A Concise Synthesis of 25-Hydroxycholesterol from Hyodesoxycholic Acid

Bioconversion of vitamin D3 into calcitriol by Actinomyces hyovaginalis isolate CCASU- A11-2

Vitamin D₃ is a fat-soluble prohormone that is activated inside the liver to produce 25-hydroxyvitamin D₃ (calcidiol), and in the kidney to produce the fully active 1α, 25-dihydroxy vitamin D₃ (calcitriol). A previous work piloted in our laboratory, resulted in a successful recovery of a local soil-promising Actinomyces hyovaginalis isolate CCASU-A11-2 capable of converting vitamin D₃ into calcitriol. Despite the rising amount of research on vitamin D₃ bioconversion into calcitriol, further deliberate studies on this topic can significantly contribute to the improvement of such a bioconversion process. Therefore, this work aimed to improve the bioconversion process, using the study isolate, in a 14 L laboratory fermenter (4 L fermentation medium composed of fructose (15 g/L), defatted soybean (15 g/L), NaCl (5 g/L), CaCO₃ 2 g/L); K₂HPO₄, (1 g/L) NaF (0.5 g/L) and initial of pH 7.8) where different experiments were undertaken to investigate the effect of different culture conditions on the bioconversion process. Using the 14 L laboratory fermenter, the calcitriol production was increased by about 2.5-fold (32.8 µg/100 mL) to that obtained in the shake flask (12.4 µg/100 mL). The optimal bioconversion conditions were inoculum size of 2% v/v, agitation rate of 200 rpm, aeration rate of 1 vvm, initial pH of 7.8 (uncontrolled); addition of vitamin D₃ (substrate) 48 h after the start of the main culture. In conclusion, the bioconversion of vitamin D₃ into calcitriol in a laboratory fermenter showed a 2.5-fold increase as compared to the shake flask level where, the important factors influencing the bioconversion process were the aeration rate, inoculum size, the timing of substrate addition, and the fixed pH of the fermentation medium. So, those factors should be critically considered for the scaling-up of the biotransformation process.

Efficient biotransformation of vitamin D3 to 25-hydroxyvitamin D3 by a newly isolated Bacillus cereus strain

25-hydroxyvitamin D₃ has attracted considerable attention due to its great medical value and huge market demand in animal husbandry. Microbial production of 25-hydroxyvitamin D₃ has been recognized as an alternative superior to traditional chemical synthesis. In this study, a Gram-positive bacteria zju 4-2 (CCTCC M 2019385) was isolated from the soil using vitamin D₃ as the sole carbon source and was identified as Bacillus cereus according to its physiological characteristics and 16S rRNA analysis, which also showed a relatively high capacity for 25-hydroxyvitamin D₃ production. Through systematic optimization of different catalytic conditions, the optimal solvent system of vitamin D₃, vitamin D₃ addition time and concentration, temperature, and pH were shown to be propylene glycol/ethanol (v/v = 9:1), early stationary phase, 2 g/L, 37 °C, and pH 7.2, respectively. With these optimal conditions, 796 mg/L of 25-hydroxyvitamin D₃ was achieved after 48 h bioconversion with zju 4-2 at the shake flask level. Finally, up to 830 mg/L 25-hydroxyvitamin D₃ with a yield of 41.5% was obtained in a 5 L fermentation tank. Our developed biotransformation process with this newly isolated strain provides a platform to produce 25-hydroxyvitamin D₃ efficiently at industrialization scale.