新一代糖化酶高产菌株的选育及其工业应用

【目的】建立对糖化酶生产菌种黑曲霉随机突变文库进行筛选的方法,以获得糖化酶酶活提高的突变菌株。【方法】以一株可产糖化酶的黑曲霉菌株Aspergillus niger X1为出发菌株,经硫酸二乙酯诱变获得突变文库,采用葡萄糖的结构类似物——2-脱氧葡萄糖进行筛选,并在筛选过程中逐渐提高2-脱氧葡萄糖浓度,定向选育具有2-脱氧葡萄糖抗性、高产糖化酶的突变株。【结果】获得的高产突变菌株DG36摇瓶发酵糖化酶产量比出发菌株A.niger X1提高22.2%–33.8%,经工业水平50 m~3罐发酵测试,突变株DG36发酵128 h糖化酶活可达49094 U/m L,在相同发酵时间内,其酶活较出发菌株A.niger X1提高32.8%,发酵时间缩短16.9%。【结论】本研究开发了一种以2-脱氧葡萄糖为抗性标记选育高产糖化酶突变株的方法,所得突变株DG36遗传性状稳定,与出发菌相比具有菌丝粗壮、产酶期提前、糖化酶活高、发酵时间短、有利于发酵后处理的优点。

Screening of high-glucoamylase-producing strain of Aspergillus niger with 2-deoxyglucose resistance and the industrial application

Objective] To obtain mutants of Aspergillus niger with high glucoamylase activity, we developed a screening method. Methods] We mutagenized the starting strain A. niger X1 using diethyl sulfate, then cultured the mutant library on agar plate containing 2-deoxyglucose. By increasing the concentration of 2-deoxyglucose, we obtained mutants with high resistance to 2-deoxyglucose and then studied glucoamylase activities. Results] In shake flask fermentation, glucoamylase activity of the mutant strain A. niger DG36 increased by 22.2% to 33.8%. In a 50 m³ fermenter, glucoamylase activity of the strain DG36 reached up to 49094 U/mL at 128 h, 32.8% higher than that of the starting strain A. niger X1. As a result, the fermentation period of the strain DG36 was reduced by 16.9% compared with A. niger X1. Conclusion] Mutant strain DG36 exhibited higher glucoamylase activity, shorter fermentation period and more suitable for the purification treatment than the starting strain A. niger X1.