Key Laboratory of Systems Bioengineering, Ministry of Education and Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
OMICS. 2012 Jul-Aug;16(7-8):387-96. doi: 10.1089/omi.2011.0047. Epub 2012 Jun 26.
Ketogulonigenium vulgare has long been used in industry to produce 2-keto-L-gulonic acid (2KGA), the precursor of vitamin C. This fermentation process involves co-culture of K. vulgare and a Bacillus species. Early studies demonstrated that the presence of the Bacillus strain can enhance the cellular growth and 2KGA production of K. vulgare. However, the molecular mechanism behind how Bacillus affects the growth of K. vulgare and 2KGA production remains unclear. In addition, the inclusion of Bacillus in the fermentation process presents difficulties for the post-separation and purification of 2KGA. To address these issues, efforts have been made to replace the Bacillus strain with chemical compounds. In this study, we found that adding thiol compounds such as reduced glutathione (GSH) and dithiothreitol (DTT) to the K. vulgare mono-culture system can increase the growth of K. vulgare about twofold, and increase 2KGA production by about fivefold. The effects of thiols on the concentrations of some cellular metabolites were determined using gas chromatography coupled to time-of-flight mass spectrometry. The results showed that the levels of intracellular amino acids and intermediates in the pentose phosphate pathway increased significantly after thiol addition. Interestingly, when GSH was added, the levels of key intracellular metabolites in primary metabolic pathways and the cell biomass both reached their maximum in the first 36 h, and then decreased when the thiol was exhausted. These findings indicate that cell growth needs the assistance of a high concentration of thiols. This study is the first report that chemically defined compounds were used to enhance the growth of K. vulgare and 2KGA production. Furthermore, it also provides new insights into the possible cellular interaction between Bacillus species and K. vulgare.
黄色糖多孢菌长期以来一直被用于工业生产 2-酮基-L-古龙酸（2KGA），这是维生素 C 的前体。这种发酵过程涉及黄色糖多孢菌和芽孢杆菌属的共培养。早期研究表明，芽孢杆菌菌株的存在可以增强黄色糖多孢菌的细胞生长和 2KGA 的生产。然而，芽孢杆菌如何影响黄色糖多孢菌的生长和 2KGA 生产的分子机制仍不清楚。此外，芽孢杆菌在发酵过程中的存在给 2KGA 的后分离和纯化带来了困难。为了解决这些问题，人们努力用化学化合物替代芽孢杆菌菌株。在这项研究中，我们发现向黄色糖多孢菌的单培养系统中添加巯基化合物，如还原型谷胱甘肽（GSH）和二硫苏糖醇（DTT），可以使黄色糖多孢菌的生长增加约两倍，并使 2KGA 的产量增加约五倍。使用气相色谱-飞行时间质谱联用技术测定巯基对一些细胞代谢物浓度的影响。结果表明，添加巯基后，细胞内氨基酸和戊糖磷酸途径中间产物的水平显著增加。有趣的是，当添加 GSH 时，主要代谢途径中的关键细胞内代谢物水平和细胞生物量在 36 小时内达到最大值，然后当巯基耗尽时下降。这些发现表明细胞生长需要高浓度巯基的帮助。这项研究首次报道了使用化学定义的化合物来增强黄色糖多孢菌的生长和 2KGA 的生产。此外，它还为芽孢杆菌属和黄色糖多孢菌之间可能的细胞相互作用提供了新的见解。
