Study Of Synthesis Chitosan From Fungi Cultivated With Corn-cob Enzymatical Hydrolysic Products

Corn-cob is a kind of cellulose and xylan-riched agriculture byproduct.The synthesis of cellulase and xylanase with pretreated corn-cob as carbon source by Trichoderma viride and the hydrolysis with this enzyme pretreated corn-cob are studied in this thesis. Then using hydrolysates as carbon source to cultivate fungi (Aspergillus niger, Trichoderma viride, Rhizopus delemar, Rhizopus oryzae) and extracting chitosan from mycelia are studied.The result of cellulase and xylanase synthesis shows that the kind and concentration of carbon source, the kind of nitrogen source, and the C/N, the initial pH value, the culture temperature,etc all have some effects.The better preducing enzyme term is using 20g/L 1% NaOH pretreated corn-cob as carbon source and the peptone+ammonium sulfate+urea as nitrogen source, regulating C/N 5.6, initial pH value 4.8, ulture temperature28眑癈, 150r/min.The cellulase and xylanase activity reached 40.7IU/mL (CMC-ase activity) and 141.32U/mL respectively after 120 hours cultibvation.Enzyme hydrolysis result shows that the better substrate is 10% NH3 H2O pretreated corn-cob. And when substrate concentration is 15%(W /V), the optical hydrolysis condition is pH 4. 8, 50 C, enzyme quantity 30U/g substrate.After 24 hours the reducing sugars concentration reached 62.3g/L and almost kept constantly.The result shows that the yield of chitosan from Aspergillus niger is larger than Trichoderma viride, Rhizopus delemar and Rhizopus oryzae. The optimum conditions of cultiviating Aspergillus niger to produce chitosan using enzymatic hydrolysate as substrate is as follows: reducing sugars concentration 20g/L, culture temperature 30癈, initial pH value 7. 0, 150r/min. In this condition , mycelia and chitosan concentration reached 8. llg/L and 0.69g/L respectively. The content of chitosan in mycelia is 8.51% . Chitosan yield is 34. 5mg/(g reducing sugars) .