ETHANOL PRODUCTION FROM ORANGE AND PAPAYA FRUIT PEEL WASTES

Abstract

Ethanol produced by microbial fermentation of biomass is used primarily as a substitutive for gasoline. It is produced by using an eco-friendly method to replace fossil fuel. Therefore, this study was focused on co-fermentation of orange and papaya fruit peels waste for bioethanol production with the objective of evaluating its potential for ethanol production with different concentrations (100 g orange peel, 75 g orange peel +25 g papaya peel, 50 g orange peel +50 g papaya peel, 25 g orange peel +75 g papaya peel and 100 g papaya peel). Orange and papaya fruits peel waste were subjected to batch fermentation for 16 days with Saccharomyces cerevisiae. Batch fermentation of orange and papaya mixture of different concentration types for ethanol by Saccharomyces cerevisiae was investigated with different initial concentrations of the substrates and fermentation was carried out at two inoculums concentrations (1% and 0.5%). Ethanol content was also measured every 4th days of the fermentation period. The temperature and the pH for the fermentation were adjusted at 30°C and 4.5 pH, respectively. At 4th, 8th, 12th and 16th day of fermentation period the reducing sugars of each substrate and cell density were also measured. The results showed that reducing sugar decreased from 4th up to 16th day and the cell density increased up to 12th day. However, after12th day of fermentation the cell density started to decrease. Maximum ethanol production was observed from 50 g orange peel and 50 g papaya peel with 1% inoculums (26.03 ml) at 12th day of fermentation period. With increased time of fermentation the ethanol yield and cell density also increased up to the 12th day of the fermentation. In this study, the effect of substrate concentration and inoculums concentration on ethanol production was also investigated. The result showed that the greater substrate concentration with 1% inoculum yielded more ethanol than substrate with 0.5% inoculums. Therefore, substrate concentration and inoculums concentration are directly proportional until it reached the optimum level for ethanol production.