Simultaneous heterotrophic nitrification and aerobic denitrification at high initial phenol concentration by isolated bacterium Diaphorobacter sp. PD-7

A strain capable of phenol degradation, hetemtrophic nitrification and aerobic denitrification was isolated from activated sludge of coking-plant wastewater ponds under aerobic condition. Based on its morphology, physiology, biochemical analysis and phylogenetic characteristics, the isolate was identified as Diaphorobacter sp. PD-7. Biodegradation tests of phenol showed that the maximum phenol degradation occurred at the late phase of exponential growth stages, with 1400 mg·L^-1 phenol completely degraded within 85 h. Diaphorobacter sp. PD-7 accumulated a vast quantity of phenol hydroxylase in this physiological phase, ensuring that the cells quickly utilize phenol as a sole carbon and energy source. The kinetic behavior ofDiaphorobacter sp. PD-7 in batch cultures was investigated over a wide range of initial phenol concentrations （0-1400mg·L^-1） by using the Haldane model, which adequately describes the dynamic behavior of phenol biodegradation by strain Diaphombacter sp. PD-7. At initial phenol concentration of 1400mg· L^-l, batch experiments （0.25 L flask） of nitrogen removal under aerobic condition gave almost entirely removal of 120.69mg· L^- 1 ammonium nitrogen within 75 h, while nitrate nitrogen removal reached 91% within 65 h. Moreover, hydroxylamine oxidase, periplasmic nitrate reductase and nitrite reductase were successfully expressed in the isolate.

Coupled biodegradation of p-nitrophenol and p-aminophenol in bioelectrochemical system:Mechanism and microbial functional diversity

Biodegradation mechanisms and microbial functional diversity during coupled pnitrophenol(PNP)and p-aminophenol(PAP)degradation were studied in a bioelectrochemical system.PNP in the biocathode and PAP in the bioanode were almost completely removed within 28 hr and 68 hr respectively.The degradation followed the steps including hydrating hydroxyalkylation,dehydrogenating carbonylation,and hydrolating ring cleavage,etc.Metagemomic analysis based on the KEGG and egg NOG database annotations revealed the microbial composition and functional genes/enzymes related to phenol degradation in the system.The predominant bacteria genera were Lautropia,Pandoraea,Thiobacillus,Ignavibacterium,Truepera and Hyphomicrobium.The recognized biodegradation genes/enzymes related to pollutant degradation were as follows:pmo,hbd,&ppo for phenol degradation,nzba,amie,&badh for aromatic degradation,and CYP&p450 for xenobiotics degradation,etc.The co-occurrence of ARGs(antibiotic resistant genes),such as ade F,Mex J,Erm F,PDC-93 and Escherichiacolimdf A,etc.,were annotated in CARD database during the biodegradation process.The Proteobacteria&Actinobacteria phylum was the primary host of both the biodegradation genes&ARGs in this system.The microbial functional diversity ensured the effective biodegradation of the phenol pollutants in the bioelectrochemical system.

Molecular level biodegradation of phenol and its derivatives through dmp operon of Pseudomonas putida:A bio-molecular modeling and docking analysis

Participation of Pseudomonas putida-derived methyl phenol（dmp） operon and Dmp R protein in the biodegradation of phenol or other harmful, organic, toxic pollutants was investigated at a molecular level. Documentation documents that P. putida has Dmp R protein which positively regulates dmp operon in the presence of inducers; like phenols. From the operon,phenol hydroxylase encoded by dmp N gene, participates in degrading phenols after dmp operon is expressed. For the purpose, the 3-D models of the four domains from Dmp R protein and of the DNA sequences from the two Upstream Activation Sequences（UAS）present at the promoter region of the operon were demonstrated using discrete molecular modeling techniques. The best modeled structures satisfying their stereo-chemical properties were selected in each of the cases. To stabilize the individual structures, energy optimization was performed. In the presence of inducers, probable interactions among domains and then the two independent DNA structures with the fourth domain were perused by manifold molecular docking simulations. The complex structures were made to be stable by minimizing their overall energy. Responsible amino acid residues, nucleotide bases and binding patterns for the biodegradation, were examined. In the presence of the inducers, the biodegradation process is initiated by the interaction of phe50 from the first protein domain with the inducers. Only after the interaction of the last domain with the DNA sequences individually, the operon is expressed. This novel residue level study is paramount for initiating transcription in the operon; thereby leading to expression of phenol hydroxylase followed by phenol biodegradation.