Pilot plant production of ethanol from cassava starch and fermentation kinetic studies

In this study, hydrolyzed cassava starch (containing glucose) was fermented in a fabricated 25.8 L pilot scale batch fermenter kept at a temperature of 30-34 ℃ and 4-6 pH for 108 h to study their fermentation kinetics. Acid treatment of the cassava starch hydrolysis was carried out using diluted sulphuric acid (1.5M) such that the maximum concentration of sugar obtained was found to be 42 g/mL after 180 min of hydrolysis, which is used as the initial sugar concentration for ethanol production using Baker’s yeast ( Saccharomyces cerevisiae ). Kinetic parameters ( µ 𝑚𝑎𝑥 = 0.0465 h -1 and 𝐾 𝑠 = 15.375 g/mL) were determined from and studied using the Monod kinetic model and the Logistic kinetic model, simultaneously. Findings reveals that the maximum biomass concentration, ethanol concentration, ethanol yield and the maximum % sugar utilization rate are 7.3 g/mL, 29 g/mL, 69% and 47.62 %, respectively after 96 h of fermentation. Specific growth rate based on the use of the Logistic kinetic model gave µ = 0.0225 h -1 . This study applied the dry weight spectrophotometric analysis and refractive index method respectively to analyze the biomass and sugar amounts, while the ethanol concentrations were derived from the specific gravity method. Diversification of yeast type (alternatively, Zymomonas mobilis , Candida albicans , Cryptococcus neoformans , Saccharomyces boulardii , Pichia pastoris , Kluyveromyces lactis etc.) in the production of ethanol and their separate examination to checkmate their resultant yield should be carried out in the future. Presently, the development of a universal kinetic model that is valid for an extensive range of fermentation methods, which is capable of providing a theoretical basis for the existing empirical models is essential in this field. By studying more fermentation processes and by integrating extra factors that affect fermentation, research will get closer to a more general model.