Characteristics of hydrogen production from bean curd manufacturing waste by anaerobic microflora

The hydrogen production from bean curd manufacturing waste by anaerobic microflora was investigated using batch experiments at 35 °C. The anaerobic microflora was obtained from fermented soybean-meals and maintained using a sucrose-limited medium in continuous culture. A solution of an organic substrate without solid component such as rough fiber in bean curd manufacturing waste was used for the experiments. After the inoculation, hydrogen production immediately occurred and almost ceased at 12 h. The final concentration of hydrogen in gas produced was 63% H₂. During hydrogen production, carbohydrate was rapidly degraded while protein degradation was hardly observed, suggesting that carbohydrate was the main source of the hydrogen production. The hydrogen yield was 2.54 mol of H₂ mol^-1 of hexose utilized if hydrogen gas was produced from only carbohydrate degradation. At a carbohydrate concentration greater than 3,720 mg l^-1, the rate of hydrogen production rate significantly decreased. The rate of alcohol production was remarkably increased with increasing carbohydrate while the rate of volatile fatty acid production was hardly changed. The results indicated that the metabolic pathway and the amount of hydrogen production would be significantly influenced by the carbohydrate concentration.