Selection Of High Effective Decolorizing Bacteria And Research On The Mechanism Of Decolorization

In this study, the anaerobic sludge sample was collected from a biochemical printing anddying wastewater treatment plant in Jiangmen, Guangdong. The effectss of different dyes onthe structure of the anaerobic decolorizing community were studied. Then, a highly efficientdecolorizing strain was screened, and the growing and decolorizing conditions of this strainwere optimized. Based on this strain, the decolorization experiments with mixed dyes andhydrolyzed dyes were conducted.Eight kinds of dyes were used to domesticate the anaerobic decolorizing microbialcommunity enriched from the anaerobic sludge, and PCR DGGE was used to analyze Theeffectss of different dyes on the structure of anaerobic decolorizing microbial community. TheDNA fingerprint profile indicated that the structure of the enriched microbial communitychanged after it was domesticated by different dyes. The number of bacterial speciesdecreased substantially when the enriched community was domesticated by Reactive Black5and Acid Blue127. The adaptive capacity of different bacteria in the enriched bacterialcommunity was different: Lactobacillus plantarum could only adapt to Reactive Black5,while Bifidobacterium subtile couldnot adapt to any of the eight kinds of dyes. The results ofsequencing of twelve dominant bands revealed that they belonged to Lactobacillus,Enterococcus, Lactococcus and Bifidobacterium and that they can play an important role inthe process of decolorizing.A highly efficient decolorizing strain, namely strain Y8, was isolated and purified. Itcould decolorize Reactive Yellow84efficiently and its24h decolorization rate reached81.2%.According to16S rRNA gene sequencing of strain Y8and analysis of its phylogeny, strain Y8was classified into Lactobacillus sp.. The sequence had been deposited in gene bank under theaccession number of KF358705.The optimal environment for the growth of Strain Y8was: the temperature being30℃,the pH7.0in an anaerobic environment, with starch and yeast extract powder as theadditional carbon source and nitrogen source. The optimal environment for decolorization of Strain Y8was: the temperature being30℃,the pH7.0, and the inoculum quantity15%in ananaerobic still environment, with glucose and yeast extract powder as the additional carbonsource and the nitrogen source. The36h decolorization rate was above98%. Thedecolorization rate of strain Y8on azo dyes was obviously higher than that on anthraquinonedyes. The48h decolorization rate on Direct yellow4、Reactive Yellow84and Acide Red172approximated100%. However, the highest48h decolorization rate on anthraquinone dye wasabout60%, and in most cases, it was lower than30%.Reactive Yellow84was selected as the substrate dye to co degrade with eleven kinds ofdyes. Acid Red172was the only dye that could accelerate the decolorization of ReactiveYellow84and its decolorization rate reached100%in24h. The other dyes would inhibit thedecolorization of Reactive Yellow84, though The effectss varied. Acid Red35and Acid127inhibited the decolorization most, and the48h decolorization of Reactive Yellow84was only50%.The decolorizaiton experiments of hydrolyzed Reactive Black5, Reactive Yellow84andDirect Yellow4were conducted. If hydrolyzed, the decolorization rates of Direct Yellow4and Reactive Black5would be higher. Mixing the dyes with their hydrolyzed ones of thesame concentration, hydrolyzed Direct Yellow4could accelerate the decolorization of themixed dye, but had little influence on the decolorization of Direct Yellow4. HydrolyzedReactive Black5accelerated the decolorization of the mixed dye as well as Reactive Black5.Hydrolyzed Reactive Yellow84showed no influence on the decolorization of the mixed dyeand Reactive Yellow84.