Breeding And Application Of Polyvinyl Alcohol-degrading Strain

Polyvinyl alcohol（PVA）is a high-stability,highly emulsifiable,and strongly viscous polymer widely used in fields such as textiles and papermaking.Large amounts of PVA are present in the wastewater from textile printing and dyeing processes,making it difficult to biodegrade and causing environmental pollution.In this study,a strain of Sphingopyxis sp.H3that exhibited high efficiency in degrading PVA was obtained through the process of domestication,screening,and composite mutagenesis breeding.The improvement in the strain’s degradation performance before and after mutation was analyzed.To further extend the practical applications of this discovery,the strain was formulated into a bio-agent for deployment in the treatment of wastewater from textile printing and dyeing processes.Additionally,novel application techniques were also explored in this study.To obtain excellent PVA-degrading strains,directional taming was conducted on the sludge from the aeration tank of a textile printing and dyeing plant,resulting in the isolation of a bacterial consortium capable of efficiently degrading PVA.Through purification and isolation,five single strains capable of degrading PVA were obtained.Among them,Sphingopyxis sp.Q2exhibited the highest degradation efficiency,completely degrading 1 g·L^-1 PVA within 66 hours.Through UV and diethyl sulfate composite mutagenesis,the highly efficient mutant strain Sphingopyxis sp.H3 was obtained,which can completely degrade 1 g·L^-1 PVA within 36 hours and is currently the strain with the highest reported degradation efficiency.To better apply Sphingopyxis sp.H3 in textile dyeing wastewater treatment,it is necessary to explore its performance and the reasons for the improvement of its degradation ability after mutagenesis.Through PVA degradation and kinetic analysis at different initial concentrations,it was found that Sphingopyxis sp.H3 exhibited the highest degradation rate towards 2 g·L^-1 of PVA.The performance of Sphingopyxis sp.H3 was examined under different conditions,including temperature（20-40°C）,p H（4-10）,salt concentration(10-30 g·L^-1),and aniline concentration(0-0.45 g·L^-1),and the degradation rate of 1 g·L^-1 PVA was above 50%,indicating that this strain has good practical application potential.Morphological observations revealed that the mutant strain Sphingopyxis sp.H3 had more dispersed cells and was less prone to clustering compared to the wild-type strain,which was more conducive to full contact with PVA.q RT-PCR analysis showed that the transcription levels of proteins related to extracellular polysaccharide synthesis and secretion were reduced in the mutant strain Sphingopyxis sp.H3,which may contribute to the increased cell dispersal.Furthermore,the transcription levels of key enzymes in the phosphogluconate pathway and TCA cycle were upregulated,enhancing the metabolic capacity of the strain and contributing to the improvement of its degradation ability.The present study focused on optimizing the breeding process of Sphingopyxis sp.H3 and investigating its potential as a bio-agent for waste treatment.Optimization of the breeding conditions revealed that under the following parameters:4%(v·v^-1)inoculum size,400 r·min^-1stirring speed,1.25 v·v^-1·m^-1 aeration rate,and a 5:1 carbon to nitrogen ratio in the supplemented medium,the OD₆₀₀ was increased by 4.5-fold compared to that of shake-flask breeding,while maintaining the unit bacterial mass degradation performance for PVA.The breeding broth was combined with a carrier（rice bran:chitosan:sodium alginate=17:2:1,w/w/w）to prepare a solid-state bio-agent.By exploring the application process of the bio-agent,it was found that four commonly used dyes,Disperse Blue 56,Reactive Blue 194,Methyl Blue,and Rhodamine b,could improve the efficiency of PVA degradation by the strain at appropriate concentrations.Based on this,an application process was proposed whereby waste water of different chromaticity batches would be mixed in a certain proportion before adding the bio-agent.At a dosage of 0.2 g·L^-1,according to the proposed application process,the PVA and COD removal rates were increased by 44.8%and 42.4%,respectively,and the ammonia nitrogen content was reduced by 19.8%compared to the control without bio-agent.These findings provide a solid foundation for the practical application of this bio-agent for treating wastewater in textile dyeing and printing industries.