Screening, Identification And Degradation Characteristics Of A Salt Tolerant Phenol-Degrading Bacterium

A strain that could utilize phenol as sole carbon source was screened frompetroleum-contaminated soil and identified through physiological biochemistry test and16S rDNA sequencing, named as JDD1H.The growth characteristics of JDD1H under thesalinity surroundings was investigated and the technologcial conditions wasoptimized.Influences of addtional carbon source, nitrogen source and surfactant wasresearched, together with the degrading broad spectrum and growth kinetics pattern wasstudied.Plus, partial henol hydroxylase gene was cloned The results showed that the strainwas identified as Rhodococcus sp., with salt tolerance of5%, the suitable temperaturerange for growth was30⁴0℃, pH6⁸. Heavy metals Ag⁺, Fe³⁺, Ni²⁺, Co²⁺, Cu²⁺causedsuppression to JDD1H growth in the order of Ag⁺, Fe³⁺, Ni²⁺, Co²⁺, Cu²⁺.Results of degradation technological optimization exhibited that the proper conditonsfor degradation was salt concentration0⁵%, pH6⁸,30⁴0℃with cultivation dose of5%.Phenol concentration under300mg/L could be completely degraded within24⁷2h,decreasing when initial concentration up to400mg/L, hardly degraded when above500mg/L. Additional carbon source of lactose, cane sugar, glucose, mannitol, starch promotedpheol degradation within50²000mg/L obviously. While sodium acetate promoteddegradation process with concentration under2000mg/L,and inhibited above2000mg/L.Additional nitrogen sources of peptone yeast extract and urea accelerated the degradationgreatly. When concentration of peptone yeast and extract was increased to500mg/L, ureato1000mg/L, the promotion was turn out to be steady. Inorganic nitrogen source of NH4Cland （NH4）2SO4had promotion to some extent, however much weaker than organic nitrogensource50¹000mg/L TW-80suppressed phenol degradation, getting weaker with theincrease of concentration and promoted with1500²000mg/L. CTAB of20⁵00mg/Linhibited phenol degradation even without being degraded basically.Degrading broad spectrum of the strain presented that JDD1H had some degradingpotential of2-nitrophenol,2-chlorophenol, salicylic acid with degrading efficiency of21.3%,49.55%,38.1%respectively.Growth kinetics revealed that the specific growth rateincreased with the phenol concentration increasing within phenl concentration under200mg/L, while decreased with concentraion rising in the range of200⁶00mg/L. Haldanemode could be used to describe the growth pattern well with kinetic parameter of μmax, Ks, Ki being0.16h-1,322.33mg/L,67.65mg/L, respectively.Phenol hydroxylase conserved sequence was treated as primers and the aquired brandwas coloned in this study, verifying the existence of phenol hydroxylase gene.Thephylogenetic tree based on the partial amino acid sequences of phenol hydroxylase gene ofstrain JDD1H suggested that the closely phylogenetic relationship exist at the amino acidlevel with Pseudomona sp., Arthrobacter sp. It might be speculated that phenolhydroxylase gene in different bacteria came from the same ancestor still changed duringlong-term evolution according to the difference in phenol hydroxylase gene.