Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Stuttgart, Germany.
Microb Cell Fact. 2024 Sep 30;23(1):260. doi: 10.1186/s12934-024-02531-w.
The production of surfactin, an extracellular accumulating lipopeptide produced by various Bacillus species, is a well-known representative of microbial biosurfactant. However, only limited information is available on the correlation between the growth rate of the production strain, such as B. subtilis BMV9, and surfactin production. To understand the correlation between biomass formation over time and surfactin production, the availability of glucose as carbon source was considered as main point. In fed-batch bioreactor processes, the B. subtilis BMV9 was used, a strain well-suited for high cell density fermentation. By adjusting the exponential feeding rates, the growth rate of the surfactin-producing strain, was controlled.
Using different growth rates in the range of 0.075 and 0.4 h, highest surfactin titres of 36 g/L were reached at 0.25 h with production yields Y of 0.21 g/g and Y of 0.7 g/g, while growth rates lower than 0.2 h resulted in insufficient and slowed biomass formation as well as surfactin production (Y of 0.11 g/g and Y of 0.47 g/g for 0.075 h). In contrast, feeding rates higher than 0.25 h led to a stimulation of overflow metabolism, resulting in increased acetate formation of up to 3 g/L and an accumulation of glucose due to insufficient conversion, leading to production yields Y of 0.15 g/g and Y of 0.46 g/g for 0.4 h.
Overall, the parameter of adjusting exponential feeding rates have an important impact on the B. subtilis productivity in terms of surfactin production in fed-batch bioreactor processes. A growth rate of 0.25 h allowed the highest surfactin production yield, while the total conversion of substrate to biomass remained constant at the different growth rates.
表面活性剂是一种由各种芽孢杆菌产生的胞外积累型脂肽，是微生物生物表面活性剂的典型代表。然而，关于生产菌株（如枯草芽孢杆菌 BMV9）的生长速率与表面活性剂生产之间的相关性，仅有有限的信息。为了了解生物量随时间的形成与表面活性剂生产之间的相关性，将葡萄糖作为碳源的可用性作为主要关注点。在补料分批生物反应器工艺中，使用了枯草芽孢杆菌 BMV9 菌株，该菌株非常适合高密度发酵。通过调整指数进料速率，控制了表面活性剂生产菌株的生长速率。
在 0.075 和 0.4 h 的生长速率范围内，采用不同的生长速率，在 0.25 h 时达到了 36 g/L 的最高表面活性剂产量，产率 Y 为 0.21 g/g 和 0.7 g/g，而生长速率低于 0.2 h 会导致生物量形成不足和缓慢，以及表面活性剂生产减少（0.075 h 时的产率 Y 为 0.11 g/g 和 0.47 g/g）。相反，进料速率高于 0.25 h 会刺激溢出代谢，导致高达 3 g/L 的乙酸盐形成增加，以及由于转化不足而积累葡萄糖，导致产率 Y 为 0.15 g/g 和 0.46 g/g 在 0.4 h 时。
总体而言，调整指数进料速率的参数对补料分批生物反应器工艺中枯草芽孢杆菌生产表面活性剂的生产力具有重要影响。生长速率为 0.25 h 时，表面活性剂的产率最高，而在不同的生长速率下，基质到生物量的总转化率保持不变。
