Improving the biotransformation of phytosterols to 9α-hydroxy-4-androstene-3,17-dione by deleting embC associated with the assembly of cell envelope in Mycobacterium neoaurum

Improving the biotransformation efficiency of soybean phytosterols in Mycolicibacterium neoaurum by the combined deletion of fbpC3 and embC in cell envelope synthesis

“…The change in the transformation efficiency of constructed strains was assessed in the vegetative cell and resting cell conversion systems [ 8 , 14 ]. Briefly, the cells in the suspension culture (0.5 mL) were extracted with the same volume of ethyl acetate (0.5 mL).…”

“…This unique cell envelope leads to a low permeability and forms an effective barrier, which can prevent toxic compounds from entering mycobacterial cells [ 12 , 13 ]. However, the feature negatively affects the uptake of sterol substrates at the bioconversion to steroidal intermediates [ 8 , 14 ]. The deletion of kasB encoding a β -ketoacyl-acyl carrier protein synthase likely shortened the length of keto-mycolic acids, the key components of mycolic acid methyl esters (MAMEs) in the core m-AG-PG structure [ 8 ].…”

“…The deletion of kasB encoding a β -ketoacyl-acyl carrier protein synthase likely shortened the length of keto-mycolic acids, the key components of mycolic acid methyl esters (MAMEs) in the core m-AG-PG structure [ 8 ]. Moreover, the inactivation of arabinofuranosyltransferase gene embC caused a synthesis defect of the lipoarabinomannan from lipomannan [ 14 , 15 ]. The above two changes remarkably improved the cell permeability and enhanced the uptake of steroids.…”

“…Since the fbp genes are likely synthetically lethal, the double deletion of them has not been reported [ 26 ]. It is necessary to evaluate the effects of the serial deletion of identified target genes involved in cell envelope synthesis of M. neoaurum [ 8 , 14 ]. As a consequence of these combined manipulations, the biotransformation efficiency of soybean phytosterols by the mutant strain might be boosted up to a new level.…”

“…Then, the biotransformation efficiency of soybean phytosterols in the fbpC3 -deficient 9-OHAD-producing M. neoaurum strain was measured. Finally, the combined manipulation of the previously screened gene targets that influenced the accumulation of steroidal intermediates [ 8 , 14 ] and the newly identified fbpC3 was performed to further increase 9-OHAD yield.…”