Statistical optimisation of saccharification process using Amorphophallus paeoniifolius tubers into fermentable sugars for bioethanol production in stirred tank batch reactor (STBR)

Current technologies to produce biofuels from various renewable feedstocks have considerably captured vast scientific attention since they can be used as an alternative fuel. Bioethanol being one of the most interesting biofuels and due to its positive impact on the environment has been categorised significantly in terms of scientific and technological investments. The aim of this study was to investigate tubers of Amorphophallus paeoniifolius biomass as a feedstock for bioethanol production. The composition analysis of A. paeoniifolius tubers revealed high carbohydrate content (78.30 ± 0.33%). The feedstock was subjected to physicochemical pre-treatment by treating with dilute acid followed by pressure cooking. The pre-treatment factors were optimised by CCD using RSM approach. The optimum condition was found to be 1.32% (v/v) of HCl, 5.83% (w/v) of elephant foot yam biomass and 66.84 min of pressure-cooking time yielding 45.87 g/L of total sugar. The second-order polynomial equation was generated for the saccharification of biomass and validated with R2 0.89. The fermentation of pre-treated biomass in the presence of Saccharomyces cerevisiae MTCC170 yielded 22.12 ± 0.62 g/L of bioethanol at 120 h utilising 92% of initial total sugar. The resultant ethanol yield and productivity was estimated to be 0.51 g/g and 0.30 g/(L/h), respectively. The Gompertz model equation was applied to experimental data using nonlinear regression with least square method and the kinetic fermentation parameters such as maximum ethanol concentration (Pm), production rate (rpm), and lag phase (h) were estimated to be Pm = 21.90 g/L, rpm = 0.57 g/(L/h) and tL = 8.22 h.