Yu Daobing, Shi Yanke, Wang Qun, Zhang Xin, Zhao Yuhua
College of Forestry and Biotechnology, Zhejiang Agriculture and Forestry University, Lin'an, 311300 Zhejiang People's Republic of China.
College of Life Sciences, Zhejiang University, Hangzhou, 310058 Zhejiang People's Republic of China.
Bioresour Bioprocess. 2017;4(1):35. doi: 10.1186/s40643-017-0166-4. Epub 2017 Jul 27.
Agricultural waste is as an alternative low-cost carbon source or beneficial additives which catch most people's eyes. In addition, methanol and sweet potato vine hydrolysate (SVH) have been reported as the efficient enhancers of fermentation according to some reports. The objective of the present study was to confirm SVH as an efficient additive in CA production and explore the synergistic effects of methanol and SVH in fermentation reactions.
The optimal fermentation conditions resulted in a maximum citric acid concentration of 3.729 g/L. The final citric acid concentration under the optimized conditions was increased by 3.6-fold over the original conditions, 0.49-fold over the optimized conditions without methanol, and 1.8-fold over the optimized conditions in the absence of SVH. Kinetic analysis showed that , , and in the optimized systems were significantly improved compared with those obtained in the absence of methanol or SVH. Further, scanning electron microscopy (SEM) revealed that methanol stress promoted the formation of conidiophores, while SVH could neutralize the effect and prolong Aspergillus niger vegetative growth. Cell viability analysis also showed that SVH might eliminate the harmful effects of methanol and enhance cell membrane integrity.
SVH was a superior additive for organic acid fermentation, and the combination of methanol and SVH displayed a significant synergistic effect. The research provides a preliminary theoretical basis for SVH practical application in the fermentation industry.
农业废弃物作为一种低成本的替代碳源或有益添加剂，备受关注。此外，据一些报道称，甲醇和红薯藤水解物（SVH）是发酵的有效增强剂。本研究的目的是确认SVH是柠檬酸生产中的一种有效添加剂，并探索甲醇和SVH在发酵反应中的协同作用。
最佳发酵条件下柠檬酸的最大浓度为3.729 g/L。优化条件下的最终柠檬酸浓度比原始条件提高了3.6倍，比无甲醇的优化条件提高了0.49倍，比无SVH的优化条件提高了1.8倍。动力学分析表明，与无甲醇或SVH的系统相比，优化系统中的 、 和 均有显著改善。此外，扫描电子显微镜（SEM）显示，甲醇胁迫促进了分生孢子梗的形成，而SVH可以抵消这种影响并延长黑曲霉的营养生长。细胞活力分析还表明，SVH可能消除甲醇的有害影响并增强细胞膜完整性。
SVH是有机酸发酵的优良添加剂，甲醇和SVH的组合显示出显著的协同效应。该研究为SVH在发酵工业中的实际应用提供了初步的理论依据。
