The s-oph enzyme for efficient degradation of polyvinyl alcohol: soluble expression and catalytic properties

Polyvinyl alcohol (PVA) is one of the most widely used water-soluble polymers with remarkable mechanical properties. However, water-soluble polymers are among the major organic pollutants of streams, river, and marine ecosystems. Once dispersed in aqueous systems, they can directly interfere with the life cycle of aquatic organisms via direct toxic effects. There is thus an urgent need for microorganisms or enzymes that can efficiently degrade them. Oxidized PVA hydrolase plays an important role in the pathway of PVA biodegradation. It is the key enzyme in the second step of the pathway for complete degradation of PVA.

The s-oph gene was cloned from the laboratory-isolated strain Sphingopyxis sp. M19. This gene was expressed in the Escherichia coli system pET32a/s-oph expression vector, with the products forming an inclusion body. By binding with a molecular chaperone, pET32a/s-oph/BL21 (DE3)/pGro7 was successfully constructed, which enabled the s-oph gene to be solubly expressed in E. coli. The protein encoded by the s-oph gene was purified at a yield of 16.8 mg L^-1, and its catalytic activity reached 852.71 U mg^-1. In the s-oph enzyme reaction system, the efficiency of PVA degradation was increased to 233.5% compared with that of controls.

The s-oph enzyme exhibited the characteristics of being able to degrade PVA with high efficiency, specificity, and stability. This enzyme has good potential for practical application in ameliorating plastic pollution and protecting the environment.