Degradation of acrylamide by immobilized cells of a Pseudomonas sp. and Xanthomonas maltophilia

Two bacterial isolates capable of utilizing acrylamide as the sole source of carbon and nitrogen were isolated from herbicide-contaminated soil samples and identified as Pseudomonas sp. and Xanthomonas maltophilia. Batch cultures of Pseudomonas sp. and X. maltophilia completely degraded 62.8 mM acrylamide to acrylic acid and ammonia in 24 and 48 h, respectively. Pseudomonas sp. And X. maltophilia, when immobilized in calcium alginate, markedly increased the rate of degradation of acrylamide over batch cultures. Cells of the isolates immobilized in calcium alginate degraded acrylamide to acrylic acid and ammonia in less than 6 h. Initial metabolism of acrylamide by immobilized cells of Pseudomonas sp. followed by inoculation with nonimmobilized cells after 6 h totally removed acrylamide and its metabolites in 72 h. A similar procedure with X. maltophilia resulted in the total metabolism of acrylamide in 96 h. An inducible, intracellular amidase was responsible for the hydrolysis of acrylamide to acrylic acid and ammonia. The specific activity of Pseudomonas sp. amidase was higher than the specific activity of X. maltophilia amidase.Key words: acrylamide, biodegradation, immobilization.