Pollution Research Paper

DECOLORIZATION AND DETOXIFICATION OF METHYLENE BLUE BY A LEBANESE BACTERIAL STRAIN; BACILLUS LICHENIFORMIS HE

HODAYUSEF, SALWA ABDEL RAHMAN, ENAS DABBOUS AND HASSAN HAMMUD

Abstract

Dyes are not easily biodegradable, their release into the environment represent a serious pollution problem. A bacterial strain isolated from the effluents of a tannery located in Bekaa province- Lebanon and identified as B. licheniformis HE by 16S rDNA sequencing, was found to be highly effective to decolorize methylene blue (MB). The dye was efficiently decolorized in static compared to shaken cultures. The bacterium exhibited remarkable color removal ability over a wide range of MB concentrations (5-100 mg/L) and pH (5-9). 92.1% decolorization of MB (25 mg/L) was attained after 24 hours in 40 mL medium/flask (pH 7) (10% inoculum size) at 37 °C in static condition. The decolorization process was optimized using Plackett-Burman design. Seven fermentation factors were screened; the most significant variables affecting MB decolorization and having the highest confidence percentage were NaCl and inoculum size. Under a near optimal condition, the MB decolorization percent increased to 99.8%. Omitting carbon and nitrogen sources from the medium inhibited the decolorization performance. Spectrophotometric measurements (350-700 nm) of methylene blue before and after treatment with B. licheniformis HE, indicated the change in the structure of MB. A phytotoxicity study revealed that the biodegradation of MB resulted in its detoxification; Triticum aestivum and Cicer arietinum irrigated with the treated dye were able to germinate and grow, which indicated a possible use of dye containing effluents in the irrigation of plants after bioremediation process.