The isolation and characterisation of a salicylate-hydroxylase-producing strain of Pseudomonas putida

A salicylate-hydroxylase-producing strain of Pseudomonas putida with an unusual capability to grow at toxic levels of salicylate up to 10 g l^-1 has been isolated. It grew well under continuous culture conditions, with optimum growth at pH 6.5 and a temperature of 25° C. The use of an ammonium salt as a nitrogen source, instead of nitrate, resulted in a 30-40% increase in its biomass yield coefficient. Optimum growth under continuous culture conditions was achieved using 4 g l^-1 salicylate at 25° C, pH 6.5 and 0.2 h^-1 dilution rate. High salicylate hydroxylase enzyme activity [236 units (U) l^-1] and productivity (424.8 U h^-1) were obtained at a dilution rate of 0.45 h^-1 using a mineral medium containing 4 g l^-1 of salicylate. Operating under continuous culture conditions with oxygen limitation and a slight accumulation of residual salicylate (0.2 g l^-1) resulted in a decrease in culture performance and enzyme productivity.