Characterization and Kinetic study of PAH–degrading Sphingopyxis ummariensis bacteria isolated from a petrochemical wastewater treatment plant

The expansion of a microbial bank for the degradation of polycyclic aromatic hydrocarbons (PAHs) is crucial for removal of these persistent pollutants. In this study, five gram-negative, aerobic, non-fermentative bacterial strains (III-R3, IV-P11, IV-P13, IV-R13, and V-P18) were isolated from the activated sludge of a petrochemical wastewater treatment plant using enrichment pro­ tocol based on phenanthrene. The isolates were capable of utilizing phenanthrene, anthracene, and pyrene as a sole carbon and energy source in an aerobic batch aqueous system. The PAHs biodegradation yields were evaluated by gas chromatography and the bacterial isolates were identified using the 16S rRNA sequencing method. A first-order kinetic model provided the best fit to the phenanthrene degradation profiles with a correlation coefficient value of 0.95-0.98. The phenanthrene biodegradation rate constants and half-lives were measured at the range 0.653--Q.878 day-' and 0.79-1.06 day, respectively. Lower values of Anthracene degradation re­ sulted with the isolates of the current study, while a relatively high percentage of the removal of Pyrene was obtained by some of the isolates. The data obtained in this study shows that bacterial isolates have degradation preference over Mycobacterium sp. and Pseudomonas aeruginosa; and they are comparable with Pseudomonas stutzeri, Sphingomonas sp., and microbial consortium applied by other researchers. Analysis of the 16S rDNA gene sequence, when compared with the GenBank, indicates that all the strains belong to the genus Sphingopyxis with the nearest type strain being Sphingopyxis ummariensis Ul2 (MTCC 8591T). It is the first time that Sphingopyxis ummariensis is reported for its capability in the degradation of PAHs

Improving biomass and carbohydrate production of microalgae in the rotating cultivation system on natural carriers

Abstract Biofilm-based algal technologies have gained popularity due to higher biomass productivity, efficient harvesting, and water-saving over suspended growth systems. A rotating attached system was designed to assess the biofilm-forming capacity of different isolated microalgal strains from the Persian Gulf. Four microalgal strains, including two Chlorella sp., one Picochlorum sp. and one filamentous cyanobacterium Desmonostoc sp. were cultivated on four carriers: jute, cotton, yarn and nylon. The carriers’ physicochemical surface characteristics and attachment effects, like contact angle, were investigated. The incorporated biomass and exopolysaccharides (EPS) content in the suspended and biofilm system was calculated and compared. The results showed that the cyanobacterium strain had the biofilm formation capability on both jute and cotton in the attached cultivation system. Under the same culture conditions, the biomass productivity on jute and cotton carriers was significantly higher (4.76 and 3.61 g m− 2 respectively) than the growth in aqueous suspension (1.19 g m− 2 d− 1). The greatest incorporated exopolysaccharides amount was observed on jute (43.62 ± 4.47%) and the lowest amount was obtained from the growth on positive charge yarn (18.62 ± 1.88%). This study showed that in comparison with planktonic growth, the colonization of cyanobacterial cells and subsequent production of extracellular matrix and biofilm formation can lead to increased biomass production