寄生沙棘木蠹蛾的白僵菌菌株特性及其胞外蛋白酶、几丁质酶的活性

Characteristics and extracellular protease and chitinase activity of Beauveria bassiana isolated from Holcocerus hippophaecolus

［目的］ 明确寄生沙棘木蠹蛾的白僵菌不同菌株的生物学特性，以筛选优良菌种加以利用。［方法］ 测定温湿度对分离自沙棘木蠹蛾幼虫和蛹的5株白僵菌菌株分生孢子萌发的影响，并采用平板测定法和Lowry及DNS测定法对白僵菌各菌株胞外蛋白酶和几丁质酶活性进行测定。［结果］ 白僵菌SJ01、SJ02、SJ03、SJ04、SJ05菌株在15～35 ℃范围内均可萌发，15、20 ℃和35 ℃时孢子萌发率相对较低，25 ℃时5株菌株萌发率均高，为90％～98％。相对湿度为41％、50％和61％时，各菌株均不萌发；76％和80％时，SJ05的萌发率明显高于其他菌株，分别达60％和80％。50 ℃高温胁迫24 min和30 min后，各菌株萌发率均显著降低，几乎不萌发。胁迫12 min和18 min后，SJ05的萌发率较其他菌株高，表明其抗高温性强。5株菌株均可产生胞外蛋白酶和几丁质酶，其中SJ05菌株胞外蛋白酶产量为55.3 U/mL,几丁质酶产量为137.9 U/mL,其蛋白酶和几丁质酶活性均显著高于其他菌株。［结论］ SJ05菌株具有较强的耐热性，一定的抗低湿能力，较高的蛋白酶和几丁质酶活性，为最优菌株。

[Objective] To specify the biological characteristics of Beauveria bassiana isolated from the infected larvae and pupae of Holcocerus hippophaecolus from different areas, and screen superior isolates for potential use.[Method] The influences of temperature and humidity on spore germination of five isolates of B. bassiana infected with the larvae and pupae of H. hippophaecolus were tested. Extracellular protease and chitinase activity of five isolates of B. bassiana were tested by plate determination method, Lowry and DNS determination methods.[Result] All of the isolates could germinate under the temperature of 15-35 ℃. But the germination rates of 5 isolates were relatively low at 15 ℃, 20 ℃ and 35 ℃, and relatively high at 25 ℃. The germination rates varied from 90% to 98% among the isolates, and SJ5 had higher rate （98%）. The isolates could not germinate at the relative humidity of 41%, 50% and 61%. The germination rate of SJ05 isolate could reach to 60% and 80% at the relative humidity of 76% and 80%, remarkably higher than that of the others. High temperature could decrease the germination of the spores. All isolates could not germinate when treated at 50 ℃ for 24 min and 30 min. But SJ05 isolate germinated better than the others after 12 min and 18 min of 50 ℃ temperature treatment. All isolates generated extracellular protease and chitinase, but the activity of both enzymes were significantly different among the isolates. Extracellular protease and chitinase production of SJ05 isolate reached to 55.3 U/mL and 137.9 U/mL, respectively. The activity of extracellular protease and chitinase of SJ05 isolate were higher than that of the others.[Conclusion] SJ05 isolate was the optimal strain with higher heat resistance, ability of lowhumidity resistance and higher protease and chitinase activity.