| To detect the metabolic characteristic of rice straw degradation by composite microbial system WSC-6, we cultured WSC-6 in the media used rice straw as the limiting carbon source. The rice straw was added in the style of different quantity once or the same quantity at the different time intervals during 90 days culture. The systems were cultivated under static condition at 50℃. The degradation ratio，absolute degradation quantity，products from degradation and dynamics of pH value of fermentation system were all investigated. The results showed: when 1% rice straw was added once, the pH of fermentation system decreased from initial 7.8 to 6.0 within the first three days inoculation, and after six-day cultivation, it increased to 8.0 and was stable. For dissolved oxygen concentration (DO), the value was maintained at range of 0.01 to 0.12 mg·L-1 of microaerobic condition. During the rice straw degradation, more than ten kinds of products including ethanol, acetic acid, lactic acid and glycerol and so on were detected using GC-MS. Especially, the highest concentration of lactic acid among all products was 7.381 g·L-1 at 24 h after inoculation. During 90-day cultivation, for the addition treatments of the different quantity once, the more rice straw added, the quicker and lower the pH decreased, and the longer time intervals returned the pHs were. Especially for 5.0% addition, when 5.0% of rice straw was added once, pH did not increase again after it decreased. Among the addition of the same quantity at the different time intervals, the trend of decrease-increase in pH at 12-day and 15-day intervals could be repeated and high degradation activity well maintained. After 90-day of inoculation, the highest degradation ratio occurred in the treatment at 15-day interval, which was 86.7%. The highest absolute quantity occurred in the treatment at 6-day interval, which was 32.4 g. The trend of pH changes can indicate the activity of lignocellulose degradation and degradation process of the WSC-6. |
