School of Chemistry and Life Sciences, Suzhou University of Science and Technology, Suzhou, 215009, Jiangsu, People's Republic of China.
Bioprocess Biosyst Eng. 2022 Aug;45(8):1407-1419. doi: 10.1007/s00449-022-02755-3. Epub 2022 Jul 24.
The production of ε-poly-L-lysine (ε-PL) from cassava bagasse hydrolysate (CBH) by Streptomyces albulus US3-18 was investigated in this study. With 30 g/L glucose from CBH, 1.30 g/L ε-PL and 10.68 g/L biomass were obtained in shake flask fermentation. Interestingly, the two values were increased by 14.0% and 21.5%, respectively, compared to the control (1.14 g/L and 8.79 g/L). Simultaneously, the activities of four key enzymes of ε-PL synthesis during CBH fermentation were enhanced to varying degrees. In batch fermentation of 5-L bioreactor, 3.39 g/L ε-PL and 10.17 g/L DCW were harvested with 40 g/L glucose from CBH. The combination of fed-batch fermentation with two-stage pH strategy significantly increased ε-PL titer and biomass to 37.41 g/L and 41.0 g/L, respectively. Moreover, eleven volatile components were detected in CBH by GC-MS, and 6-pentyl-α-pyrone (6PP) was first identified as the most abundant volatile ingredient. The results in CBH fermentation demonstrated that S. albulus US3-18 exhibited high tolerance to these volatile byproducts. Using ICP-MS, the calcium concentration in CBH was determined as 195.0 mg/(kg hydrolyzate), and cobalt, copper, lead, chromium, mercury and arsenic were not detected. By adding 0.05 g/L CaCl to M3G medium, ε-PL yield was improved by 28.0%, indicating calcium was one of the factors for the enhanced ε-PL production. The study provides a reference for the efficient production of ε-PL from low-cost agricultural residues.
本研究考察了 Streptomyces albulus US3-18 利用木薯渣水解液（CBH）生产 ε-聚赖氨酸（ε-PL）的情况。以 CBH 中的 30g/L 葡萄糖为底物，摇瓶发酵可获得 1.30g/L ε-PL 和 10.68g/L 生物量，与对照（1.14g/L 和 8.79g/L）相比，分别提高了 14.0%和 21.5%。同时，CBH 发酵过程中 ε-PL 合成的四种关键酶的活性也得到不同程度的增强。在 5L 生物反应器分批发酵中，以 CBH 中的 40g/L 葡萄糖为底物，可获得 3.39g/L ε-PL 和 10.17g/L DCW。补料分批发酵与两段 pH 策略相结合，可将 ε-PL 产量和生物量分别提高到 37.41g/L 和 41.0g/L。此外，通过 GC-MS 检测到 CBH 中有 11 种挥发性成分，其中 6-戊基-α-吡喃酮（6PP）首次被鉴定为最丰富的挥发性成分。在 CBH 发酵中，结果表明 S. albulus US3-18 对这些挥发性副产物具有较高的耐受性。通过 ICP-MS 测定，CBH 中的钙浓度为 195.0mg/（kg 水解液），未检测到钴、铜、铅、铬、汞和砷。在 M3G 培养基中添加 0.05g/L CaCl2 可使 ε-PL 产量提高 28.0%，表明钙是提高 ε-PL 产量的因素之一。本研究为利用低成本农业废弃物高效生产 ε-PL 提供了参考。
