Isolation and screening of D-amino acid amidase producing bacteria from soil samples

Abstract

Isolation and screening of D-amino acid amidase producing bacteria from fifty-four soil samples taken on Hat Yai campus of Prince of Songkla University were conducted using acclimation culture technique in medium broth containing D-phenylalanine amide as a sole source of nitrogen. Bacteria capable of growing at 30ºC and 45ºC were screened and isolated. Twenty-one and seventeen soil samples showed the hydrolysis of D-phenylalanine amide to D-phenylalanine determined by thin layer chromatography and forty-seven and thirty-four strains were isolated at 30ºC and 45ºC, respectively. Each isolate obtained was screened for its ability to degrade D-phenylalanine amide. Thirteen of forty-seven strains and nineteen of thirty-four strains isolated at 30ºC and 45ºC, respectively exhibited D-phenylalanine amide degradation. However, only isolate BS16 exhibited degradation toward D-tert-leucine.The enzyme activity toward D-phenylalanine amide was detected from the bacterial cells, but not in supernatant indicating that the amidase was an intracellular enzyme. The bacterial cells grown in the broth with and without D-amino acid amide showed enzyme activity leading to the conclusion that it was constitutive enzyme