Entomology Research Laboratory, Plant and Soil Science, University of Vermont, 661 Spear Street, Burlington, VT 05405-0105, USA.
J Microbiol Biotechnol. 2011 Jun;21(6):604-12.
Beauveria bassiana SFB-205 supernatant can effectively control cotton aphid populations, which is closely associated with its chitinase activity. The present work extends to optimizing a culture medium to produce more efficacious supernatant in flask conditions, followed by scale-up in 7 L, 300 L and 1.2 KL fermentors with the parameter of chitinase. In flask conditions, a combination of soluble starch and yeast extract produced the greatest amount of chitinase (5.1 units/ml) and its supernatant had the highest aphicidal activity. An optimal quantitative combination of the two substrates, estimated by a response surface method, enabled the supernatant to have 15.7 units/ml of chitinase activity and 3.7 ml/l of median lethal concentration (LC50) of toxicity against cotton aphid adults in laboratory conditions. In the scale-up conditions, overall supernatant had 25-28 units/ml of chitinase activity. Decrease in pH and limitation of dissolved oxygen (DO) during cultures were significantly related to the yield of chitinase. These results suggest that the substrate-dependent chitinase production can be background information for optimizing a culture medium, and pH and DO are critical factors in maximizing the production in scale-up conditions.
球孢白僵菌 SFB-205 上清液能有效控制棉蚜种群，这与其几丁质酶活性密切相关。本研究扩展到优化培养基，以在摇瓶条件下生产更有效的上清液，然后在 7L、300L 和 1.2KL 发酵罐中进行规模放大，并以几丁质酶为参数。在摇瓶条件下，可溶性淀粉和酵母提取物的组合产生了最多的几丁质酶（5.1 单位/ml），其上清液具有最高的杀蚜活性。通过响应面法估计的两种底物的最佳定量组合，使上清液在实验室条件下对棉蚜成虫的几丁质酶活性达到 15.7 单位/ml，半数致死浓度（LC50）达到 3.7ml/L。在放大条件下，总上清液中的几丁质酶活性为 25-28 单位/ml。培养过程中 pH 值的降低和溶解氧（DO）的限制与几丁质酶的产量显著相关。这些结果表明，几丁质酶的产生与底物有关，可以作为优化培养基的背景信息，而 pH 值和 DO 是在放大条件下最大限度提高产量的关键因素。
