Strains Screening With Carbonyl Reductase And Isolation And Characterization Of A Strain With Both Carbonyl Reductase And Hydroxylase Activities

Carbonyl-reducing reaction plays a critical role in biosynthesis of chiral alcohols and biological metabolism of many endogenous and xenobiotic. At present, the stereomerically pure compounds are widely employed as useful building blocks in many fields, asymmetric reduction of prochiral ketones is the most straightforward approach to preparing chiral alcohols that are frequently required as intermediates for synthesizing pharmaceuticals and agricultural chemical compounds. Recently, many micro-organisms and isolated enzymes have been applied in asymmetric bioreduction.Hydroxylase is indispensable in steroids and aromatic compound biotransformation.Because of the prospect of its extensive application, hydroxylase has already become the hot topic in this field. Aromatic compounds that are oxygenated or hydroxylated are of great value for organic synthesis. The hydroxylation reaction is also a significant step for microbial degradation of pollutants that generally contain aromatics.In this study is to find a rapid method of screening and to isolate micro-organisms that can reduce different aldehydes and ketones substrates. By using enrichment culture method more than900strains were isolated. among them, a Rhodococcus sp strain with hydroxylase and carbonyl reductase activity and four Streptomyces sp strains were studied in details.Most noteworthy, the isolated Rhodococcus sp.1-0130can catalyze two different reactions under aerobic and anaerobic conditions for para-acetylphenol to give1-(3,4-dihydroxyphenyl)ethanone and S-(-)-1-(para-hydroxyphenyl)ethanol, respectively16S rDNA study and construction of phylogenetic tree showed that it was phylogenetically affiliated with species of the genus Rhodococcus and had highest identity(99%) with Rhodococcus pyridinivorans, so it was named as Rhodococcus sp1-0130. Under optimal conditions for reduction (fungus age17h, pH7.0,37℃, Glu2g/L, anaerobic conditions) S-(-)-1-(para-hydroxyphenyl)ethanol was obtained with95%enantiomeric excess (e.e.) and85.2%conversion. For hydroxylation,1-(3,4-dihydroxyphenyl)ethanone was obtained with>99%conversion and92.7yield under the optimal conditions (fungus age17-22h, pH8.0,35℃, Glu3g/L, aerobic conditions). The substrate profiles for reduction and hydroxylation were also investigated.