Immobilization of Rhodococcus AJ270 and Use of Entrapped Biocatalyst for the Production of Acylic Acid

摘要

Rhodococcus AJ270 is adsobed by Dowex 1 at 15.4 mg dry weight per g resin with maximum amidase specific acitvity observed at lower loadings. Bacteria form a monolayer on the resin surface, and adsorption is complete within 2 min. AJ270 can be entrapped in agar and agarose gels (optimum loading:20 mg dry weight bacteria per cm~3 gel). Adsorption and entrapment improve amidase thermal stability 3-4 fold, and entrapment shifts the pH optimum from 8 to 7. Adsobed and free bacteria show similar values for K_m and V_(max), but entrapped bacteria have higher K_m values. Compared with bacteria adsorbed to Dowex, the activity per cm~3 of matrix of agar-entrapped AJ270 is eight-fold higher. In stirred-tank reactors, exposure to acrylic acid reduces the amidase activity of the biocatalyst in the hydrolysis of acrylamide. In column reactors, entrapped AJ270 suffers little reduction in amidase activity against 0.25 M acrylamide over 22h continuous operation.