, ethanol tolerance, sugar tolerance, indigenous yeast.