Statistical optimization of alkaline treatment of pomegranate peel waste for bioethanol production

The dwindling of conventional energy resources has necessitated the need to explore new and sustainable forms of energy. In this regard, economical production of bioethanol from various degradable wastes has gained the attention of researchers in the last few years. The current study investigated the alkaline-hydrolysis optimization of pomegranate peel waste (PPW) for bioethanologenesis. The alkaline hydrolysis optimization was carried out by response surface methodology. Significant values (g L-1 ) of reducing sugars (142.4 +/- 0.05), total carbohydrates (359.4 +/- 0.02), weight loss (74.8 +/- 0.031), extractives (1.83 +/- 0.05), hemicellulose (16.7 +/- 0.214), crude cellulose+ insoluble lignin (75.7 +/- 0.178), and soluble lignin (5.8 +/- 0.063) were obtained when PPW was hydrolyzed with 0.5% KOH at 80 degrees C for 90 min with 36.10% conversion efficiency. Three novel ethanologenic yeasts, viz., Saccharomyces cerevisiae K7, Metschnikowia sp. Y31, and Metschnikowia cibodasensis Y34 were used to ferment the PPW hydrolyzate after detoxification with 2.5% charcoal. The significant ethanol yields (g g(-1)) after fermentation with Metschnikowia sp. Y31 and M. cibodasensis Y34 were appeared as 0.32 +/- 0.005 and 0.29 +/- 0.003, respectively, on the third day of incubation, while S. cerevisiae K7 produced 0.30 +/- 0.003 g g(-1) of ethanol on the first day of incubation. Our findings of the present study will be helpful for the economical bioconversion of frequently available organic wastes into ethanol at industrial scale.