Medium optimization for enhanced production of carbonyl reductase by Candida tropicalis 104 by response surface methodology / 生物工程学报

Using response surface method, we optimized the medium for the asymmetric whole cell biotransformation by Candida tropicalis 104. This strain was used for microbial reduction of 1-[3,5-bis(trifluoromethyl)phenyl] ethanone to (S)-l-[3,5-bis(trifluoromethyl)phenyl] alcohol, with enantiomeric excess(e.e.) reached more than 99.9%. Fractional factorial design was used to evaluate the effects of medium components on carbonyl reductase activity of Candida tropicalis 104. Yeast extract, glucose and NH4Cl were the most important factors among six tested variables that influence the enzyme activity for the biotransformation process. Based on the experimental results, the path of steepest ascent was undertaken to approach the optimal region of these factors. Central composite design and response surface analysis were subsequently employed for further optimization. The optimal medium for Candida tropicalis 104 was composed of (in g/L): glucose 47.14, yeast extract 13.25, NH4Cl 2.71, MgSO4.7H2O 0.4, KH2PO4 1, K2HPO4 1. Under the optimum conditions, the maximum enzyme activity of 852.75 U/L in theory and 851.13 U/L in the experiment were obtained, with an increase of 65.2% compared to the original medium components.

Biodehydrogenation of 11beta-hydroxyl melroxyprogesterone by Arthrobacter simplex UR016 in microemulsion system / 生物工程学报

To improve mass transfer and enhance the yield for C(1,2) biodehydrogenation of steroid 11beta-hydroxyl medroxyprogesterone, we carried out the dehydrogenation reaction of 11beta-hydroxyl medroxyprogesterone in an oil-in-water (O/W) microemulsion by Arthrobacter simplex UR016. We studied the effects of system composition, dehydrogenation temperature and substrate concentration on microbial transformation. We formulated a suitable O/W microemulsion system with Arthrobacter simplex UR016 culture broth as aqueous phase, 10 g/L of edible oil as oil phase, 4 g/L of Tween-O80 and 7% (V/V) alcohol as surfactant and cosurfactant. The optimal dehydrogenation temperature was 33 degrees C. The results showed that in Tween-80/alcohol/edible oil/water microemulsion system, the hydrophobic steroid was solubilised and diffused effectively, with the maximum conversion rate of 88.6% at 46 h under 4 g/L substrate concentration, an increase of 66.2% compared to that in aqueous system. The C(1,2) biodehydrogenation of 11beta-hydroxyl medroxyprogesterone is more efficient in water-edible oil microemulsion system than in aqueous system.