Study On Production Of Fungal Chitosan Using Xylose Mother Liquid As Substrate

Chitosan,copolymer of glucosamine and N-acetyl glucosamine is derived from the deacetylation of chitin.With the excellent properties of non-toxicity,biocompatibility,biodegradation,chitosan has has a broad range of applications in fields of food,agriculture,enviromental,tissue engineering and biomedical.On a commercial scale,chitosan is mainly obtained from crustacean shells,even though chitosan is major component in cell wall of zygomycetes.In this thesis,we have focused on the extraction methods and purification of chitosan by fungal fermentation using xylose mother liquid as inexpensive carbon sources.Four different filamentous fungi were used for the production of chitosan by fermentation in xylose medium.Actinomucor elegans was found to be the best strain for preparation of chitosan.The medium components considered for initial screening in a Plackett-Burman design,the corn steep powder,KH2PO4 and gibberellic acid were identified as significantly influencing chitosan production.Response surface methodology was applied to determine the optimal levels for chitosan production,and the optimum medium composition was xylose mother liquid 4%,corn steep powder 5%,KH2PO4 0.35%,MgSO4·7H2O 0.1%,CaCl2 0.1%,biotin 1 mg/L,gibberellic acid 3 mg/L.The fermentation conditions were optimized by single-factor design and orthogonal test.The results indicated that the optimal fermentation conditions were original pH 5.5,shaker speed 250 r/min,amount of inoculation 10%,temperature 28℃,time 48 h,and the yield of chitosan was 5.51 g/L.Chitosan was extracted from Actinomucor elegans mycelia using alkali and acid treatments followed by a-amylase treatment.Acid treatments were carried out using acetic,hydrochloric and sulfuric acid,respectively.The highest yields of chitosan were obtained with 1 mol/L NaOH at 121℃ for 30 min and 4%HCl at 95℃ for 6 h and then addition of 4%a-amylase at 90℃ for 2 h,and the percentage of chitosan was 16.91%,the deacetylation and average molecular weight of chitosan were 90.24%,1.38×105.The purity of chitosan was 92.83%measured with alizarin red method.The method for purifying chitosan showed that SDS could remove protein and ash content simultaneously,and the removal rates of protein and ash were up to 83.78%,59%,respectively.FTIR spectra of chitosan indicated that different acids treatment had less influence on the structure of chitosan.