Enzymatic Hydrolysis Of Corn Straw And Lactic Acid Fermentation

Cellulose is the main ingredient of cell wall of plant fibre, which is the most abundant renewable resource on the earth, especially the crop straw in our country. Many scholar have been studying plant fibre to get them use high-efficiently. Based on the sufficient analysis of previous study, we used corn straw as raw material of hydrolysis for lactic acid production. In this work, two industrial available cellulases were selected to as catalysts. The effect of various factors to the enzymatic hydrolysisn the kinetics model of enzymatic hydrolysis of cellulose and lactic acid fermentation were studied respectively.The rate of enzymatic hydrolysis of cellulose was very slow and restricted by many factors. The optimum conditions for enzymatic hydrolysis of cellulose was studied and the concentration of reducing sugar was measured by DNS. There was no report about the two cellulases (Suhong cellish L and Cellusoft L), which were used in weave industry for polishing, hydrolyzing plan fibre. By selecting the two cellulases to hydrolyzing corn straw, it was discovered that the activity of cellulase was sensitive to the variety pH and the most suitable pH is different from different cellulase and related to temperature. The most suitable pH for Suhong cellish L is 4.4 and Cellusoft L is 4.8. The temperature for enzymatic hydrolysis was the integration of the rate of enzymatic hydrolysis and the heat denaturalization of cellulase. As temperature rising, the former was accelerated, and however the latter was accelerated too. The most suitable temperature also varied with other factors such as time. Under the experimental condition, if the hydrolystic time was prolonged from 16h to 24h. it changed from 55 ℃ to 50 ℃ for the two cellulases. It also found that certainconcentration of non-ionic surfactant (tween) and metal ionic in the hydrolysis system stabilized cellulase and accelerated enzymatic hydrolysis. Under the optimized condition for Suhong cellish L hydrolyzing of corn straw, the concentration of reducing sugar reach 42.5 mg/mL in 48 h.Hydrolysis of cellulose under enzyme and acid hydrolyzing was also studied, the hydrolysis properties of Suhong cellish L and Cellusoft L compared with dilute sulfuric acid from the main affecting factor of hydrolysis (time temperature substrate concentration etc) and mechanism. The yield of hydrolyzing corn straw increased by 33% if combining enzyme hydrolyzing and acid as pretreatment.According to the mechanism of enzymatic hydrolysis of cellulose, the kinetic equation of enzymatic hydrolysis had been deduced with rational hypotheses; Parameters of the kinetic equation were figured out by nonlinear regression with the summation of the square of relative deviation minimized, the calculated value was coincided with experimental result comparatively.Lactic acid fermentation by Rhizopus oryzae with the hydrolyzate as carbon source was also studied. Conditions of fermentation and culture medium for Rhizopus oryzae were optimized, under the optimized condition, the concentration of lactic acidreach 21.8 mg/mL and the ratio of transform was 56% in 75 h.In this work, there are much help to produce lactic acid by developing for thecomprehensive utilization of the renewable lignocelluloses material. It will be a good contribution for the development of the rural area economy and for the sustainable development of our country.