Cloning and expression of naphthalene dioxygenase genes from Comamonas sp. MQ for indigoids production

The naphthalene dioxygenase (NDO) genes were cloned from Comamonas sp. MQ and successfully expressed in Escherichia coli BL21 (DE3) (designated as ND_IND). The whole cells of recombinant strain ND_IND possessed relatively high transformation efficiency towards indole and most indole derivatives. According to the UV–vis and HPLC–MS analyses, the major products derived from the indoles could be indigo with different substituent groups. Furthermore, strain ND_IND was able to produce 205 mg/l indigo from 300 mg/l indole with a specific production rate of 8.4 mg/(g dry cell weight h). The effects of phenol, pyridine and quinoline on indigo production were determined, which indicated that phenol and pyridine had little inhibition on indigo production while quinoline would result in a 32% decrease in indigo yield. The present study proposed the potential application of recombinant strain ND_IND in indigoid pigments production, and offered the promise of applying strain ND_IND for the production of indigo using indole-containing wastewater as the raw materials.