Treatment of 2-naphthalene sulfonate by free and immobilized cells of indigenous isolate Comamonas sp. C2 and toxicity evaluation of biotransformed sample

Abstract

An indigenous bacterial strain Comamonas sp. C2, capable of utilizing 2-naphthalene sulfonate (2-NS) as a sole source of carbon, was isolated after enrichment of microbial diversity present in sample collected from sewage treatment plant (STP) receiving untreated or partially treated effluent from textile industries. The isolate was able to degrade 100 mg/L of 2-NS, when grown in sulfur free minimal salt medium (SFMSM), after an incubation of 8 h. The release of sulfite/sulfate ions during biotransformation, assay of protocatechuate 4, 5-dioxygenase activity and formation of metabolic intermediates like salicylaldehyde, protocatechuate and 2-hydroxy-4-carboxy-muconatesemialdehyde in the biologically treated sample indicated to the meta-cleavage of aromatic ring of 2-NS. An immobilized-cell plug flow bioreactor (PFR) was developed and evaluated for its efficiency to treat simulated feed supplemented with 100 mg/L of 2-NS. The cells of C2 were immobilized on pieces of polyurethane foam (PUF) and refractory brick pieces (RBP). The PFR, when operated at an HRT of 36 h, achieved complete degradation of 100 mg/L of 2-NS corresponding to 89% lowering of COD. The reduction in overall toxicity of 2-NS after biological treatment was evaluated using plant (Triticum aestivum and Vigna radiata) and animal (freshwater fish Channa punctatus) models, exposed to both untreated and PFR treated samples. To the best of our knowledge, there are no similar reports on exploitation of the metabolic potential of Comamonas sp. in 2-NS degradation and validation of the biological transformation by toxicity analysis.