UTILIZATION OF GAMMA IRRADIATION FOR BIOFUEL PRODUCTION BY MICROORGANISMS

Abstract

With the growing crisis in fossil fuel and environmental pollution problems worldwide, bioethanol has become one of the most promising biofuels and many studies have been focused on improving the efficacy of the bioethanol production process. Due to the high cost of bioethanol production process, this work was concerned with producing bioethanol from low-cost raw agro-industrial feedstock and utilizing gamma irradiation technology to increase conversion efficiency of these materials to bioethanol. Sugarcane bagasse and potato peels were hydrolyzed by dilute sulphuric acid (2 and 6 % v/v) and the resulted hydrolyzates were fermented by either Zymomonas mobilis ATCC 29191, Saccharomyces cerevisiae ATCC 7754, or co-culture of both organisms. The effect of gamma irradiation on bioethanol production was studied by exposing the producing microorganisms or feedstock to different doses of γ-rays. Effect of combined treatment of feedstock, using gamma irradiation and dilute acid, on bioethanol production was also investigated. Gamma irradiation had negative impact on cell counts, but not the viability, of both organisms. The highest bioethanol production, from acid-hydrolyzed sugarcane bagasse, was from treatment with 2 % (v/v) H2SO4 at 120°C for 60 min, fermented with Sacch. cerevisiae (irradiated at 0.3 kGy), giving 10.3 g L-1. The highest bioethanol production, from acid-hydrolyzed potato peels, was from treatment with 6 % (v/v) H2SO4 at 100°C for 30 min, fermented with Sacch. cerevisiae (irradiated at 0.3 kGy), giving 7.5 g L-1.