Characterization and application of D-amino acid oxidase and catalase within permeabilized Pichia pastoris cells in bioconversions.

The high-density fermentation of recombinant Pichia pastoris was carried out in a 1-L fermentor. After 60 h of fermentation, the activities of D-amino acid oxidase (DAAO) and catalase assayed with the permeabilized cells attained 12,532 and 684,800 U/L, respectively. Additionally, the stability of DAAO and catalase within the permeabilized cells was relatively high. The half-life of the two enzymes reached 14.5 and 4.0 d at 30 degrees C, respectively. Furthermore, these permeabilized cells could convert D-phenylalanine into 99% phenylpyruvate within 100 min and could be efficiently reused up to 13 cycles. After being treated with base and heating, these treated permeabilized cells could be reused up to three cycles in a batchwise conversion of cephalosporin C, and about 90% 7-beta-(4-carboxybutanamido)-cephalosporanic acid was ultimately obtained at each cycle.