Abstract

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Palm wine is the collective name for a group of alcoholic beverages produced by the natural fermentation by indigenous microorganisms of the sap obtained from various tropical plants of the Palmae family. The aim of this study was to determine the growth and physiological properties of yeast isolates from palm wine samples. Fifty (50) palm wine samples were aseptically collected in sterile bottles from different locations within Ikwuano Local Government Area of Abia State. The samples were cultured by spread plate method on Sabouraud Dextrose Agar and Glucose Yeast Agar. Four (4) yeasts: Saccharomyces cerevisiae, Saccharomyces globosus(top fermenters) and Saccharomyces carlsbergensis and Saccharomyces uvarum (bottom fermenters) were isolated. The four isolates were subjected to temperature, copper Sulphate (CuSo4), pH, ethanol, Sodium Metabisulfite tolerance and flocculation tests. Saccharomyces cerevisiae and uvarum were top fermenting while Saccharomyces carlsbergensis and globosus were bottom-fermenting. S. cerevisiae was found in all samples while S. uvarum had the least occurrence (40%). From the temperature tolerance test, S. cerevisiae, had the highest temperature tolerance (42oC) while S. uvarum recorded the least temperature tolerance (39oC). Some of the isolates demonstrated flocculation ability and were positive in fermentative and assimilation test for some sugars. Three of the yeast isolates grew slightly at pH 2.0 while S. uvarumdid not grow at pH 2.0. All the yeasts grew very well at pH 6.0. At ethanol concentration less than 10% (≤ 10% v/v), all the isolates except S. uvarum recorded slight growth while none grew at 19% ethanol concentration. CuSo4 tolerance result showed that moderate growths for each yeast at 1.0g/l, slight growth at 2.0g/l and no growth at 3.0g/l. All the yeasts grew at 0.01% - 0.02% concentration of Sodium metabisulfite while only S. cerevisiae and S. globosus had slight growth at 0.04%. S. carlsbergensis and S. uvarums how no growth at 0.04% and none of the isolates grew at 0.05%. Sucrose was the most suitable sugar from all the yeasts. S. cerevisiae had the highest CO2 production capacity of the four isolates. The result showed the ability of the yeasts to adapt to various physiological parameters. It is recommended that harnessing palm wine as yeast sources of any use both domestically and industrially should be encouraged.

Keywords: Growth, microorganism, palm wine, physiological study, yeasts