Screening Of PVA-degrading Enzymes Producing Microorganism, Fermentation Optimization And The Enzymatic Application In Desizing

Polyvinyl alcohol (PVA) is a kind of water-soluble synthetic macromolecular polymer. It waswidely used in the textile as a sizing reagent. In pretreatment of textile, the sizied cotton fabricsmust be desized to increase water absorption.In traditional desizing method, cotton fabrics were washed with hot-water (70~90℃) toremove PVA, which caused environmental pollution due to the low biodegradability of PVA. WhilePVA could be partially degraded during the enzymatic desizing process. The potential advantages ofenzymatic desizing process included less wastewater treatment cost, more energy and water savings,and the quality improvement of textile products. In this study, the biologica1 diversity index wasused to access species richness in different sampling spots during the screening of PVA-degradingenzymes producing microorganisms. The identification of a high-yield PVA-degrading enzymesstrain, its nutrients and environmental conditions were studied and the characteristics of thePVA-degrading enzymes were investigated. Furthermore, the potential application of this novelPVA-degrading enzymes in the process of cotton fabrics desizing was evaluated. The main resultswere given as follows:1. Results of the biologica1 diversity index indicated that the microorganisms which could producePVA-degrading enzymes were extensively and universally distributed in nature.2. A high-yield PVA-degrading enzymes producing bacterium which was able to use polyvinylalcohol (PVA) as sole carbon source was isolated. 16S rDNA and cell morphology, physiologyand biochemistry showed that it belonged to Janthinobacterium sp.. So far, this was the firstreport of PVA degradation by a strain of Janthinobacterium sp.. This strain was found to mostlyproduce the inducible PVA-degrading enzymes, and a majority of which was extracellularenzymes.3.PVA degradation mechanism of Janthinobacterium sp. WSH04-01 was similar to that of otherreported bacteria. PVA was degraded by PVA oxidase and β-diketone hydrolase successively.4.The optimized seed culture medium contained (g/L): corn starch 20, Yeast-extract 5, K2HPO4 1.6,KH2PO4 0.2, MgSO4 0.05, CaCl2 0.05, FeSO4·7H2O 0.02 and NaCl 0.02. The optimizedfermentation medium contained (g/L): PVA 10, Glucose 3, Yeast-extract 6, K2HPO4 2,KH2PO40.25, MgSO4 0.03, CaCl2 0.05, FeSO4·7H2O 0.02 and NaCl 0.02 at pH 7.2. The suitable volumesize of medium in 250 ml flasks was 30 ml and the inoculum size was 8% with seed age of 12 h.The cultivation time was 21 h.5.The suitable pH and temperature for PVA-degrading enzymes produced by Janthinobacterium sp.ranged from 5.0 to 7.0, and from 35℃ to 50℃, respectively. The enzymes were relatively stableat 35℃. Mg2+, Al3+, Ca2+, Fe2+, Ba2+, Hg+ and Mn2+ were the activators of the enzymes and Cu2+,Ni2+, Hg2+, Zn2+ and Sn2+, especially Hg2+ and Cu2+, inhibited the enzymes activity.6.Compared to the hot-water (80℃) desizing process in which 80% of PVA could be removed fromcotton fabrics in 1 h, it took 3 h to get rid of 80% of PVA from cotton fabrics. However, duringthe enzymatic desizing process, PVA was partially degraded and the biodegradability of PVA inwastewater was increased.