D-amino acid oxidase from Trigonopsis variabilis: Immobilization of whole cells in natural polymeric gels for glutaryl-7-aminocephalosporanic acid production

The enzymatic oxidation of cephalosporin C to glutaryl-7- aminocephalosporanic acid (glutaryl-7-ACA) was carried out utilizing permeabilized whole cells of the yeast Trigonopsis variabilis entrapped in Ca-alginate beads. The biomass, cultured in a rich medium containing DL- methionine and harvested after 72 h of growth, exhibited high levels of D- amino acid oxidase activity. Prior to use, the whole cells were permeabilized with four freeze-thawing cycles and immobilized in polysaccharide matrices, such as Ca-alginate and ?-carrageenan, and in an insolubilized gelatin gel. The best results in terms of activity yield and storage stability were obtained with cells entrapped in Ca-alginate beads. These cells were utilized for glutaryl-7-ACA production in a continuous stirred batch reactor (CSTR) and in a packed bed reactor working as a plug flow reactor (PFR), using 50 mM cephalosporin C as substrate. The performances of the two systems were compared. The overall productivities (calculated on a void volume basis) were 1.64 g and 255 mg of glutaryl-7-ACA l -1 h -1 in the PFR and in the CSTR, respectively.