出芽短梗霉产普鲁兰多糖除菌及脱蛋白工艺

Sterilization and Deproteinization Process of Pullulan Produced by Aureobasidium pullulans

普鲁兰多糖是出芽短梗霉(Aureobasidium pullulans)发酵产生的一种胞外多糖,由于它黏度大导致菌液分离困难,同时国家标准对产品中蛋白含量有严格的要求,因此对有效的菌体分离和脱蛋白的工艺进行探究具有重要的意义。采用生物高分子絮凝除菌和蛋白酶脱蛋白的方法,分别从4种絮凝剂和6种蛋白酶中优化筛选絮凝剂和蛋白酶,结果表明:壳聚糖絮凝除菌效果最好,碱性蛋白酶脱蛋白效率最好。通过单因素试验和响应面试验优化絮凝除菌和脱蛋白工艺。得到最佳除菌条件:pH值为3.7、絮凝时间为20 min、絮凝温度为40℃、壳聚糖添加量为0.96 g/L,此时除菌率为99.19%,多糖得率为91.3%;最佳脱蛋白条件:pH值为8.6、酶解温度为45℃、酶解时间为2.5 h,碱性蛋白酶添加量为83 U/mL,此时脱蛋白率为74.70%,多糖得率为98.42%。经过这一优化除菌、脱蛋白工艺,产品中蛋白含量为0.045%,达到国家标准要求,再经传统的脱色、超滤浓缩、干燥、产品纯度为91.5%。

Pullulan is an extracellular polysaccharide produced by Aureobasidium pullulans fermentation.Due to its high viscosity,pullulan is difficult to be separated from the fermentation medium,and the Chinese national standard has a strict requirement on the protein content of its product.Therefore,it is significant to find an effective process for bacterial separation and deproteinization.Biopolymer flocculation and protease deproteinization methods were used to optimize and screen the optimal flocculation and protease from four flocculants and six proteases.The results indicated that chitosan and alkaline protease were preferable in sterilization and deproteinization,respectively.The sterilization and deproteinization techniques were optimized by the single factor experiment and response surface test.The results showed that the optimum sterilization conditions were as follows:pH3.7,flocculation time of 20 min,flocculation temperature of 40℃,and chitosan addition of 0.96 g/L,which resulted in the sterilization rate of 99.19%and the polysaccharide yield of 91.3%.The optimum deproteinization conditions were as follows:pH8.6,enzymolysis time of 2.5 h,enzymolysis temperature of 45℃,and alkaline protease addition of 83 U/mL,which resulted in the deproteinization rate of 74.70%and the polysaccharide yield of 98.42%.With the optimized sterilization and deproteinization processes,the protein content of the product was 0.045%,meeting the requirements of the national standard.The purity of the product reached 91.5%after traditional decolorization,ultrafiltration,concentration,and drying.