Evaluation and Optimization of Bioethanol Production from Pomegranate Peel by Zymomonas mobilis

The large amount of production and use of pomegranate in Iran has made the waste of this important product a suitable source for the production of bioethanol. This research examined the ability of Zymomonas mobilis for producing bioethanol from Pomegranate peel. The hydrothermal treatment method and enzymatic hydrolysis were used to release the fermentable sugars from PP particles. Cellulase loading of 30 U/g solid was used for enzymatic hydrolysis. Zymomonas mobilis PTCC 1718 was used as the ethanol-producing strain. The Response Surface Methodology experimental design was performed to optimize the fermentation process conditions for maximum ethanol production and minimum fermentation time. The amount of sugar released after hydrolysis was about 18.37% of the fresh PP weight. The amount of meat peptone and yeast extract (as nitrogen sources added to the medium), bacterial dry weight (as inoculum) and fermentation time were considered as the effective factors in the RSM experimental design. The maximum amount of 0.218 g ethanol was produced at 0.37 g meat peptone, 0.28 g yeast extract, 0.021 g bacterial dry weight and 30 h fermentation time (in 50 ml of culture medium). The maximum ethanol production yield of 45.5% (which is 89.2% of the theoretical yield) was achieved in this process. Z. mobilis has good ability for producing bioethanol from PP. However, more research should be conducted in order to industrialize the process.