INVESTIGATION OF MAERUA SHRUB (Maerua subcordata) AND YEASTS FROM FINGER MILLET (Eleusine coracana) FOR PRODUCTION OF CHEAP AND EFFICIENT BIOETHANOL IN KENYA

Abstract

Bioethanol is an attractive energy source in comparison to fossil fuels because it is renewable and environmentally friendly. The first generation bioethanol is unsustainable due to high cost of food crops and causes food insecurity. In addition, there is need to search for a yeast with high ethanol producing. Yeast with high adaptation to adverse conditions increase ethanol productivity causing economic viability. This study investigated the use of maerua shrub and fermentation using finger millet malt yeasts (Y1 and Y2) as a cheap and efficient way of producing bioethanol. Morphological and microscopic characteristics of purified cultures were determined. The physiological characterization of the yeast were done by looking at the effect of temperature, ethanol concentration and glucose content on the growth of the yeasts using optical densities determined by UV-visible spectrophotometer at 600 nm. The concentration of sugar was determined by titrimetric technique using standardized Fehling’s solution. Samples were fermented for 48 hrs at 35 o C, distilled, oxidised and analysed using UV-Visible spectrometer at 595nm. Statgraphics centurion was used in data analyses. The isolated yeasts Y1 showed white colony, Y2 creamy colour and both indicate multilateral budding, characteristic of Saccharomyces strain. The mean optical densities on growth of yeast at various temperature were Y1 (0.4201), Y2 (0.5097) and Saccharomyces cerevisiae, Y3 (0.9287), p = .467, ethanol concentration on yeasts were Y1 (0.8434), Y2 (0.4185) and Y3 (0.9672), p = .117, had no significant difference, while glucose concentration for Y1 (0.8329) which was significantly lower compared to both Y3 (1.1726) and Y2 (1.3907), p = .0045. The reducing sugar content in (mole/L); maerua shrub (0.3906), sorghum (0.4426) both were comparable, but significantly lower than cassava (0.7760), maize (0.7054) and sugarcane molasses (0.8980), p = .0001. The ethanol concentration and productivity (g/L/h) from various plants were; cassava (64.052±0.098, 1.334 g/L/h), maize (66.670±0.227, 1.389 g/L/h), sorghum (62.382±2.148b, 1.300 g/L/h) and maerua shrub (61.988±0.160, 1.291g/L/h) which were remarkably higher compared to sugarcane molasses (49.978 g/L, 1.041g/L/h) when fermented by Y2. Y2 gave higher ethanol production than Y1 which produced lower productivity in relation to (Y3). The yeast Y2 isolated from finger millet malt can be used in fermentation and Maerua Shrub to be used as sugar source for bioethanol.