Abstract

This study was to examine the efficiency of native microorganisms, in relation to the commercial bacterium Clostridium thermocellum ATCC 27405 for bioethanol production from waste watermelon on a pilot scale. The raw material was subjected to a grinding process for the later stage of hydrolysis under different temperatures using Aspergillus fumigatus and Leuconostoc dextranicum native microorganisms. This was followed by fermentation using control strains of Zymomonas mobilis (native microorganism) and C. thermocellum ATCC 27405. After hydrolysis, the fermentation product was evaluated by physico chemical analysis, pH determination and reducing sugars concentration using refractometry. Finally, the product obtained was subjected to vacuum distillation to increase the grade of purity. It was there after analyzed using pycnometry and gas chromatography (GC). GC results revealed that the yield of ethanol from hydrolysis and fermentation by native strains was improved by 27.62%, compared to yields of ethanol obtained from Z. mobilis (11.62%) and C. thermocellum (3.10%). It was therefore concluded that the native strains were more efficient in hydrolysing and fermenting watermelon compared to the commercial C. thermocellum and Z. mobilis.

Key words: Aspergillus niger, Clostridium thermocellum ATCC 27405, Zymomonas mobilis, hydrolysis, fermentation processes.