Commercial products based on Trichoderma are obtained mainly from solid-state fermentation. Submerged liquid fermentation is the most appropriate method compared to the solid medium for large-scale production of Trichoderma spp. The present study aimed to optimize the combination of key variables that influence the liquid fermentation process of Trichoderma asperelloides LQC-96 for conidial production coupled with its efficiency in the control of Sclerotinia sclerotiorum. In addition, we verified whether the optimized culture conditions can be used for the conidial production of Trichoderma erinaceum T-12 and T-18 and Trichoderma harzianum T-15. Fermentation studies were performed in shake flasks following a planned experimental design to reduce the number of tests and consumable costs. The effect of temperature, pH, photoperiod, carbon:nitrogen ratio and water activity on conidial production were assessed, which of pH was the only meaningful factor contributing to increased conidial production of T. asperelloides LQC-96. From the five variables studied initially, pH and C:N ratio were further used in the second design (rotational central composite design-RCCD). Hence, the best conditions for the production of T. asperelloides LQC-96 conidia by liquid fermentation consisted of initial pH of 3.5, C:N ratio of 200:1 at 30 °C, without glycerol, and under 24 h photoperiod. The highest conidial concentration was observed after seven days of fermentation. Under these optimal conditions, T. erinaceum T-12 and T-18, and T. harzianum T-15 were also cultivated, but only LQC-96 efficiently parasitized S. sclerotiorum, precluding sclerotium myceliogenic germination. Our findings propose optimal fermentation conditions that maximize conidial production of T. asperelloides as a potential biofungicide against S. sclerotiorum.

中文翻译：

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深层液体发酵优化曲霉木霉的大规模生产及其对核盘菌的拮抗作用

基于木霉属的商业产品主要通过固态发酵获得。与固体培养基相比，深层液体发酵是大规模生产木霉属的最合适方法。本研究旨在优化影响曲霉 LQC-96 液体发酵过程的关键变量组合，用于分生孢子生产及其控制核盘菌的效率。此外，我们验证了优化的培养条件是否可以用于木霉T-12和T-18以及哈茨木霉T-15的分生孢子生产。按照计划的实验设计在摇瓶中进行发酵研究，以减少测试次数和消耗品成本。温度、pH、光周期、碳的影响：评估了氮比和水分活度对分生孢子生产的影响，哪个 pH 值是导致 T. asperelloides LQC-96 分生孢子生产增加的唯一有意义的因素。根据最初研究的五个变量，在第二个设计（旋转中心复合设计-RCCD）中进一步使用了 pH 值和 C:N 比。因此，通过液体发酵生产 T. asperelloides LQC-96 分生孢子的最佳条件包括初始 pH 值为 3.5、C:N 比为 200:1、30 °C、无甘油和 24 小时光周期。在发酵 7 天后观察到最高分生孢子浓度。在这些最佳条件下，T. erinaceum T-12 和 T-18 以及 T. harzianum T-15 也被培养，但只有 LQC-96 有效地寄生在 S. sclerotiorum，阻止了菌核菌丝体的萌发。