Research and Development Center of Biorational Pesticides, Northwest A & F University, Yangling, Shaanxi, People's Republic of China.
PLoS One. 2012;7(6):e38421. doi: 10.1371/journal.pone.0038421. Epub 2012 Jun 6.
The production of secondary metabolites with antibiotic properties is a common characteristic to entomopathogenic bacteria Xenorhabdus spp. These metabolites not only have diverse chemical structures but also have a wide range of bioactivities of medicinal and agricultural interests. Culture variables are critical to the production of secondary metabolites of microorganisms. Manipulating culture process variables can promote secondary metabolite biosynthesis and thus facilitate the discovery of novel natural products. This work was conducted to evaluate the effects of five process variables (initial pH, medium volume, rotary speed, temperature, and inoculation volume) on the antibiotic production of Xenorhabdus bovienii YL002 using response surface methodology. A 2(5-1) factorial central composite design was chosen to determine the combined effects of the five variables, and to design a minimum number of experiments. The experimental and predicted antibiotic activity of X. bovienii YL002 was in close agreement. Statistical analysis of the results showed that initial pH, medium volume, rotary speed and temperature had a significant effect (P<0.05) on the antibiotic production of X. bovienii YL002 at their individual level; medium volume and rotary speed showed a significant effect at a combined level and was most significant at an individual level. The maximum antibiotic activity (287.5 U/mL) was achieved at the initial pH of 8.24, medium volume of 54 mL in 250 mL flask, rotary speed of 208 rpm, temperature of 32.0°C and inoculation volume of 13.8%. After optimization, the antibiotic activity was improved by 23.02% as compared with that of unoptimized conditions.
具有抗生素特性的次生代谢产物的产生是昆虫病原细菌 Xenorhabdus spp 的共同特征。这些代谢产物不仅具有多样的化学结构，而且具有广泛的药用和农业生物活性。培养变量对微生物次生代谢产物的产生至关重要。操纵培养过程变量可以促进次生代谢物的生物合成，从而有助于发现新的天然产物。这项工作旨在评估初始 pH 值、培养基体积、转速、温度和接种量等五个过程变量对 Xenorhabdus bovienii YL002 抗生素产生的影响，采用响应面法。选择 2(5-1)因子中心组合设计来确定五个变量的组合效应，并设计出最少数量的实验。X. bovienii YL002 的实验和预测抗生素活性非常吻合。结果的统计分析表明，初始 pH 值、培养基体积、转速和温度在个体水平上对 X. bovienii YL002 的抗生素产生有显著影响（P<0.05）；培养基体积和转速在组合水平上有显著影响，在个体水平上最为显著。在初始 pH 值为 8.24、培养基体积为 54 mL 的 250 mL 瓶中、转速为 208 rpm、温度为 32.0°C 和接种量为 13.8%时，抗生素活性达到最大值（287.5 U/mL）。优化后，抗生素活性比未优化条件提高了 23.02%。
