Preparation Of Immobilized Mycelial Pellets And Its Application In Degradation Of Dyes

Triphenylmethane dyes contain complex aromatic ring structures with high chemical stability and low biodegradability,which can accumulate in wastewater and cause serious surface water and groundwater pollution.In recent years,many studies at home and abroad have shown that biosorption-degradation is one of the most promising wastewater treatment methods,which has the advantages of high efficiency,safety,low cost and no secondary pollution.The treatment of dye wastewater by immobilized microbial technology is a new biological treatment method,but there are few reports on the degradation of triphenylmethane dye wastewater by using hyphae as an immobilization carrier.In this paper,10 strains of highly efficient degradation dyes were screened by guaiacol method,which were L-1,L-2,L-3,L-4 L-5,L-6,L-7,L-8,L-9 and L-10.The fungal mycelium was used as the immobilization carrier to immobilize the bacteria with high efficiency to degrade the dye to form a fungal-bacterial immobilization system.The adsorption performance and adsorption mechanism were studied in depth.The immobilized composite system was applied to the wastewater treatment of triphenylmethane dyes by designing the optimal strain immobilization conditions and the conditions for producing ligninase.At the same time,the degradation mechanism of immobilized mycelium on the crystal violet dye wastewater was also discussed.The research mainly yielded the following results:1?Ten strains of ligninase-producing strains were isolated from the soil samples of Xinglong Mountain in Lanzhou,namely L-1,L-2,L-3,L-4,L-5,L-6,L-7,L-8,L-9 and L-10.The laccase activity of strain L-3 and strain L-6 was higher,9.69 U/L and 7.39 U/L,respectively.The L-3 strain was identified as Aspergillus fumigatus by morphological identification and ITS,and the L-6 strain was identified as Pseudomonas fluorescens by morphology and 16S rDNA.2?The fungus Aspergillus fumigatus mycelial pellets was used as a carrier to immobilize Pseudomonas fluorescens with high lignin-producing ability to form fungal-bacterial immobilized mycelium.The immobilized mycelium was used as the research object,and different carbon sources and its concentration were explored,nitrogen source and its concentration,inoculum size,pH value on the formation of pellets and enzyme production.The optimal conditions for forming the mycelial pellets were obtained:sucrose was used as the carbon source,the sucrose concentration was 10 g/L,NH₄Cl was used as the nitrogen source,the concentration of NH₄Cl was 2 g/L,the initial pH of the medium was 6,and the inoculation amount of the fungus was 1 mL.The inoculum size of the bacteria was 3 mL,and the culture was carried out for 3 days under the optimal culture conditions,and the diameter of the mycelial pellets was the largest,about 6.45 mm.At this time,the immobilized mycelial pellets was moderate in diameter,the surface was fluffy,and the elasticity was good.The optimal enzyme production conditions were obtained:sucrose as carbon source,sucrose concentration 10 g/L,NH₄Cl as nitrogen source,NH₄Cl concentration 2 g/L,pH=6,laccase activity up to 16.43 U/L,pH 5,the maximum lignin peroxidase activity is 106.32 U/L,the pH of 4,manganese peroxidase activity is 95.89 U/L,the results showed that the two bacteria in the production of enzymes that the synergy played a role in the process.It is known by SEM observation that the inside of the mycelial pellets is densely entangled and has a large specific surface area,which is favorable for mass transfer and oxygen transmission.3?The prepared immobilized mycelial pellets were put into the triphenylmethane simulated dye wastewater,and the effects of different temperatures,time,pH value,rotation speed,initial dye concentration and reuse on the dye wastewater were investigated.The results showed that in the absence of any nutrients,the temperature was 30°C,the rotation speed was 160 r/min,the inoculation amount was 3 g/100mL,and the pH was 7,the degradation rate of the immobilized mycelium to the crystal violet dye wastewater could reach 99.98%.The degradation rate of malachite green was 96.57%at pH 5.The immobilized mycelium sphere was reused five times under the same conditions,and the degradation rate was still 80%.It is indicated that the triphenylmethane dyes have different degrees of degradation due to their different structures.At the same time,the degradation rate of the crude enzyme solution can reach more than 70%.In addition,the dye is analyzed by using an organic solvent and an inorganic solvent.As a result,the desorption rate of the dye by the organic solvent is as high as 40%or more,and the desorption rate of the inorganic solvent is about 8%.The main force of immobilized mycelial pellets on the degradation of triphenylmethane dye wastewater is that the hydrophobic interaction is not electrostatic.In order to understand the degradation performance of immobilized mycelium on triphenylmethane dyes,the subsequent work of this paper takes crystal violet as the research object and conducts in-depth research.4?The crystal violet was used as the research object.The properties of the immobilized hyphae after treatment of dye wastewater were studied.The products of 2,8 and 14 h were studied by UV-vis spectroscopy,and the main peaks at 2-8 h were found.It is proportionally reduced,indicating that the immobilized mycelium is adsorption process for crystal violet.At14h,the main peak disappears completely,indicating that the immobilized mycelium sphere is biodegradation process for crystal violet.It is shown that the characteristic peak disappears at 589 nm with the conjugated triphenylmethane chromophore,indicating a biodegradation effect.The FT-IR results show that the hydroxyl group participates in the chemical reaction and has the formation of phenol.The LC-MS results showed that the residual amount of crystal violet was 0.2530?g/mL,and the determination of crystal violet indicated that the qualitative result of LC-MS was reliable.The results of GC-MS showed that there are four kinds of crystal violet degradation products,which can be presumed to be two possible degradation pathways.The first one is crystal violet after a series of enzymatic hydrolysis and chemical reaction to form 2,4-di-tert-butylphenol.Open-loop degradation to undecane.The other is that the crystal violet is first decomposed into erucamide and then further degraded to undecane.Studies have shown that the degradation of triphenylmethane dye wastewater by immobilized mycelium is first degraded after adsorption.Due to the different chemical surface structure of dyes,the degradation rate is different.Lignin plays a major role in the degradation process.Force is a hydrophobic interaction that is not electrostatic.The two strains played a synergistic role in the degradation process to open the crystal violet ring to form a low-toxic small molecule.