Study On The Clearance Of Phenol In Water By Seeds And Root Attached Rhizosphere Microorganisms Of Polygonum Orientale Linn.

Phenol(commonly known as carbolic acid,C6H5OH),a high toxic substance,is listed as one of the major pollutants around the world,which would cause severe pollution in water as well as in environment,leading to the death of various organisms including fishes and plants,eventually threathening human life.Plant-microbial combination methods show many advantages in removal of various pollutants from water.Polygonum orientale is a widely distributed hydrophyte,which is common used as landscape plant,indicating its phenol clearance potential.Here,in order to examine the potential phenol clearance using Polygonum orientale,first the phenol tolerance of P.orientale seeds and seedlings have been evaluated.Second,two fungi strains from rhizosphere microorganism of P.orientale,which could degrade phenol was isolated and identified.The phenol clearance ability of the identified fungus and P.orientale-fungus have been examined.(1)Although the germination and seedling growth of the P.orientale were affected when phenol concentration >5mg/L,P.orientale still could survive at this level.The seeds of P.orientale germinated normally at the phenol less than 160 mg/L and the seedlings grew unaffectly at the phenol less than 80 mg/L.Intestingly,phenol at 5mg/L promoted the seeds germination and seedlings growth.(2)Two fungi,named as YYR7 and strain YYR29,were isolated and identified from the rhizosphere microorganism of P.orientale in Taiyuan section of Fenhe scenic.Both of them produced laccase which could degrade phenol.The laccase activity from YYR7 was higher than that from YYR29,up to 1.91 U/L.The strain YYR7 was identified as Talaromyces verruculosus,based on the morphological and molecular characteristics by Neighbor-Joining(NJ)method,Bayesian method and Maximum likelihood(ML)method.(3)As higher lactase activity,the YYR7 was selected for phenol clearance assay furtherly.Our results showed that two days culture of YYR7 presented highest phenol clearance ability,degrading 300mg/L.The pH 4.5-5.5 was optimal condition for phenol degradation by YYR7,though it grows at pH4.5-7.The maximum tolerance of phenol concentration for YYR7 was 700 mg/L to 800 mg/L.The phenol could be completely cleared in 4 days at the initial concentration below 600 mg/L.(4)Comparing with P.orientale seedling treatment alone,the plant-microbe combination showed 1.85 times clearance of the phenol at 20 dpt(days post treatment)with the initial concentration at 160 mg/L.Both plant alone and plant-microbe combined treatment removed 95 % phenol within 30 days treatment.However,the seedlings of P.orientale without YYR7 were impaired by phenol according to morphological and physiological index.These data suggested that P.orientale combined with YYR7 treatment is more efficient and less toxic to plant itself.Take together,it is concluded that P.orientale is a potential excellent biological material for phenol removal in polluted water body.The laccase producing strain,the YYR7,one rhizosphere microorganism of P.orientale,could efficiently help in phenol clearance together with P.orientale.Our study provide a valuable and pracital model for decontamination of phenol polluted water body.