Growth kinetics and modelling of S. cerevisiae (NCYC 431) during de-lignified waste banana fermentation and chemical characterization

Abstract

S. cerevisiae (NCYC 431) growth kinetics was studied using mathematical models in order to ascertain the optimum operational parameters for banana waste fermentation. Chapman-Richards model was used to describe yeast growth kinetics under varying pH and temperatures and the results were compared to Bergter and Andrew models. Alkaline-delignification of the wastes was done to solubilize lignin prior fermentation. This is because lignin is a complex organic plant compound that has been reported not to be degraded easily by many microorganisms. From the results temperatures 22–28 °C and pH 4.5–5.6 were noted as optimum for yeast growth on delignified waste bananas (DWB). Chapman model results were close to Bergter and Andrew models with very low RMSE. Delignification was noted to aid yeast growth with higher microbial populations (log10 cfu/g) registered with DWB samples as compared to non-delignified waste bananas (NDWB). Also, chemical characterization of the DWB and NDWB indicated higher proteins and lipids in the former than the latter by 3 and 4% respectively. This suggested the possible use of the upgraded wastes as chicken feed supplements. Higher minerals in DWB of 8.6% also suggested the possible use of the waste as a nutrient-rich fertilizer.