高产新型淀粉酶菌株MS5.1的选育\=及最适产酶条件

从原筛选的产酶菌株芽 孢杆菌 (Bacillus Stearophilus) BS3.232出发， 经亚硝基胍多次诱变、 初筛和复筛后 ， 获得了产酶水平明显提高的变异菌株MS5.1， 其产酶水平为原株的 153.8%. 薄层分析证 明， 该酶能催化淀粉的水解和转苷， 产物为异麦芽低聚糖， 包括异麦芽糖、 潘糖、 异 麦芽三糖和异麦芽四糖. 表明MS5.1产生的新型淀粉酶能有效地转化淀粉产生异麦芽低聚糖. 用正交法确定了MS5.1菌株的最适产酶条件： 通气量在60%以上， 55 ℃培养24 h. 实验结果表明， 培养温度是影响产酶水平的最主要因素.

Mutagenesis of Bacillus Stearothermophilus MS5.1 and Its Optimum Fermentation Condition

This paper reports a mutagenic strain MS5.1, a strain, mutagenised from an original strain Bacillus stearothermophilus BS3.232 by N-methyl- N′-nitro-N-nitrosoguanidine(NTG), which effectively secreted a new kind of enzy me(neoamylase) that can catalytically make starch into isomalto-oligosaccharide. The activity of MS　5.1 producing enzyme is increased by 53.8% compared with BS3.232 under the same conditions. The results of thin-layer chromatography of the prod ucts from starch catalyzed by the enzyme demonstrated that the enzyme can be used to produce iso maltooligosaccharide from starch, including isomaltose, panose, isomaltotriose, isomaltotetose. The optimum conditions which secreted neoamylase were confirmed by orthogonal test and the results showed that the most important par ameter is the temperature of fermentation and the optimum conditions to secrete the enzyme were: the strain MS5.1 should be cultured with superior to 60% aerati on under 55 ℃ for 24 h.