Isolation of Pesticides Degrading Bacterial Consortium and its Application for Industrial Wastewater Treatment

Abstract

Wastewater from agrochemical industries is disposed off without any treatment into nearby water bodies; hence there is a dire need to improve remediation approaches for its removal from environment. It is hypothesized that bacterial strains present in wastewater, after acclimatization, could use Chlorpyrifos (CP) as a sole source of carbon and energy and convert it into less toxic substances, both in free as well as immobilized form. Current study aimed at isolation of bacterial consortium capable of efficient CP biodegradation in mineral salt media (MSM), simulated pesticide wastewater (SWW) and real industrial wastewater (WW) in free and immobilized form. In order to produce environmentally stable immobilization matrix for bacterial consortium, potential of calcium alginate matrix coupled with polysulfone was investigated. Biodegradation potential of bacterial consortium isolated from wastewater and agricultural soil, for CP in MSM, SWW and WW was investigated. Bacterial consortium was immobilized in Calcium Alginate Microspheres (CAMs) and coated with polysulfone to produce environmentally stable macrocapsules (MCs). Bacterial strains were identified using 16S rRNA nucleotide sequence analysis as Pseudomonas kilonensis SRK1 (KT013088), Serratia marcescens SRK2 (KT013089), Bacillus pumilus SRK4 (KT013091), Achromobacter xylosoxidans SRK5 (KT013092) and Klebsiella sp. T13 (KT013093). About 98% CP removal was observed at initial CP concentration of 400 mg/L in 48 h in MSM when free cells were used as consortium. In WW bacterial consortium achieved ~29% removal efficiency of initial CP concentration (545 mg/L). After pH adjustment and addition of glucose in WW >97% CP removal efficiency was achieved in WW. MCs have high thermal, pH and chemical stability than CAMs. Complete biodegradation of CP (100-600 mg/L) was achieved using MCs within 18 h much less than free cells. CAMs and MCs retain >96% residual activity in MSM upto 5 and 13 cycles respectively. In WW >90 residual activity was maintained upto 11batches by MCs. MCs have shown unaltered biomass retention and residual activity (95%) over 16 weeks of storage. GCMS analysis has shown 3, 5, 6-trichloro-2-pyridinol (TCP), 3, 5, 6-trichloro-2methoxypyridine (TMP) and diethyl-thiophosphate (DETP) as metabolites. MCs have shown considerable benefits over free cells i.e. tolerance for higher CP concentration, complete removal in short duration, reusability, stability, protecting bacterial cells against nontargeted compounds present in wastewater. Study advances potential for field application of immobilized bacteria for biotreatment of pesticide contaminated wastewater.