Isolation And Identification Of A Highly Efficient Phenol-degrading Fungus And Its Application As Bioaugmentation Inoculum In Wastewater

Phenol is one of the toxic and refractory organic pollutants in the wastewater of pharmaceutical,coking,papermaking,plastic and other industries.With the continuous development of the economy and society,the pollution of phenolic wastewater is becoming more and more serious,which poses a serious threat to the ecological environment.Biological treatment of phenol containing wastewater has a broad application prospect owing its low cost and no secondary pollution.In this paper,activated sludge from aerobic treatment section of a paper mill in Shaanxi Province was selected as the research specimen,and the dominant microbial community with high phenol tolerance threshold was obtained through stepwise domestication and isolation.The phenol degrading ability of 8 strains were further investigated,and a strain with high phenol tolerance and high degradation efficiency was selected and named QWD1.The morphological feature,ITS r DNA gene sequence and phylogenetic tree indicated that QWD1 was a filamentous fungus belonging to the Magnusiomyces capitatus.Then,the mechanism of phenol degradation was preliminarily explored.It was speculated that the pathway of QWD1 degradation phenol was belonged to the ortho-open looped mode by testing the activity of phenol-degrading enzymes catechol 1,2-dioxygenase and catechol 2,3-dioxygenase of QWD1.The degradation potential of microbes to the toxic and refractory compounds is strongly influenced by different factors such as nutrients,pollution loads and physicochemical cultivation conditions.Therefore,the influencing factors for bioremediation need to be optimized to obtain the best removal effect.Optimization of parameters including nitrogen sources,inoculum concentrations,p H,temperatures,and nitrogen source concentrations had improved the phenol degradation efficiency of strain QWD1 to some extent,the threshold of phenol tolerance in liquid culture medium could reach 1600 mg/L.The optimization results showed that the optimal degradation conditions for strainQWD1were?NH₄?₂SO₄asnitrogensource,inoculum concentration 15%,p H 7,temperature 35°C and nitrogen source concentration 14 mmol/L.Under these conditions,the removal rate of phenol was up to 97.15%in 28 hours.Then,the selection of the carrier and the suitable preservation temperature of the QWD1 bioaugmentation inoculum were preliminarily studied.By comparing the adsorption effect of the inorganic carriers?vermiculite,kieselguhr?with the organic carriers?wheat bran,cavings?on the fungal liquid and the preservation effect after preparation of the bioaugmentation inoculum,it was found that the cavings had a high water absorption and a better adsorption effect of QWD1,and the p H range of the bioaugmentation inoculum during the long-term storage process was small,and the preservation time was longer.At the same time,aftercomparingthepreservationeffectofdifferent bioaugmentation inoculum at 4°C and normal temperature,it was found that the preservation effect at 4°C was better than at normal temperature,and the preservation time of the bioaugmentation inoculum prepared with cavings as carrier at 4°C could reach 90 days or even longer,the number of viable fungi was about 2.5×10⁸ cfu/g.The treatment effect of phenol-containing wastewater was also better than other bioaugmentation inoculum,and the removal rate of phenol could reach 100%at 24 hours,which presented a good application potential.Finally,the effects of adding bioaugmentation inoculum on simulated sludge-containing wastewater treatment by activated sludge and the effect on microbial community structure were investigated.It was found that the addition of phenol-reducing bioaugmentation inoculum could significantly improve the treatment effect of activated sludge on phenol-containing wastewater,shorten the time required for complete degradation of phenol,and increase the COD removal efficiency and total removal rate.The optimum dosage of the obtained microbial agent was 4 g/L,the phenol with a concentration of 1600mg/L could be completely degraded at 24 hours,and the removal rate of COD could reach 94.7%in 60 hours.The high-throughput sequencing technology was used to analyze the microbial community structure in bio-enhanced and non-enhanced activated sludge.It was found that the addition of phenol-reducing bioaugmentation inoculum could increase the abundance and diversity of bacteria and fungi in the wastewater treatment process of reactors.The added QWD1 belonging to Magnusiomyces could be the dominant strain in the intensification treatment system.The addition of bioaugmentation inoculum not only enlarges the population size of microorganisms involved in phenol metabolism,but also effectively improves the microbial diversity in the later stage of the treatment system,and was conducive to the further formation of a stable microbial ecosystem.