Screeing And Identification Of Salt Tolerant Strains In Cotton Pulp Wastrwater And Biodegradation Experiment

The viscose fiber industry used cotton pulp through chemical and mechanical processing to produce a large amount of high-concentration organic wastewater containing cellulose,hemicellulose and lignin.The salt content of this wastewater after acid neutralization was greatly increased.Cellulase-producing microorganisms can catalyze the hydrolysis of cellulose to glucose.The special marine environment can provide salt-tolerant microorganisms adapted to extreme environment.The treatment of saline cellulose wastewater from the perspectives of recycling and biologicalization was of great significance to human sustainable development.A salt-tolerant bacterium capable of producing cellulase was domesticated from the enrichment solution of bottom mud in Qingdao offshore and cotton pulp wastewater.It was identified as Bacillus paralicheniformis by physiological and biochemical identification and 16S rRNA sequence.The cellulase content of this strain produced by liquid fermentation at 35?and 150 r/min were FPase 0.136 U/mL,CMCase 0.123U/mL and?-glucosidase 0.103 U/mL and the cellulase activity was stable in 1?4%NaCl solution.The optimal culture medium and condition of fermentation were study.The results determined that the optimal carbon source and nitrogen source were corncob and yeast extract,the optimal KH2PO4 addition amount was 0.4%,the optimal initial pH of the culture solution was 7,the optimal fermentation temperature was 35?and the optimal fermentation time was 60 h.After optimized culture,the cellulase-producing ability of the strain was increased by 48.9%.The endonuclease properties of the enzyme solution after fractional precipitation of ammonium sulfate were investigated.CMCase showed good relative activity in 1?5%NaCl solution,pH 4.5?8.5 reaction condition and 50?water bath.Mg²⁺?Co²⁺?K⁺can promote the production of endonuclease.This endonuclease exhibited salt resistance,acid and alkali resistance,and heat resistance.The 8%inoculated amount of bacterial suspension was directly inoculated into cotton pulp wastewater with CODCr of 1090 mg/L and pH of 7.After 9 days,the best CODCr removal rate was 64.8%and the degradation kinetic model of organic matter conformed to the first-order kinetic equation.The composition of cotton pulp wastewater before and after biodegradation was analyzed by GC-MS and it was found that organic pollutants dominated by biphenyl compounds and ester compounds were degraded into small molecular benzene series and short-chain alkanes through carbon bond breaking,hydrolysis reaction and ring opening reaction.The desalination rate of the biologically degraded wastewater after treatment by electrodialysis was 44%.