title: Using orthogonal design to determine optimal conditions for biodegradation of phenanthrene in mangrove sediment slurry.
abstract: In the present paper, the effects of four factors, each at three levels, on biodegradation of phenanthrene, a 3-ring PAH, in contaminated mangrove sediment slurry were investigated using the orthogonal experimental design. The factors and levels were (i) sediment types (clay loam, clayey and sandy); (ii) different inoculums (Sphingomonas sp., a mixture of Sphingomonas sp. and Mycobacterium sp., and without inoculum); (iii) presence of other PAHs (fluorene, pyrene, and none); and (iv) different salinities (5, 15 and 25 ppt). Variance analysis based on the percentages of Phe biodegradation showed that the presence of other PAHs had little effect on phenanthrene biodegradation. The kinetics of phenanthrene biodegradation in all experiments was best fitted by the first order rate model. The highest first order rate constant, k value was 0.1172 h(-1) with 97% Phe degradation; while the lowest k value was 0.0004 and phenanthrene was not degraded throughout the 7-d experiment. The p values of k for the four factors followed the same trend as that for the biodegradation percentage. Difference analysis revealed that optimal phenanthrene biodegradation would take place in clay loam sediment slurry at low salinity (5 to 15 ppt) with the inoculation of both Sphingomonas sp. and Mycobacterium sp.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
authors.forename: Jian Lin
authors.initials: JL
authors.lastname: Chen
authors.forename: Kwai Chi
authors.initials: KC
authors.lastname: Au
authors.forename: Yuk Shan
authors.initials: YS
authors.lastname: Wong
authors.forename: Nora Fung Yee
authors.initials: NF
authors.lastname: Tam
mesh_terms: D001673:Biodegradation, Environmental; D007700:Kinetics; D009161:Mycobacterium / Q000378:metabolism; D010616:Phenanthrenes / Q000378:metabolism*; D043982:Rhizophoraceae / Q000737:chemistry; D020578:Sphingomonas / Q000378:metabolism
chemical_list: D010616:Phenanthrenes; C031181:phenanthrene