Optimization Of Media Composition For Hydrogen Gas Production From Hydrolyzed Wheat Starch By Dark Fermentation

摘要

Effects of N/C, P/C and Fe(Ⅱ)/C ratios in fermentation medium on biohydrogen production by dark fermentation of acid-hydrolyzed wheat starch was investigated. The powdered wheat was autoclaved at pH = 3 and 90 ℃ for 15 min and the resulting sugar solution was fermented after external addition of N, P and Fe(Ⅱ) to overcome nutrient limitations. Box-Wilson statistical experiment design was used by considering the N/C (0-0.05, w w~(-1)), P/C (0-0.02) and Fe(Ⅱ)/C (0-0.03) ratios as the independent variables while the hydrogen yield and specific hydrogen production rate (SHPR) were the objective functions to be optimized. A quadratic response function was used to correlate the response functions with the independent variables. Low levels of the variables (N/C < 0.02, P/C < 0.01, Fe(Ⅱ)/C < 0.01) resulted in low hydrogen yield and SHPR due to nutrient limitations and high levels of nutrients caused inhibitions. The optimum conditions yielding the maximum hydrogen yield (Y = 2.84 mol H_2 mol~(-1) glucose) were N/C = 0.02, P/C = 0.008 and Fe(Ⅱ)/C = 0.015. The maximum SHPR (96 mL H_2 g~(-1) biomass h~(-1)) was obtained at N/C = 0.025, P/C = 0.008 and Fe(Ⅱ)/C = 0.015 (ww~(-1)).