The conversion of low value-added phytosterols into 9α-hydroxy-4-androstene-3,17-dione (9-OHAD) by mycobacteria is an important step in the steroid pharmaceutical industry. However, the highly dense cell envelope with extremely low permeability largely affects the overall transformation efficiency. Here, we preliminarily located the key gene embC required for the synthesis of lipoarabinomannan from lipomannan in Mycobacterium neoaurum. The genetic manipulation of embC indicated that it might be the only functional enzyme catalyzing the above synthesis process. The deficiency of lipoarabinomannan led to a significantly increased cell permeability, which in turn caused the enhanced uptake capacity of cells. The sterol substrate conversion efficiency of mycobacterial cells was increased by about 52.4% after 72-h conversion. Ultimately, the absence of embC increased the productivity from 0.0927 g/L/h to 0.1031 g/L/h, as confirmed by a resting cell system. This study verified the feasibility of improving the efficiency of the microbial conversion system through the cell envelope engineering strategy.

分枝杆菌将低附加值的植物甾醇转化为 9α-羟基-4-雄甾烯-3,17-二酮 (9-OHAD) 是类固醇制药行业的重要一步。然而，具有极低渗透性的高密度细胞包膜在很大程度上影响了整体转化效率。在这里，我们初步定位了新金分枝杆菌中脂甘露聚糖合成脂阿拉伯甘露聚糖所需的关键基因embC。embC的基因操作表明它可能是催化上述合成过程的唯一功能性酶。脂阿拉伯甘露聚糖的缺乏导致细胞通透性显着增加，进而导致细胞摄取能力增强。分枝杆菌细胞的甾醇底物转化效率在转化 72 小时后提高了约 52.4%。最终，正如静息细胞系统所证实的那样，没有embC将生产率从 0.0927 g/L/h 提高到 0.1031 g/L/h。本研究验证了通过细胞包膜工程策略提高微生物转化系统效率的可行性。