A Potential Substitute of Fermentation Material in Gansu Province

Abstract

Sweet sorghum has the advantage to grow on saline-alkaline barren land, and is very suitable to plant in Gansu province for different uses such as feedingstuff and fermentation material. However, in the previous test, it was found that the biomass of Saccharomyces cerevisiae using sweet sorghum juice produced in Gansu province was as low as 8.5 g/l and could not meet the needs of mass production of yeast and ethanol. To attain high biomass, the optimal culture conditions were investigated. It was found that the proper culture time, temperature, pH and sugar content for yeast growth in sweet sorghum juice were 20 h, 30 °C, 6.0 and 80.5 g/l, respectively. An orthogonal design L9 (34) was used to test the optimal inorganic salt supplement quantity. The results showed that high biomass yield was achieved when the juice was supplemented with 2.0 g/l (NH4)2SO4 which was a little bit different from other report. Finally, the biomass yield of 19.3 g/l and conversion efficiency (yeast to sugars) of 0.452 was obtained in a 10-100 liter bioreactor under the determined optimal conditions. These findings demonstrate that with some modifications on the culture conditions, sweet sorghum juice is a very potential substitute of fermentation material for yeast and ethanol production in Gansu province.