Recent Advances in The Study of Biodegradability of Polyvinyl Alcohol (PVA)

Polyvinyl alcohol (PVA) is a synthetic polymer compound, which is widely used in textile and paper industries. It is easily soluble in water but difficult to degrade under natural conditions, and is a difficult pollutant to degrade in water treatment. Its content in textile wastewater is very high, and with the continuous development and growth of China's textile industry, it discharges more and more wastewater, which can reach tens of millions of tons. Therefore, it is necessary to realize the biodegradation of polyvinyl alcohol and apply PVA degradation enzyme to the desizing process of textile industry. The biodegradation of PVA in the desizing section has two particular advantages, one is the reduction of PVA waste water discharge and pollution, the other is the avoidance of damage to cotton fibers caused by high temperatures and oxidation during the desizing process.

Microbial degradation of PVA

In microbial degradation studies of PVA, one of the first strains of bacteria capable of producing enzymes that degrade polyvinyl alcohol was obtained in 1973, using PVA as the sole carbon source. In subsequent studies, more researchers have continued to discover strains that can degrade PVA. Among them, Sakazawa et al. developed symbiotic PVA-degrading bacteria that required the provision of the biogenic factor PQQ to achieve degradation of polyvinyl alcohol. Other strains have been developed that require the addition of additives such as tyrosine and leucine to degrade polyvinyl alcohol.

Studies have shown that microorganisms capable of degrading polyvinyl alcohol are poorly distributed in nature and are usually found and extracted from PVA-contaminated environments. Therefore, it is important to use PVA as the only carbon source for the screening medium in order to screen for PVA-degrading microorganisms in a stressed environment. It has been suggested that PVA oxidase produces hydrogen peroxide, which is toxic to microorganisms, resulting in a decrease in the number of microorganisms and only a few surviving to obtain PVA-degrading strains.

In order to enhance the degradation effect of bacteria and achieve complete degradation of polyvinyl alcohol, Chiellini et al. argued for the domestication of mixed bacterial flora to improve the efficiency of degradation and achieve complete degradation of polyvinyl alcohol, a polymer. They cultured a mixed bacterial system from sludge generated from paper mill wastewater treatment, domesticated it and then studied its properties for PVA degradation. The study showed that the bacterial mixture, the degradation ability of polyvinyl alcohol is not greatly affected by the degree of polymerization of PVA, but is closely related to the degree of alcoholysis. For the same degree of polymerization of polyvinyl alcohol, the hybrid system has a significant delay period for degradation of polyvinyl alcohol with high alcoholysis degree.