Isolation And Characterisation Of Thermophilic Polyvinyl Alcohol Degrading Bacteria

Polyvinyl alcohol(PVA)is widely used in textile,printing and dyeing,chemical fiber and other industries because of its good adhesion,wear resistance and chemical stability.However,the use and discharge of large amounts of PVA also cause serious pollution to water bodies and soil ecosystems.Although PVA is biodegradable,most microorganisms have low PVA degradation rate with long times.The thermophilic bacteria could promote the biodegradation of organic pollutants using thermophilic enzyme with thermostability and high catalytic reaction rate.Therefore,it is of great significance to isolate the thermophilic bacteria with high performance of PVA biodegradation,and study their degradation characteristics and mechanism for the construction of efficient PVA pollution remediation technology,reducing PVA pollution and its harm to ecological environment.In this study,high-rate thermophilic PVA-degrading bacteria were isolated from hightemperature compost,and the performance and mechanism of PVA biodegradation were studied.The main conclusions of the paper are as follows:1.Two thermophilic bacteria with PVA-degrading capacity were isolated from the compost samples and designated as FAFU 038 and FAFU 039 respectively.Gram staining and microscopic observation showed that both of these strains were Gram-positive rod-shaped bacteria.16 S r RNA gene identification results showed that FAFU 038 strain belongs to Brevibacillus aydinogluensis,and FAFU 039 belongs to Brevibacillus thermoruber.Besides,Both strains have good PVA degradation ability,of which FAFU 038 has better PVA degradation ability than FAFU 039,and the growth of the bacteria is good under the condition of PVA concentration of 1 g / L.2.The degradation performance of thermophilic bacteria FAFU 038 under different conditions was investigated.The results showed that the concentration of PVA was 0.05 g / L,the degradation temperature was 55 ?,the p H value was between 7-8,and the Na Cl concentration was below 1 g / L.The thermophilic bacteria FAFU 038 cultured with yeast powder as the nitrogen source has the best degradation rate of PVA,and can degrade the PVA of 0.05 g / L by more than 90 % within 120 h.In addition,the study found that the degree of PVA polymerization also has a greater impact on the growth and degradation rate of FAFU 038.The lower the degree of polymerization,the more conducive to FAFU 038 growth and PVA degradation rate.3.Based on the above experiments,this study further explored the degradation mechanism of FAFU 038 on PVA.The results of ultraviolet spectroscopy and gel chromatography analysis showed that the molecular weight of PVA gradually decreased after being degraded by thermophilic bacteria FAFU 038.FTIR and three-dimensional fluorescence spectroscopy analysis indicate that PVA degradation products may be aldehydes,ketones and other small molecules containing specific functional groups(carbonyl,hydroxyl,carboxyl,etc.).In addition,studies on FAVA038 strain PVA degrading enzymes and their reaction kinetics have shown that the oxidase and dehydrogenase secreted inside and outside the thermophilic bacteria play a major role in PVA degradation.Among them,the extracellular enzyme activity accounted for 45.02 %,and when the PVA concentration was close to 4 g / L,the PVA degrading enzyme could reach the maximum reaction rate(V = 7.18 U / min).