Aspergillus Versicolor D-1& Reaction Catalyzed Selectively By Aspergillus Versicolor D-1

With high efficiency, high selectivity, security and environmental friendship, the biocatalysis possesses significant advantages over chemical catalysis in organic synthesis, especially in the asymmetric synthesis of the enantiomerically pure compounds and in the resolution of racemates. Biocatalytic reduction of the carbonyl groups or the carbon-carbon double bonds of the compounds has been utilized as a method for transforming the prochiral substrate into chiral product. This reduction is more important in organic synthesis.Among 11 Fungi tested, a new isolate Aspergillus sp. D-l was screened to transform securinine to a single product by TLC analyses. The product was prepared by the scale-up fermentation, isolated by chromatography on a silica gel column, and identified as 14,15-dihydrosecurinine by analysis of its spectra and comparison with published data. Thus, it is indicated that Aspergillus sp. D-l catalyzes the reduction of the γ,δ-double bond of the unsaturated lactone in securinine.Aspergillus sp. D-l was identified by morphological and molecular biological means. Based on macromorphological and micromorphological characters, as well as conidium ornamentation observed with scanning electron microscopy (SEM), Aspergillus sp. D-l was affiliated to Aspergillus Section Versicolores. Further, DNA sequence of the internal transcribed spacer (ITS) was used as the molecular characteristic, and analyzed with the DNAMAN 5.2.2 program and the Mega 3.0 program. In similarity research and phylogenetic analysis of the ITS region, Aspergillus sp. D-l is more closely relately to Aspergillus versicolor and assigned to the species A. versicolor. The strain was named A. versicolor D-1. This is the first reported that the species A. versicolor has the ability to reduce the conjugated γ,δ-double bond of the unsaturated lactone.A-factor experiments were carried out to evaluate the effects of initial pH, temperature and substrate concentrations on the reduction of securinine by resting culture of A. versicolor D-1. it is shown that the maximal reduction activity of the resting culture was 486.7 mg/L/g (dry cell) after incubation of 8 h in 0.06 mol/L phosphate buffer (pH 7.0) containing securinine (146.7 mg/L) at 250 r/min and 28 ℃, and A. versicolor D-l reduced securinine in over 98% yield. At the same time, the maximum concentration of 14,15-dihydrosecurinine remained constant in the culture broth during the following 16 h incubation. Thus, it was suggested that Aspergillus versicolor D-l selectively reducted securinine. The fact that the...