Immobilization Of γ-Lactamase Producing Strain And Its Application In Synthesis Of Chiral Drug

(-)γ-lactam is the key intermediate material for the synthesis of abacavir, which serves as one powerful antiviral agent for the treatment of aids. Compared with the chemical catalysts, immobilized cells biocatalyst not only with high stereoselectivity, but also can be used repeatedly. Therefore, better application prospects are displayed on the spilt (±)γ-lactam by immobilized cells.The y-lactamase producing strain:Microbacterium hydrocarbonoxydans L29-9 has been screened, which was regarded as the experimental strain. Mechanical stability, enzymatic activity (yield of product (-)γ-lactam) and stereoselectivity (e.e. value) were taken as the index for investigation to investigate immobilized cells.Immobilization conditions of L29-9 cells were optimized as following: 6% PVA and 1% sodium alginate as composite carriers, adding 2% alcium chloride to 3% boric acid (pH 6.7) as crosslinking agent,1 mL 175 mg/mL bacterial suspension was used for a portion of immobilized cells, the prepared immobilized cells were immersed in crosslinking agent still at 4℃for hardening treatment, till then, a portion of immobilized cells was obtained.Conditions of batch biotransformation by immobilized cells were optimized as following:a portion of immobilized cells was added to 20mL 1 g/Lγ-lactam solution (pH 7.0), transformed at 30℃for 3 h on a 220 r/min shaking table.Optimal results of preservation conditions of immobilized cells during batch biotransformation interval were as following:a portion of immobilized cells was immersed in 40 mL 0.5 mM K+ solution at 4℃for preservation.By a series of optimization experiments, the biotransformation stability of immobilized cells was also studied. Under optimum conditions, the yield and e.e. value of (-)γ-lactam were 34% and>99%, respectively. The batch biotransformation was carried out for 14 cycles. The beads showed lightly decrease of yield and e.e. value in reuse up to 9 cycles.