Abstract

ε-Poly-l-lysine (ε-PL) is used as a natural food preservative which consists of l-lysine units connected. However, due to the expensive culture medium, the production cost of ε-PL remains high. In this study, cheap raw materials cassava starch (CS) and fish meal (FM) were employed by S. albulus FQC-24 for ε-PL production. In the single factor experiment, the maximum ε-PL production reached 0.97 g/L at 60 g/L CS and 15 g/L FM. The results of screening experiments by Plackett–Burman design showed that three main components affecting ε-PL production were CS, FM, and (NH₄)₂SO₄. And the standardized effects of CS, FM, and (NH₄)₂SO₄ were 0.13, −0.22, and −0.2, respectively. The optimum fermentation medium developed by response surface methodology for ε-PL production contained (g/L) CS, 67.56; FM, 14.70 and (NH₄)₂SO₄, 5.41. Under the optimum conditions, the ε-PL production was achieved 1.30 g/L, with 34.02% higher than that before optimization. Moreover, ε-PL productions of batch and fed-batch fermentation in a 7-L fermentor were improved to 2.13 and 17.17 g/L respectively, which increased by 0.64 and 12.2 times compared with the shake flask culture. The results indicated that FM and CS are promising substrates for the efficient production of ε-PL.

摘要

ε-聚-l-赖氨酸（ε-PL）用作天然食品防腐剂，由连接的l-赖氨酸单元组成。然而，由于培养基价格昂贵，ε-PL的生产成本仍然很高。在这项研究中， S.albulus FQC-24使用廉价的原料木薯淀粉 (CS) 和鱼粉 (FM)生产 ε-PL。在单因素实验中，最大 ε-PL 产量在 60 g/L CS 和 15 g/L FM 时达到 0.97 g/L。Plackett-Burman 设计的筛选实验结果表明，影响 ε-PL 产生的三个主要成分是 CS、FM 和 (NH ₄ ) ₂ SO ₄。以及 CS、FM 和 (NH ₄ ) ₂ SO的标准化效应₄分别为 0.13、-0.22 和 -0.2。通过响应面法开发的用于生产 ε-PL 的最佳发酵培养基含有 (g/L) CS，67.56；FM，14.70 和 (NH ₄ ) ₂ SO ₄，5.41。在优化条件下，ε-PL产量达到1.30 g/L，比优化前提高了34.02%。此外，在 7 L 发酵罐中分批和补料分批发酵的 ε-PL 产量分别提高到 2.13 和 17.17 g/L，与摇瓶培养相比分别提高了 0.64 和 12.2 倍。结果表明，FM和CS是高效生产ε-PL的有希望的底物。