Isolation Of A Mixed Culture For The Degradation Of Poly(Vinyl Alcohol) And Optimization Of Culture Conditions

Polyvinyl alcohol (PVA) is a kind of water-soluble synthetic macromolecular polymer. It was widely used in the textile as a sizing reagent. In pretreatment of textile, the sizied cotton fabrics must be desized to increase water absorption. In traditional desizing method, cotton fabrics were washed with hot-water (70⁹0℃) to remove PVA, which caused environmental pollution due to the low biodegradability of PVA. While PVA could be partially degraded during the enzymatic desizing process. The potential advantages of enzymatic desizing process included less wastewater treatment cost, more energy and water savings, and the quality improvement of textile products.In this study, a mixed culture, which could degrade 1 g L-1 poly (vinyl alcohol) (PVA) completely, was screened from a soil sample, the nutritional conditions, the characteristics of the PVA degrading enzymes (PVAase) and the purification of PVAase were investigated. The enzymatic desizing test was also analyzed. The main results were given as follows:(1) A mixed culture, which could degrade 1 g L-1 poly (vinyl alcohol) (PVA) completely, was obtained from a soil sample from Junda Textile Factory. It takes about two days to degrade 1 g L-1 poly (vinyl alcohol) completely. 53% of PVAase are extracellular enzymes.(2) Three strains were isolated from the PVA-degrading microbial population through dilution method. Among them, two belong to bacteria and one is mould. One of the bacteria and the mould could produce extracellular PVA-degrading enzyme, but none of them could degrade PVA completely alone.(3) The optimized fermentation medium contained (g/L): PVA 205 4, Yeast-extract 3, NaNO₃ 2, K₂HPO₄ 1.6, KH₂PO₄ 0.2, MgSO₄·7H₂O 0.4, CaCl₂ 0.05, FeSO₄·7H₂O 0.02 and NaCl 0.02 at pH 7.2.(4) PVAase was separated by ammonium sulfate fractionation and DEAE-cellulose.(5) The suitable pH and temperature for PVAase produced by mixed culture ranged from 6.0 to 8.0, and from 30℃to 40℃. The optimal pH and temperature for enzymatic reaction were 7.0 and 35°C, respectively.(6) During the enzymatic desizing process, PVA must be swellen.PVA was partially degraded and the biodegradability of PVA in wastewater was increased.