Study On Preparation Of White-rot Mycelium Pellets And Its Treatment Efficiency To Sulfonamides Antibiotics

Sulfonamides antibiotics(SAs)are one of the earliest and most widely used antibiotics in the world.With high detection frequency and wide pollution range,SAs can persist in the environment and do great harm to human beings,animals and plants and ecosystem.Microbiological method is an economical,practical and effective method to treat SAs without secondary contamination.However,the application of microbiological method is limited by the inhibition of SAs to microorganisms,the low degradation efficiency of SAs by microorganisms and the loss of functional bacteria.In order to solve these problems,obtaining a degradation system of mycelium pellets with good surface properties,easy solid-liquid separation,good tolerance to SAs and degradation efficiency in a short period of time has become the key research direction of this project.Two species of white rot fungi were selected as target strains in this study.One is a model strain of white rot fungus,Phanerochaete chrysosporium,or PC.The other strain was screened from leaf litter and identified as Irpex lacteus(IL)by ITS.I.lacteus had a very developed hyphae structure.The mycelia had tabula and clamp connection,which could form white cotton flocculent colonies,and did not produce spores on solid medium.The hyphae of P.chrysosporium has multiple nuclei without tabula and clamp connection.The mycelium is shorter,and can form spider net white colonies and produce a large number of white powdery conidia.P.chrysosporium grew faster and had more advantages than I.lacteus.However,I.Lacteus had better tolerance to SM2,with a wider tolerance range.In order to obtain white rot mycelium pellets with faster pellet formation and better mechanical efficiency,the pellet formation conditions of two kinds of mycelium pellets were optimized in this study,and the properties of mycelium pellets were characterized.PC mycelium pellets were prepared by spore inoculation culture method.The optimum culture conditions were as follows:pH 6,35℃,160rpm,the inoculum concentration is 10~4per litter,and cultured for 4 days.IL mycelium pellets were prepared by mycelium fragment inoculation and culture method.The optimum culture conditions were as follows:pH 6,30℃,140 rpm,and cultured for 1 day without breaking the mycelia.The properties of mycelium pellets showed that PC mycelium pellets were more uniform in size and more regular in shape,with tighter structure and stronger mechanical properties.The IL mycelium pellets have shorter pellet forming time,higher porosity,larger pore diameter between mycelia,larger specific surface area and stronger adsorption capacity.To investigate the degradation efficiency of two kinds of white rot mycelium pellets to sulfonamides antibiotics.Sulfadimethylpyrimidine(SM2)was used as the target pollutant.The adsorption-degradation experiment results showed that the removal of SM2 by mycelium pellets mainly depended on biodegradation.The optimum degradation conditions of SM2 were investigated.The optimal degradation conditions of SM2 by PC mycelium pellets were 30℃,160 rpm,pH 6,5 g/L glucose.The optimal degradation conditions of SM2 by IL mycelium pellets were 30℃,160 rpm,pH 5,0 g/L glucose.The degradation of SM2 by PC mycelium pellets is a co-metabolic process,and the degradation of SM2 by mycelium pellets can only be started by adding glucose as an additional carbon source,while IL mycelium pellets can directly use SM2 as the only carbon source,and no additional carbon source is needed in the degradation process of SM2.The degradation kinetics study showed that there was a significant difference in SM2 removal rate between PC and IL mycelium pellets.IL mycelium pellets had higher tolerance to SM2 concentration,and the degradation ability was much stronger than PC mycelium pellets.When the initial concentration of SM2 is low,the degradation process is more consistent with the first-order reaction kinetics,and the degradation process of SM2 was limited by the initial concentration of SM2.When the concentration of SM2 increases,the degradation rate increases.When the concentration of SM2 is higher,the degradation process is more consistent with the zero-order reaction kinetics,and the degradation rate did not change significantly with the increase of the concentration of SM2.