BACTERIAL METABOLISM OF CHLORINATED DEHYDROABIETIC ACIDS OCCURRING INPULP AND PAPER-MILL EFFLUENTS

Chlorinated dehydroabietic acids are formed during the chlorine bleach ing of wood pulp and are very toxic to fish. Thus, destruction of thes e compounds is an important function of biological treatment Systems f or pulp and paper mill effluents. In this study, 12 strains of diverse , aerobic resin acid-degrading bacteria mere screened for the ability to grow on chlorinated dehydroabietic acids as sole organic substrates . ALI seven strains of the class Proteobacteria able to use dehydroabi etic acid were also able to use a mixture of 12- and 14-chlorodehydroa bietic acid (Cl-DhA). None of the strains used 12,14-dichlorodehydroab ietic acid, Sphingomonas sp. strain DhA-33 grew best on Cl-DhA and sim ultaneously removed both Cl-DhA isomers. Ralstonia sp. strain BKME-6 w as typical of most of the strains tested, growing more slowly on Cl-Dh A and leaving higher residual concentrations of Cl-DhA than DhA-33 did . Strains DhA-33 and BKME-6 mineralized (converted to CO2 plus biomass ) 32 and 43%, respectively, of carbon in Cl-DhA consumed. Strain DhA-3 3 produced a metabolite from Cl-DhA, tentatively identified as 3-oxo-1 4-chlorodehydroabietin, and both strains produced dissolved organic ca rbon which may include unidentified metabolites. Cl-DhA removal mas in ducible in both DhA-33 and BKME-6, and induced DhA-33 cells also remov ed 12,14-dichlorodehydroabietic acid, Based on activities of strains D hA-33 and BKME-6, chlorinated DhAs, and potentially toxic metabolite(s ) of these compounds, are relatively persistent in biological treatmen t systems and in the environment.