产β-甘露聚糖酶菌株的筛选鉴定及产酶条件优化

Screening and identification ofβ-mannanase-producing strains and optimization of enzyme production conditions

为获得产β-甘露聚糖酶菌株,取常年种植魔芋的土壤,通过富集培养与筛选鉴定获得目标菌株,并对其产酶条件进行优化。结果表明,分离到6株可以降解魔芋粉的菌株,其中菌株HKS018产生的降解圈最明显,且酶活最高。对菌株HKS018的16S rDNA基因序列和gyrB基因序列进行扩增,通过序列比对及构建系统发育树,结合形态特征、生理生化特征鉴定菌株HKS018为枯草芽孢杆菌(Bacillus subtilis)。其最优发酵条件为:发酵温度30℃、发酵时间48 h、初始pH值为7.0、接种量1.0%、装液量50 mL/250 mL、转速180 r/min。在此优化条件下,β-甘露聚糖酶酶活为68.28 U/mL,比优化前酶活力提高了5.29倍。

In order to obtainβ-mannanase-producing strains,the soil for planting konjaks all year round was selected,the target strain was obtained by enrichment culture,screening and identification,and the enzyme production conditions were optimized.The results showed that 6 strains which could degrade konjac powder were isolated.Among them,strain HKS018 produced the most obvious degradation cycle and showed the highest enzyme activity.16S rDNA and gyrB gene sequence of strain HKS018 were amplified,the strain HKS018 was identified as Bacillus subtilis through sequence alignment and phylogenetic tree construction combined morphological characteristics,physiological and biochemical characteristics.The optimal fermentation conditions were as follows:temperature 30℃,time 48 h,initial pH 7.0,inoculum 1.0%,liquid volume 50 ml/250 ml,rotation speed 180 r/min.Under these optimized conditions,theβ-mannanase activity was 68.28 U/ml,which was 5.29 times higher than that before optimization.