INFLUENCE OF ORGANIC AND INORGANIC GROWTH SUPPLEMENTS ON THE AEROBIC BIODEGRADATION OF CHLOROBENZOIC ACIDS

The effect of yeast extract and its less complex substituents on the r ate of aerobic dechlorination of 2-chlorobenzoic acid (2-ClBzOH) and 2 ,5-dichlorobenzoic acid (2,5-Cl(2)BzOH) by Pseudomonas sp. CPE2 strain , and of 3-chlorobenzoic acid (3-ClBzOH), 4-chlorobenzoic acid (4-ClBz OH) and 3,4-dichlorobenzoic acid (3,4-Cl(2)BzOH) by Alcaligenes sp. CP E3 strain were investigated. Yeast extract at 50 mg/l increased the av erage dechlorination rate of 200 mg/l of 4-ClBzOH, 2,5-Cl(2)BzOH, 3,4- Cl(2)BzOH, 3-ClBzOH and 2-ClBzOH by about 75%, 70%, 55%, 7%, and 1%, r espectively. However, in the presence of yeast extract the specific de chlorination activity of CPE2 and CPE3 cells (per unit biomass) was al ways lower than without yeast extract, although it increased significa ntly during the exponential growth phase. When a mixed vitamin solutio n or a mixed trace element solution was used instead of yeast extract the rate of 4-ClBzOH dechlorination increased by 30%-35%, whereas the rate of 2,5-Cl(2)BzOH and 3,4-Cl(2)BzOH dechlorination increased by on ly 2%-10%. The presence of vitamins or trace elements also resulted in a specific dechlorination activity that was generally higher than tha t observed for the same cells grown solely on chlorobenzoic acid. The results of this work indicate that yeast extract, a complex mixture of readily oxidizable carbon sources, vitamins, and trace elements, enha nces the growth and the dechlorination activity of CPE2 and CPE3 cells , thus resulting in an overall increase in the rate of chlorobenzoic a cid utilization and dechlorination.