Science Center for Future Foods, Jiangnan University, Wuxi, 214122, China.
Qingdao Vland Biotech Group Co., Ltd, Qingdao, 266000, China.
BMC Microbiol. 2023 Apr 26;23(1):117. doi: 10.1186/s12866-023-02838-5.
Surfactin produced by microbial fermentation has attracted increasing attention because of its low toxicity and excellent antibacterial activity. However, its application is greatly limited by high production costs and low yield. Therefore, it is important to produce surfactin efficiently while reducing the cost. In this study, B. subtilis strain YPS-32 was used as a fermentative strain for the production of surfactin, and the medium and culture conditions for the fermentation of B. subtilis YPS-32 for surfactin production were optimized.
First, Landy 1 medium was screened as the basal medium for surfactin production by B. subtilis strain YPS-32. Then, using single-factor optimization, the optimal carbon source for surfactin production by B. subtilis YPS-32 strain was determined to be molasses, nitrogen sources were glutamic acid and soybean meal, and inorganic salts were KCl, KHPO, MgSO, and Fe(SO). Subsequently, using Plackett-Burman design, MgSO, time (h) and temperature (°C) were identified as the main effect factors. Finally, Box-Behnken design were performed on the main effect factors to obtain optimal fermentation conditions: temperature of 42.9 °C, time of 42.8 h, MgSO = 0.4 g·L. This modified Landy medium was predicted to be an optimal fermentation medium: molasses 20 g·L, glutamic acid 15 g·L, soybean meal 4.5 g·L, KCl 0.375 g·L, KHPO 0.5 g·L, Fe(SO) 1.725 mg·L, MgSO 0.4 g·L. Using the modified Landy medium, the yield of surfactin reached 1.82 g·L at pH 5.0, 42.9 ℃, and 2% inoculum for 42.8 h, which was 2.27-fold higher than that of the Landy 1 medium in shake flask fermentation. Additionally, under these optimal process conditions, further fermentation was carried out at the 5 L fermenter level by foam reflux method, and at 42.8 h of fermentation, surfactin reached a maximum yield of 2.39 g·L, which was 2.96-fold higher than that of the Landy 1 medium in 5 L fermenter.
In this study, the fermentation process of surfactin production by B. subtilis YPS-32 was improved by using a combination of single-factor tests and response surface methodology for test optimization, which laid the foundation for its industrial development and application.
微生物发酵生产的表面活性剂因毒性低、抗菌活性好而备受关注。然而，其应用受到高生产成本和低产量的极大限制。因此，高效生产表面活性剂的同时降低成本非常重要。本研究以枯草芽孢杆菌 YPS-32 为发酵菌株，对其发酵生产表面活性剂的培养基和培养条件进行优化。
首先，筛选出 Landy1 培养基作为枯草芽孢杆菌 YPS-32 生产表面活性剂的基础培养基。然后，通过单因素优化，确定枯草芽孢杆菌 YPS-32 生产表面活性剂的最佳碳源为糖蜜，氮源为谷氨酸和豆粕，无机盐为 KCl、KH2PO4、MgSO4 和 Fe(SO4)3。随后，利用 Plackett-Burman 设计确定 MgSO4、时间（h）和温度（℃）为主要影响因素。最后，对主要影响因素进行 Box-Behnken 设计，得到最佳发酵条件：温度 42.9℃，时间 42.8h，MgSO4=0.4g·L-1。预测改良后的 Landy 培养基为最佳发酵培养基：糖蜜 20g·L-1，谷氨酸 15g·L-1，豆粕 4.5g·L-1，KCl 0.375g·L-1，KH2PO4 0.5g·L-1，Fe(SO4)3 1.725mg·L-1，MgSO4 0.4g·L-1。在改良后的 Landy 培养基中，在 pH5.0、42.9℃、2%接种量条件下发酵 42.8h，表面活性剂产量达到 1.82g·L-1，摇瓶发酵产量比 Landy1 培养基提高 2.27 倍。此外，在最佳工艺条件下，采用泡沫回流法在 5L 发酵罐中进行进一步发酵，发酵 42.8h 时，表面活性剂产量达到 2.39g·L-1，比 5L 发酵罐中 Landy1 培养基提高 2.96 倍。
本研究通过单因素试验和响应面法对枯草芽孢杆菌 YPS-32 生产表面活性剂的发酵工艺进行了优化，为其工业化发展和应用奠定了基础。
