米根霉废菌体制备壳聚糖及其成膜性能
Preparation of Chitosan from Waste Biomass of Rhizopus oryzae and its Membrane Characteristics
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摘要: 以米根霉乳酸发酵废菌体制备壳聚糖,并对其成膜性能进行研究。结果表明,米根霉发酵100 g/L葡萄糖48 h,可获得51.59 g/L的乳酸和4.36 g/L的米根霉菌体,废菌体中可提取壳聚糖占菌体干质量的13.5%。米根霉菌体提取的壳聚糖脱乙酰度89.4%,高于商品壳聚糖的脱乙酰度86.6%。20 g/L的米根霉壳聚糖溶液黏度5.13 mPa·s,重均分子质量(68.61 ku)与螃蟹壳来源的商品壳聚糖重均分子质量(70.17 ku)相近,两者的红外光谱基本一致。厚度为(0.025±0.002)mm壳聚糖膜,米根霉壳聚糖膜和商品壳聚糖膜的弹性模量分别为42.72和14.64 N/mm2,拉伸强度分别为132.31和44.13 N/m,吸水率分别为52.90%和175.80%,最大失重速率温度分别为281.4和285.4 ℃,起始和终止分解温度存在差异。米根霉壳聚糖的成膜性能优于商品壳聚糖,适合于食品包装薄膜的制备。Abstract: Preparation of chitosan from waste biomass of lactic acid fermentation and its membrane characteristics were investigated. The results indicated that 100 g/L of glucose was fermented by R. oryzae for 48 h, then 51.59 g/L of lactic acid and 4.36 g/L of biomass were obtained, and chitosan extraction yield about 13.5 % of the cell dry weight was achieved . The deacetylation degree of R. oryzae chitosan was 89.4%, which was higher than that of commodity chitosan(86.6%). The viscosity of 20 g/L of R. oryzae chitosan solution was 5.13 mPa·s, and the molecular weight of R. oryzae chitosan(Mw=68.61 ku, Mn=48.13 ku) was similar to commodity chitosan(Mw=70.17 ku, Mn=53.53 ku), which was extracted from crab shell. The results of FT-IR proved that the R. oryzae chitosan was similar to commodity chitosan. When the thickness of membrane was (0.025±0.002)mm,the modulus of elasticity of R. oryzae chitosan membrane and commodity chitosan membrane were 42.72 and 14.64 N/mm2, respectively. The tensile strengths were 132.31 and 44.13 N/m, respectively. The water absorption rates were 52.90% and 175.80%, respectively. The temperatures at maixmum decomposition rate were 281.4 ℃ and 285.4 ℃, respectively. The onset and final temperature of decomposition were different. The film-forming performance of R. oryzae chitosan was better than that of commodity chitosan, and the R. oryzae chitosan was suitable for food packaging film preparation.