Production of ethanol by Enterobacter sp. EtK3 during fruit waste biotransformation

摘要

Ethanol resistant bacterial strain Enterobacter sp. EtK3 was isolated from kitchen wastewater through enrichment culture. The isolated strain was found to produce ethanol by fermenting dried banana peel without any pre-treatment. Ethanol production was confirmed by High-Performance Liquid Chromatography (HPLC) analysis of the fermentation broth. Sequence analysis of the 16S rRNA gene of bacterial isolate EtK3 confirmed its relation with the Enterobacteriaceae family. The temperature of 35 degrees C with pH 7 utilizing 15.5 gL(-1) fruit waste was found to be most favorable for ethanol production after a two-level, three-factor optimization study using Response Surface Methodology (RSM). In the optimized condition, a 23.6% yield of ethanol was obtained. Kinetic study of cell growth, ethanol production and reducing sugar utilization revealed that ethanol production was growth associated with product inhibition at the late log phase. Proximate analysis of pre and post-fermented fruit waste showed subsequent depletion of the fixed carbon content of waste indicating carbon utilization of EtK3 strain from the waste sample. Waste degradation was further confirmed by Scanning Electron Microscope with Energy Dispersive X-Ray (SEM-EDX) and Fourier Transform Infrared Spectrometer (FTIR). An empirical representation of the waste was derived to produce a complete mass balance of the whole ethanol production process from fruit waste.