Activity of Zymomonas species in palm-sap obtained from three areas in Edo State, Nigeria.

Abstract

The bacterium Zymomonas mobilis was isolated from fresh palm-sap samples from three different locations as to determine the contribution of the bacterial isolate to alcohol production in palm-wine. Carbohydrate (sugar) fermentation, alcohol tolerance, and growth of the bacterium at different pH and temperature values were determined; and a comparison of sugar fermentation by Z. mobilis and Saccharomyces cerevisiae was also determined. Z. mobilis contributes much to the fermentation of palm-wine due to its ability to ferment sucrose, glucose and fructose which are the main sugars in palm-sap. The bacterium reached its maximum density of 2.72 x 10 7 cells/ml between 12 and 15 hrs after tapping of the palm-sap. Z. mobilis is acid and alcohol tolerant being able to grow at pH values between 4.0 and 7.0 and in alcohol concentration of between 2.5% and 15% respectively. Z. mobilis was also found to ferment sugars at a faster rate than Saccharomyces cerevisiae. Statistical analysis of the data obtained using ANOVA showed that there is no significant difference at p = 0.05 level of significance in the growth of isolates of Z. mobilis obtained from the three locations under different pH, alcohol and temperature values. @JASEM Palm-wine is an alcoholic beverage obtained from the fermentation of the sugary sap of various palm species in Nigeria. It is usually obtained from Raphia vinifera, Raphia hookeri, and Elaeis guineensis by methods described by Bassir (1965), Faparusi (1966) and Okafor (1972). Raphia palms usually yield more sap than oil palms although raphia palms can only be tapped once in its life time because its terminal inflorescence is destroyed during tapping (Okafor, 1977).