This study aimed to characterize, evaluate toxicity and optimize the conditions for the growth and production of bacteriocin-like substances by Lactobacillus curvatus P99. The antibacterial activity of the cell-free supernatant (CFS) containing bacteriocin-like substances was evaluated by the agar diffusion technique. The stability of the CFS was also examined after heat treatment, refrigeration, freezing, pH variations, and treatment with different chemical substances. The toxic effect of CFS on Drosophila melanogaster diet was determined by calculating the survival rate of the flies. The effects of pH, temperature, and incubation time were the parameters used to optimize cell growth and production of bacteriocin-like substances through response surface methodology. The CFS was stable for 36 weeks under freezing and refrigeration, as well as under heat treatment, in acidic and basic pH and for all chemical substances tested. Fewer than 50,000 AU/mL of CFS added to D. melanogaster diet showed no toxic effect. The optimum growth condition was pH 6.3 at 29.3 °C for 18.6 h, and the optimum production of bacteriocin-like substances was under pH 6.22 at 30.6 °C for 17.9 h. The data on the optimization of cell growth and the characterization and optimization of bacteriocin-like substances provided information to support the industrial-scale production of this microorganism and its metabolites.

中文翻译：

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曲霉杆菌生长和生产类细菌素的特性，毒性和优化。

这项研究旨在表征，评估毒性和优化条件的生长和生产条件的曲霉乳杆菌P99的细菌素样物质。通过琼脂扩散技术评价了含有细菌素样物质的无细胞上清液（CFS）的抗菌活性。在热处理，冷藏，冷冻，pH变化以及使用不同化学物质处理之后，还检查了CFS的稳定性。CFS对黑腹果蝇的毒性作用通过计算果蝇的成活率来确定饮食。pH，温度和孵育时间的影响是通过响应表面方法优化细胞生长和细菌素样物质产生的参数。CFS在冷冻和冷藏以及热处理，酸性和碱性pH以及所有测试的化学物质下均稳定36周。添加到黑腹果蝇中的CFS少于50,000 AU / mL饮食未显示毒性作用。最佳的生长条件是在29.3°C的pH 6.3下持续18.6 h，而细菌素样物质的最佳生产在30.6°C的pH 6.22上持续17.9 h。细胞生长的优化以及细菌素样物质的表征和优化的数据为支持该微生物及其代谢产物的工业规模生产提供了信息。