Indigo production by naphthalene-degrading bacteria

A wild-type naphthalene-degrading strain Pseudomonas putida RKJ1 and two re combinant strains each of Ps. putida and Escherichia coli carrying the gene s for naphthalene degradation on a recombinant plasmid pRKJ3, produced indi go and indirubin pigments from indole. Naphthalene, salicylate and IPTG ind uced cells of naphthalene-degrading recombinant bacteria produced up to two times higher indigo compared with the uninduced cells. The maximum rates o f indigo formation by Ps. putida RKJ1, Ps. putida RKJ5/pRKJ3, Ps. putida KT 2442/pRKJ3, E. coli TB1/pRKJ3 and E. coli AB1157/pRKJ3 were 0.60, 0.80, 0.6 0, 1.20 and 1.50 nmol min(-1) mg dry biomass(-1), respectively, using indol e as the substrate. The apparent K-m values of indigo formation by these sa me bacteria were 0.22, 0.15, 0.10, 0.21 and 0.20 mmol l(-1), respectively, again using indole as the substrate. The present study revealed that E. col i AB1157 was the most efficient of the hosts tested for the expression of t he plasmid encoded genes (pRKJ3) from the wild-type strain Ps. putida RKJ1. In addition, both recombinant E. coli strains were capable of producing in digo directly from nutrient medium.