Objective: Permeability of hydrophobic steroid substrates across cell membrane is a critical factor during microbial bioconversion. To increase substrate intake, the feasibility of some organic solvents and emulsifiers as substrate carrier on the bioconversion of 6-methylene androstenedione to exemestane was assessed.Methods: Androstenedione, a commonly available steroid precursor, was chemically converted 6-methylene androstenedione. The time course of exemestane accumulation was estimated after addition of 6-methylene androstenedione dissolved in some organic solvents or dispersed with emulsifiers by growing and immobilized cells of Arthrobacter simplex NCIM 2449 in shake flask cultures. Results: The use of substrate carriers for addition of 6-methylene androstenedione enhanced the bioconversion several folds. With growing bacterium in triplicate flasks, a peak mol % bioconversion recorded was- ethanol (67.25, 72 h); soybean oil + tween 80 (50.37, 48 h); acetone (38.84, 48 h); soybean oil (38.36, 48 h); lecithin (32.73, 48 h), methanol (32.71, 48 h) and tween 80 (10.37, 48 h). As compared to the growing cells, the bioconversion with Ca-alginate immobilized cells was delayed and peak mol % bioconversion was recorded as ethanol (60.78, 120 h); soybean oil + tween 80 (42.98, 120 h); methanol (40.50, 72 h); soybean oil (38.36, 48 h); acetone (31.18, 72h ) and lecithin (33.67, 120 h); tween 80 (13.87, 120 h).Conclusion: The use of substrate carriers for addition of 6-methylene androstenedione increased the permeability of substrate and may be used to increase the yield of exemestane and reduce incubation time.
SUBSTRATE CARRIERS FOR C-1(2)-DEHYDROGENATION OF 6-METHYLENE ANDROSTENEDIONE TO EXEMESTANE BY GROWING AND IMMOBILIZED ARTHROBACTER SIMPLEX NCIM 2449