Degradation Effects Of Microalgae And Microalgae-bacterial Consortium On Environmental Hormone Nonylpenol

As a main material in the synthesis of nonionic surfactant nonylphenol polyethoxylates,Nonylphenol(NP)has been widely used in various industries such as papermaking,textile,rubber,pesticide and detergent,and released into environment.NP has been reported to possess strong estrogenic activity and high bioaccumulation.It is one of the representative endocrine disrupting chemicals and persistent toxic pollutants threatening stability of human health and ecosystems.The main purpose of this paper is to conduct research on the isolation of NP degradating microalgae and bacteria,and explore the functions and effects of microalgae and microalgae-bacterial consortium of NP degradation.The result of this research will provide experimental foundation for seeking and optimizing NP ecological degradation mode,and scientific basis for ecological restoration of NP or other toxic analogs in NP polluted water area.Six microalgae were isolated from Guangzhou section of the Pearl River.All of them could degrade NP,including five green algal(Scenedesmus obliquus,Scendesmus quadriauda,Chlorella vulgaris,Selenastrum bibraianum and Ankistrodesmus acicularis),and one cyanobacteria(Chroococcus mjnutus).Four biodegradtion bacteria were isolated,Pseudomonas sp.SW-1,Pseudomonas sp.ZL-2,and Pseudomonas stutzeri XQ-3 were isolated from the phycosphere of S.quadriauda,A.acicularis and C.vulgaris,respectively.Cupriavidus sp.EB-4 were isolated from the water body of NP pollution.The six microalgae were cultivated with the presence of the pollutant(NP)at different concentrations.The content of Chorophyll a,fluorescence transient(Fv/Fm),and antioxidant enzyme systems,including superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)were choosed to clarify the microalgae tolerance capacity to nonylphenol.And the tolerance capacity of C.vulgaris was highest,however,and C.mjnutusi was lowest.There were no significant differences among the other four microalgae.Six typical microalgae had rapid and high ability to absorbed and degraded NP,and the NP residual content appeared a decrease trend with the biomass of microalgae increased in the culture.After 5 days culturing,the percentage range of six microalgae bioaccumlated(absorbed NP on the algal cells and absorbed in algal cells)the NP from 7.86% to 30.13% in the cultures,and the biodegradation percentage of NP were from 34.91% to 65.63%.Extracellular NP contents of six microalgae were lower than intracellular NP contents,with the ratio changing from 0.04 to 0.85.The absorbed NP on the algal cells and absorbed in algal cells were maximum in the first day,then with the increase of incubation time,NP of extracellular and intracellular of algal cells appeared decrease trends while the algae biomass increased.These results demonstrated potential application of six algae species in the degradation of the organic contaminant alkylphenol.The biodiversity of the main bacteria presented in the culture of three microalgae was revealed by the Illumina Miseq high throughput sequencing method.According the results,there were eleven kinds of associated bacteria,including Limnobacter sp.,Sphingomonas sp.,Brevundimonas sp.,Methylobacterium sp.,Acidovorax sp.,Pseudomonas sp.,Methylophilus sp.,Sphingopyxis sp.,Porphyrobacter sp.,Flavobacterium sp.and Verrucomicrobium.And Pseudomonas sp.,Sphingopyxis sp.,Porphyrobacter sp.and Flavobacterium sp.were the dominant genera,accounting for 57.7%~96.0% in the associated bacterial community,and they have strong biodegrade abilities to organic pollutions.Whether microalgae existed or not had a significant effect on microalgae associated bacterial community.Three associated bacteria SW-1?ZL-2?XQ-3 and one exogenous bacteria EB-4 could utilize NP as the sole carbon source.The NP residue contents showed a decreases trend with the biomass of bacterial strain increased in the medium.The NP removal progress of four strains can be fitted to the first-order model,with the degradation rate varied from 0.1247d-1 to 0.3000d-1.Three associated bacteria were used to combined with their algae formed three algal-bacteria consortium named S-SW,A-ZL and C-XQ,and the exogenous bacteria EB-4 consortia construction with S.quadriauda that formed algal-bacteria consortium named S-EB.The synergistic relationships in the microalgae-bacterial consortium were clearly demonstrated,since for the removal percentage of NP in the treatment group of S-SW and S-EB were higher than only algae and only bacteria groups.The NP removal progress of four algal-bacteria consortium could be fitted to the first-order model,and the degradation rate showed in the following order: C-XQ(0.3960 d-1)>S-SW(0.3506 d-1)>A-ZL(0.1968 d-1)>S-EB(0.1776 d-1).