초록
De-oiled Pongamia pinnata seed cake has been gaining attention as a promising feed stock for ethanol production owing to the large amounts of carbohydrates (42%w/w) present in the seed biomass. This, coupled with the potential of seed productivity (>200,000tannum<SUP>-1</SUP>) makes it suitable for the sustainable production of ethanol. The present research explores the application of glucose obtained from acid hydrolysis of the seed cake for ethanol production in a three step process: acid treatment, neutralization and fermentation. The Taguchi robust design of experiments was employed to study the effects of the parameters including acid type (H<SUB>2</SUB>SO<SUB>4</SUB>, HCl, H<SUB>3</SUB>PO<SUB>4</SUB>), acid concentration (2-6%w/w), and temperature (80-100<SUP>o</SUP>C) on the formation of glucose. Among the reaction variables considered, acid concentration and temperature showed a positive effect on glucose release from the biomass with HCl the best catalyst compared to H<SUB>2</SUB>SO<SUB>4</SUB> and H<SUB>3</SUB>PO<SUB>4</SUB> showing highest glucose formation (173.4gkg<SUP>-1</SUP> seed residue) at 100<SUP>o</SUP>C with 6%w/w HCl concentration. The energy required for this pretreatment was estimated to get an insight into the process energy demand (1080-1110KJkg<SUP>-1</SUP> of seed cake). Downstream processing before fermentation included neutralization. Fermentation of hydrolysis product obtained from 2%, 4% and 6% HCl treatments (carried out using Saccharomyces cerevisiae) gave 67.52, 74.98 and 88.62gethanolkg<SUP>-1</SUP> dry seed residue, respectively, corresponding to ~31.45%, 34.92% and 41.28% of theoretical ethanol (214gkg<SUP>-1</SUP>) formation, calculated based on ethanol produced per gram of carbohydrate in the seed residue.