Degradation of 2-methylnaphthalene by free and immobilized cells of Pseudomonas sp strain NGK1

Abstract

A Pseudomonas sp. strain NGK1 (NCIM 5120) capable of utilizing 2-niethylnaphthalene (2-MN) was immobilized in various matrices namely, polyurethane foam (PUF), alginate, agar and polyvinyl alcohol (PVA) (1.5 x 10(12) c.f.u. g(-1) beads). The degradation rates of 25 and 50 mM 2-MN by freely suspended cells (2 x 10(11) c.f.u. ml(-1)) and immobilized cells in batches, semi-continuous with shaken culture and continuous degradation in a packed-bed reactor were compared. The PUF-immobilized cells achieved higher degradation of 25 and 50 mM of 2-MN than freely suspended cells and the cells immobilized in alginate, agar or PVA. The PVA- and PUF-immobilized cells could be reused for more than 30 and 20 cycles respectively, without losing any degradation capacity. The effect of dilution rates on the rate of degradation of 25 and 50 mM 2-MN with freely suspended and immobilized cells were compared in the continuous system. Increase in dilution rate increased the degradation rate only up to 1 h(-1) in free cells with 25 mM 2-MN and no significant increase was observed with 50 mM 2-MN. With immobilized cells, the degradation rate increased with increase in dilution rate up to 1.5 h(-1) for 25 mM and 1 h(-1) for 50 mM 2-MN. These results revealed that the immobilized cell systems are more efficient than freely suspended cells for biodegradation of 2-MN.