Study On Biotransformation Of Agricultural By-products And Enzyme Production

The cellulose-decomposing strains exist in natural environment, and they have been widely investigated and considerable achievements have been obtained. Most of the researches focus on monocultures or a few of mixed strains, while, due to its complex structure, the cellulosic materials such as straws could not be biodegraded without an integrate lignocellulase system, commonly which can only be supplied by natural micro flora but not by monocultures or a few of mixed strains.Apart from separate cultures, we can also learn from the natural microflora world. Thousands of years have passed, natural microflora living with cellulosic materials have formed a balanced symbiosis. Microflora members cover deficiencies for each other, and the enzymes produced constructing an integrate lignocellulase system, can play the role of cellulosic material bioconversion. Although the biodegradation of cellulosic materials by natural microflora may be slow, their abundant metagenome resources give the potential to realize the aim of high effective and low-cost cellulosic materials bioconversion without high-energy-cost pretreatment. In this paper, by augmenting enzyme-producing strains, a symbiotic consortium was constructed for cost-effectively producing enzymes by solid state fermentation using rice straw et.al as the main substrate, and apple peel and wheat bran as aiding compositions to favoring the enzyme-producing process. At last we used enzyme activities, SEM and Metagenomics to observe the effect of bioconversion. The results as follows:1. The rice straw microflora suggested abundant flora, which of them have the ability of cellulose bioconversion, somewill maintain the balance of micro-ecological system according to the results of Metagenomics.Through response surface methodology, a multi-enzyme was produced in which the optimal CMCase activity hits to12.27U/gds when rice straw, wheat bran and apple peels of1:1.33:0.66(w/w/w), and moisture ratio of1:0.5(solid:liquid), yet the activities of other three enzymes, xylanase, amylase and pectinase, also satisfactory. Changing the three independent variables, i.e., moisture content, wheat bran and apple peel, the multi-enzyme composition could be regulated. Further more, for amylase, the most effective variables was wheat bran, moisture level and apple peels have low significance. For CMCase, the most effective variables was wheat bran and apple peels, moisture level will inhibit the production of CMCase. For xylanase, the most effective variables was wheat bran and moisture level, apple peels will inhibit the production of xylanase.2. Through response surface methodology, FPAase was produced in which the optimal production hits to3.88U/gds when corncob, wheat bran and apple peels of1:1.45:0.42(w/w/w), and moisture ratio of1:2.66(solid:liquid). The SEM results revealed that the structure of corncob have varied obviously with pre-and post treatment, the clear fiber structure become obscurer, compact sarciniforms disappear, with corncob mircroflora the corncob complete bioconversation.3. Through response surface methodology, amylase was produced in which the optimal production hits to127.53U/gds when bagasse, wheat bran and apple peels of1:1.5:0.19(w/w/w), and moisture ratio of1:3.05(solid:liquid).In the interactive effects on the wheat bran and moisture, we found that wheat bran was the main effect, when additive amount of wheat bran was determined, the amylase was determined also.4. Through response surface methodology, xylanase was produced in which the optimal production hits to6.80U/gds when maize straw, wheat bran and apple peels of1:2.19:0.06(w/w/w), and moisture ratio of l:6.22(solid:liquid). When additive amount of wheat bran was above3g, apple peels can play the role of wheat bran, if we increase the amount of moisture level, the amylase will increased rapidly.