Effect of chlorination on beta-D-galactosidase activity of sewage bacteriaand Escherichia coli

摘要

The effect of chlorine on beta-D-galactosidase activity of sewage bacteria and Escherichia coli was studied. beta-D-galactosidase activity of sewage was more resistant to chlorine than faecal coliform cultivability. At low initial dosage (0.05 mg Cl-2 l(-1)) neither cultivability (colony-forming units (cfu)), nor enzyme activity of E. coli suspensions were severely impaired. When initial chlorine concentration was increased to 0.1 mg Cl-2 l(-1), the cfu number decreased whereas enzyme activity remained high, i.e. the enzyme activity calculated cfu(-1) increased. At higher chlorine doses both cfu and enzyme activity were reduced, but non-cultivable cells retained assayable activity after chlorination. Mean values of the enzyme activity calculated cfu(-1) decreased when the chlorine dosage was increased from 0.1 to 0.5 mg Cl-2 l(-1), but were not significantly different (P > 0.05) for dosages of 0.2-0.7 mg Cl-2 l(-1). After chlorination, beta-D-galactosidase activity of E. coli was less reduced than cfu and direct viable count numbers, but more reduced than 5-cyano-2-3, ditolyl tetrazolium chloride and total cell counts, and the enzyme activity represented an alternative activity parameter of chlorinated samples.