Kinetics and modeling of pre-treated calotropis gigantea to ethanol production by DMC method

The potential of microbial pretreatment of Calotropis gigantea by Fusarium oxy sporum to degrade lignin and facilitate fuel ethanol production was investigated under direct microbial conversion (DMC) method. Pretreatment of lignocellulosic biomass using sodium hydroxide is basically a delignification process, in which a significant amount of hemi cellulose is solubilized as well Maximum reduction in lignin of 54.66% is achieved for 2.0% sodium hydroxide concentration, 90 min residence time at 120°C. The effect of initial substrate concentration, pH and temperature are identified as the major factors affecting ethanol production by DMC and these can be well studied by statistically designed experiments using central composite design. The validation of the statistical model and regression equation are conducted by taking initial substrate concentration of 33 g/l, pH of 5.52, temperature of 30.13°C. Maximum ethanol production of 9.3 g/l corresponding to 32% of theoretical yield is obtained under optimum conditions. The Logistic model for cell growth, Leudeking-Piret model for substrate utilization kinetics and product formation kinetics are tested. All the experimental results are found to be in good agreement with the theoretical predictions and all the models presented in this work provide a good description of biomass, product and substrate concentrations.