EFFECT OF pH AND SUBSTRATE CONCENTRATION ON BIO-ETHANOL PRODUCTION FROM POTATO PEEL WASTE USING Saccharomyces cerevisiae

Abstract

Fermentation is a metabolic process of microorganisms to obtain energy by breaking down organic compound. Potato peel waste was fermented with different concentration substrate (1gm, 2.5gm, 5gm, 10gm, 15gm, 20gm and 25gm) with 1% yeast and pH4.5 in different fermentation period (4th day, 8th day, 12th and 16 th days) with the aim of optimizing the substrate concentration for ethanol production. Among the different substrate concentration 10 gram of substrate produced more quantity of ethanol on 4th day of fermentation. Accordingly, 10 gram substrate considered as optimum for ethanol production and subjected to acid pre-treatment. After the acid pre-treatment, ethanol production was boosted as compared with untreated 10 gram substrate. The maximum ethanol production for 10g untreated substrate was only 5.06%, whereas that of acid-pretreated was 7.46%. The reducing sugars contents decreased gradually as the fermentation period increased. Moreover, on 4th day of fermentation period, the highest reducing sugar concentration (29.33mg/ml) was obtained from acid pretreated potato peel waste of 10gram substrate, whereas the same substrate concentration showed 26.08mg/ml in untreated substrate. The cell biomass was higher in acid pre-treated substrate (31.2mg/ml) than untreated ones (26.6mg/ml). Moreover, the acid pretreated substrates showed the less lignin content than the untreated substrate, whereas highest removal of lignin percentage (7.4%) was observed in 10gram acid pretreated substrate compared with untreated substrate. The production of ethanol was increased with increasing the level of pH up to 4.5 after this suddenly declined rate of ethanol production. The maximum ethanol production (7.46%) was observed at pH 4.5 in acid pre-treated. The cumulative bio ethanol production was observed in different fermentation periods for optimum substrate concentration in acid pre-treated and untreated substrate. The maximum ethanol production was observed on 4th day of fermentation in acid pre-treated substrate. If the fermentation period increases, the rate ethanol production also decreased in treated and untreated substrate (10gram). The study revealed that it is possible to produce bioethanol from potato peel waste. Therefore, it is recommended to conduct pilot studies to maximize ethanol yield.