Degradation of Salicylic Acid by Free and Immobilized Cells of Pseudomonas sp. Strain NGK1.

A Pseudomonas sp. strain NGK1 (NCIM 5120)
capable of utilizing salicylate was immobilized in alginate
and polyurethane foam (PUF). The degradation rate of salicylate
by freely suspended cells was compared with the degradation
rate by immobilized cells. In an initial 20 and 40 mM salicylate,
free cells (2×1011 cfu ml-1
) degraded to 16 and 14 mM, alginateentrapped cells degraded to 18 and 26 mM, and PUF-entrapped
cells degraded to 20 and 32 mM salicylate, respectively, in
batch cultures. The alginate- and PUF-entrapped cells were
used in repeated batch and continuous culture systems. The
efficiency of both the immobilized systems for the degradation
of salicylate was compared. It has been observed that the
PUF-entrapped cells could be reused for more than 20 cycles
whereas alginate-entrapped cells could be reused for a maximum
of only 12 cycles, after which a decrease in degradation rate
was observed with the initial 20 and 40 mM salicylate. The
continuous degradation of salicylate by freely suspended
cells showed a negligible degradation rate of salicylate when
compared with immobilized cells. With the immobilized cells
in both alginate and polyurethane foam, the degradation rate
increased with an increase in the dilution rate up to 2 h-1
for
20 mM, and 1.5 h-1
for 40 mM salicylate. The results revealed
that PUF-entrapped cells were more efficient for the degradation
of salicylate than alginate-entrapped cells and freely suspended
cells