Xiong Liang-Bin, Liu Hao-Hao, Xu Li-Qin, Wei Dong-Zhi, Wang Feng-Qing
State Key Laboratory of Bioreactor Engineering, Newworld Institute of Biotechnology, East China University of Science and Technology , Shanghai, China.
J Agric Food Chem. 2017 Jan 25;65(3):626-631. doi: 10.1021/acs.jafc.6b05314. Epub 2017 Jan 12.
9α-Hydroxy-4-androstene-3,17-dione (9-OHAD) is a valuable steroid pharmaceutical intermediate which can be produced by the conversion of soybean phytosterols in mycobacteria. However, the unsatisfactory productivity and conversion efficiency of engineered mycobacterial strains hinder their industrial applications. Here, a sigma factor D (sigD) was investigated due to its dramatic downregulation during the conversion of phytosterols to 9-OHAD. It was determined as a negative regulator in the metabolism of phytosterols, and the deletion of sigD in a 9-OHAD-producing strain significantly enhanced the titer of 9-OHAD by 18.9%. Furthermore, a high yielding strain was constructed by the combined modifications of sigD and choM2, a key gene in the phytosterol metabolism pathway. After the modifications, the productivity of 9-OHAD reached 0.071 g/L/h (10.27 g/L from 20 g/L phytosterol), which was 22.5% higher than the original productivity of 0.058 g/L/h (8.37 g/L from 20 g/L phytosterol) in the industrial resting cell biotransformation system.
9α-羟基-4-雄烯-3,17-二酮（9-OHAD）是一种有价值的甾体药物中间体，可通过分枝杆菌中大豆植物甾醇的转化来生产。然而，工程化分枝杆菌菌株的生产力和转化效率不尽人意，阻碍了它们的工业应用。在此，对σ因子D（sigD）进行了研究，因为在植物甾醇转化为9-OHAD的过程中它显著下调。它被确定为植物甾醇代谢中的负调节因子，在一株生产9-OHAD的菌株中缺失sigD可使9-OHAD的产量显著提高18.9%。此外，通过对sigD和植物甾醇代谢途径中的关键基因choM2进行联合修饰构建了一株高产菌株。修饰后，9-OHAD的生产力达到0.071 g/L/h（由20 g/L植物甾醇产生10.27 g/L），比工业静止细胞生物转化系统中原来的生产力0.058 g/L/h（由20 g/L植物甾醇产生8.37 g/L）高出22.5%。
