Yeast and lactic acid population relationship in palm wine and their effects on the production of ethanol in Enugu Ezike south eastern Nigeria

Abstract

Palm wine produced traditionally and consumed by many people in the South eastern part of Nigeria is a whitish liquid formed by naturally fermenting the sugary sap from various palm plants. In this study, we evaluated the population of yeast and lactic acid bacteria in palm wine with regards to its ethanol concentration from three communities in Enugu Ezike, Enugu State. We monitored the isolation of microbial population as well as biochemical characteristics of fermenting palm wine samples using culture-dependent and culture-independent methods. The fermentation step was performed within time interval and completed after 48hrs. Its acidity increasedprogressively with the production of lactic and acetic acids by bacteria.During the fermentation, palm wine microbial  numbers (log10 CFU/ml) varied between 1.6 x104 to 7.6 x107 for yeast and 4.5 x 104 to 7.8 x 107 for lactic acid bacteria respectively. Similarly, pH and alcohol level of palm wine samples during the fermentation varied between 3.0 to 5.8 and 0.2 to 5.3 respectively. Statistical analysis revealed that there was no significant difference in both yeast and lactic acid bacteria population at 24hrs. At this time, there was an increased metabolic activity, leading to an increase in ethanol production. At 36-48hrs, there was a slight decrease in both the lactic acid bacteria and the yeast, indicating a reduction in source of carbon.The analysis of the yeast and the lactic acid bacterial population revealed different yeast and bacterial population. Bacteria compete with yeast for nutrients during ethanol  production process, potentially causing economic losses. Therefore, it is important to have a better understanding of the abundance and the change in population of lactic acid bacteria and yeast throughout the bio-ethanol process in order to achieve design a more efficient relationship in lactic acid, yeast and ethanol production processes.

Keywords: Bacteria, ethanol, lactic acid, palm wine, yeast