Optimization and kinetic parameter estimation of bioethanol production from freely available Sri Lankan fruits in batch fermentation

Bioethanol is used in many countries as an alternative to gasoline, mainly due to better emission characteristics. Since Sri Lanka imports fuel for its whole transportation requirement, this research aims optimization and kinetic parameter estimation of bioethanol production from freely available Sri Lankan fruit wastes in batch fermentation. Bioethanol production was carried out using three different freely available overripe fruits in Sri Lankan: banana (Musa spp., embul kesel variety), papaya (Carica papaya) and jackfruit (Artocarpus heterophyllus). Kinetic evaluation of the fermentation process and optimization bioethanol yields were carried out by changing the type of fruits, type of microorganism (Saccharomyces cerevisiae and Pseudomonas mendocino (PM)), concentration of the substrate (1:1, 1:1.5, 1:2 w/w ratio of fruit and water), pH (4.3, 5.0, 5.7), and temperature (27, 32, 350C). Estimation of the kinetic parameters was carried out using Monod and Modified Gompertz equations by fitting experimental data. Optimum parameters found for the fermentation of banana using PM microorganism were 1:1 (w/w) concentration at pH 5 and 350C with a maximum bioethanol yield of 13 vol%. Experimental data were well fitted with Monod model and Gompertz model, with a higher regression coefficient of R2 99.81 and R2 > 99.37 respectively. Comparative to the reported, 12.8 vol% bioethanol yield from banana by fermentation using PM microorganism at room temperature a higher bioethanol yield of 13 vol% could be obtained by fermentating banana fruit mass using PM microorganism with 1:1 (w/w) concentration at pH 5 and 350C temperature.