Study On The Conditions Of Microbial Degradation Of Poly(Vinyl Alcohol) And The Mechanism Of The Degradation Process

Poly(vinyl alcohol) (PVA) is widely applied in the textile as a sizing agent. But the cotton fabrics treated by PVA must be desized to enhance their water absorbency. In conventional desizing method, the cotton fabrics are washed with hot water and sometimes oxidant such as NaBrO2, etc. is used to remove PVA. Thus, the wastewater from the textile plant contains abundant PVA and oxidant agents. If PVA-degrading enzymes were used in the desizing process, the PVA concentration in the wastewater could be decreased. At the same time, the damage of cotton fabrics by high temperature and chemicals could be avoided. The investigation of PVA microbial degradation conditions and the mechanism of the degradation process can be helpful for the screening of effective strains for PVA degrading, thus enhance application of PVA-degrading enzymes in the desizing process. It is very important to relieve environment pollution in the textile industry.In this study, the conditions for biodegradation of PVA by Penicillium sp. WSH02-21, Streptomyces venezuelae GY1 and a mixed culture were investigated, respectively. The processes and mechanism of PVA degradation by these strains were studied via high performance liquid chromatography (HPLC), high performance gel filtration chromatography (HPGFC), infrared spectrometer (IR) and terminal restriction fragment polymorphism (T-RFLP). The major results are summarized as follows:1) The nutritional conditions for the production of PVA-degrading enzyme by Penicillium sp. WSH02-21 were investigated and the results showed that the strain did not produce PVA-degrading enzyme in the normal fungal media. When 1 g/L of soluble starch was used as sole carbon source and yeast extract as nitrogen source, very small amount of PVA-degrading enzyme was produced by the strain. When PVA was used as the sole carbon source, however, PVA-degrading enzyme activity and the specific enzyme activity increased significantly. It indicated that the PVA-degrading enzyme produced by Penicillium sp. WSH02-21 was inducible.The effects of the 20 amino acids and some vitamins on the production of PVA-degrading enzyme by WSH02-21 were investigated in the synthetic medium using NH4Cl as the nitrogen source. The results showed that threonine is a necessary amino acid for PVA-degrading enzyme production by Penicillium sp. WSH02-21.