Direct Conversion of Fruit Waste to Ethanol Using Marine Bacterial Strain Citrobacter Sp. E4

Ethanol tolerant strains were isolated from the marine waters of Digha and Shankarpur of West Bengal, India and screened for ethanol production using several domestic wastes including, paper, kitchen, garden, and fruit wastes. Strain E4 was found to be the most efficient in ethanol production through fermentation of kitchen and fruit waste. Phylogenetic analysis of the 16S rRNA gene of strain E4 showed its closeness to Citrobacter sp. Production of 2.96 g/l of ethanol was obtained using fruit waste using High-Performance Liquid Chromatography (HPLC) analysis. The yield of ethanol production was obtained as 0.13 g of ethanol/g of reducing sugar present in fruit waste. Although after optimization of fermentation condition, the yield was improved to 0.30 in batch scale. The production was optimized using Central Composite Design. The production was scaled up to 41 culture volume in the stirred tank bioreactor. Finally, a distillation of fermentation broth resulted in 16.10 ml of product with a yield of 0.30 g of ethanol from 1 g of fruit waste. Thus the isolated marine strain Citrobacter sp. E4 could be potentially used for ethanol production from fruit wastes without any pretreatment in a cost-effective and eco-friendly way. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.