Biodegradation of AR-27 dye and electricity generation by enterobacter cloacae NF2015

Abstract

One of the major concerns of developing countries worldwide is wastewater treatment and renewable energy generation. Wastewater by-product from production activity is the cause of pollution by industries. Microbial degradation is considered a good alternative to replace wastewater treatment approaches using physical and chemical method that are less desirable due to high costs and sludge production. This study was carried out to screen and identify the potential of unidentified bacterial strains POS, F2B, PCO OIL, and B1, previously isolated from Iraqi crude oil reservoir to decolorize azo dye and implementing the system in Microbial Fuel Cell (MFC) for bioelectricity generation. The selected bacterium was identified using 16S rDNA method. The effect of co-substrates was studied to determine the minimal conditions required for maximum decolorization of AR-27 dye. Analysis of degradation were performed using UV-Vis, FTIR, CV, COD, DNS, TPP content and HPLC under facultative anaerobic and sequential facultative anaerobic-aerobic condition. Bioelectricity study was conducted using two-chambered MFC using agar salt bridge and graphite felt electrodes. The effect of different diameter of salt bridge and electrode size to electricity generation was studied. Bacteria B1 identified as Enterobacter cloacae NF2015 was found to be the most dominant decolorizing bacteria that could decolorize 99 % of 100 mg/L of AR-27 within 2 h under facultative anaerobic condition, pH 7.0, and temperature of 29 oC ± 2. Yeast extract and glucose at 0.5 g/L each was found to be the optimum co-substrates for AR-27 decolorization. The disappearance of peak in the UV–Vis spectra at 521 nm indicated the biodegradation of azo dye. The presence of oxidation and reduction peak by cyclic voltammetry analysis showed an irreversible redox reaction during the degradation. FTIR-ATR analysis confirmed that the azo linkage was cleaved after decolorization had occurred. The reduction in concentration of metabolite catechol detected by HPLC analysis confirmed a successful degradation of AR-27 dye. There was 87.6 % and 100 % COD removal after 72 hours treatment in facultative anaerobic and facultative anaerobic-aerobic condition, respectively. Optimization of the MFC voltage using 4.5 cm diameter salt bridge and 25 cm2 electrode surface area showed that the maximum OCV and CCV obtained were 809.7 ± 12 mV and 108.3 ± 19 mV, with current density and power density at 1.93 ± 0.3 mA/m2 and 0.21 ± 0.04 mW/m2. SEM and FTIR analysis revealed biofilm and extracellular polymeric substances (EPSs) functional groups development on the electrode surface during MFC operation. In conclusion, bacteria E. cloacae NF2015 from crude oil reservoir has the potential to be used in simultaneous azo dye wastewater treatment and bioelectricity generation by MFC technologies.