Utilization of Gamma Irradiation For Bio Fuel Production by Microorganisms

With the growing crisis in fossil fuel and environmental pollution problems worldwide, bi oethanol has become one of the most promising bio fuels and many studies have been focused on improving the efficacy of the bi oethanol production process. Due to the high cost of bi oethanol production process, this work was concerned with producing bi oethanol from low-cost raw agro-industrial feedstock and utilizing gamma irradiation technology to increase conversion efficiency of these materials to bi oethanol. 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 bi oethanol 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 bi oethanol production was also investigated. Gamma irradiation had negative impact on cell counts, but not the viability, of both organisms. The highest bi oethanol 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 bi oethanol 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. On sugarcane bagasse, hydrolyzed with 2 % (v/v) H₂SO₄ at 120°C for 60 min, the co-culture of Z. mobilis irradiated at 0.1 kGy and Sacch. cerevisiae irradiated at 0.3 kGy produced 11.3 g L^-1. When the last pretreatment was preceded with irradiation of sugarcane bagasse at 75 kGy, 15.6 g L-1 of bi oethanol was achieved. On potato peels, hydrolyzed with 6 % (v/v) H₂SO₄ at 100°C for 30 min, the same co-culture of irradiated Z. mobilis at 0.1 kGy and Sacch. cerevisiae at 0.3 kGy produced 9.2 g L^-1 of bi oethanol. When the last pretreatment was preceded with irradiation of the potato peels at 75 kGy, 12.1 g L^-1 of bi oethanol was achieved