Immobilization of rough morphotype Mycolicibacterium neoaurum R for androstadienedione production

Abstract

Objectives Enhance androstadienedione (Androst-1,4-diene-3,17-dione, ADD) production of rough-type morphotype Mycolicibacterium neoaurum variant by repeated-batch fermentation of immobilized cells. Results M. neoaurum R was a rough colony morphotype variant, obtained from routine plating of smooth M. neoaurum strain CICC 21097. M. neoaurum R showed rougher cell surface and aggregated in broth. The ADD production of M. neoaurum R was notably lower than that of M. neoaurum CICC 21097 during the free cell fermentation, but the yield gap could be erased after proper cell immobilization. Subsequently, repeated-batch fermentation by immobilized M. neoaurum R was performed to shorten the production cycle and enhance the bio-production efficiency of ADD. Through the optimization of the immobilization carriers and the solvents for phytosterols, the ADD productivity of M. neoaurum R immobilized by semi-expanded perlite reached 0.075 g/L/h during the repeated-batch fermentation for 40 days. Conclusions Although smooth strains that could homogenously suspended in broth seemed to be preferred in the steroid bioconversion, the rough-type strain M. neoaurum R might be able to find their place by proper cell immobilization.