Optimization of culture conditions to produce high yields of active Acetobactersp. CCTCC M209061 cells for anti-Prelog reduction of prochiral ketones

Abstract

BackgroundChiral alcohols are widely used in the synthesis of chiral pharmaceuticals, flavors and functional materials and appropriate whole-cell biocatalysts offer a highly enantioselective, minimally polluting route to these valuable compounds. The recently isolated strain Acetobacter sp. CCTCC M209061 showed exclusive anti-Prelog stereoselectivity for the reduction of prochiral ketones, but the low biomass has limited its commercialization and industrial applications. To tackle this problem, the effects of medium components and culture conditions on the strain's growth and reduction activity were explored.ResultsBy using a one-at-a-time method and a central composite rotatable design (CCRD), the optimal medium and culture conditions were found to be as follows: glucose 8.26 g/L, fructose 2.50 g/L, soy peptone 83.92 g/L, MnSO4·H2O 0.088 g/L, pH 5.70, 30°C and 10% (v/v) inoculum. Under the above-mentioned conditions, the biomass after 30 h cultivation reached 1.10 ± 0.03 g/L, which was 9.5-fold higher than that obtained with basic medium. Also, the reduction activity towards 4'-chloroacetophenone was markedly enhanced to 39.49 ± 0.96 μmol/min/g from 29.34 ± 0.65 μmol/min/g, with the product e.e. being above 99%. Comparable improvements were also seen with the enantioselective bioreduction of 4-(trimethylsilyl)-3-butyn-2-one to the key pharmaceutical precursor (R) - 4-(trimethylsilyl)-3-butyn-2-ol.ConclusionsThe biomass and reduction activity of Acetobacter sp. CCTCC M209061 can be greatly enhanced through the optimization strategy. This facilitates use of the strain in the anti-Prelog stereoselective reduction of prochiral ketones to enantiopure chiral alcohols as building blocks for many industries.

Response surface optimization of culture medium for enhanced docosahexaenoic acid production by a Malaysian thraustochytrid

“…The elliptical nature of the curves shown in Figure 2b (as opposed to circular shapes) indicates significant mutual interactions between the variables (yeast extract and sea salt)24. At low to moderate levels of yeast extract concentration, the lipid concentration is unaffected by increasing levels of sea salt.…”

Immobilization of Acetobacter sp. CCTCC M209061 for efficient asymmetric reduction of ketones and biocatalyst recycling

“…CCTCC M209061 were grown into late log phase under the conditions previously shown to maximise enzyme activity [7]. The immobilized biocatalysts were directly used to catalyze the asymmetric reduction of 4′-chloroacetophenone [7].…”

“…CCTCC M209061 were grown into late log phase under the conditions previously shown to maximise enzyme activity [7]. The immobilized biocatalysts were directly used to catalyze the asymmetric reduction of 4′-chloroacetophenone [7]. In the case of cells adsorbed on activated-charcoal, diatomite or polyurethane foam, or entrapped in polyvinyl alcohol (PVA), gelatin etc., biocatalysts gave low yields in ( R )-1-(4-chlorophenyl)ethanol or poor practicality (data not shown).…”

“…CCTCC M209061 was cultured in the medium containing 8.3 g/L glucose, 2.5 g/L fructose, 80 g/L soy peptone and 0.09 g/L MnSO 4 ·H 2 O, pH was adjusted to 5.7. The medium was sterilized by autoclaving at 121°C for 20 min [7]. …”

“…CCTCC M209061 can perform enantioselective biotransformations that have not been effectively performed by using other strains, several challenges remain before it can be used for industrial application. In particular, its stability and reusability were relatively poor compared to many other biocatalysts [7]. A range of immobilization technologies are commonly used for biocatalysts and can confer desirable features onto the catalyst [8].…”