Oriental Plans To Branch Acid Bacteria Producing Polylactic Acid Degradation And Protease

With the development of the world economy, the environmental condition has been deteriorating by the widespread use of petroleum-derived products, and concerns about environment protection have never been as strong as today. In order to solve the problem of synthetic resin and fiber's strong resistance to degradation when released into the environment, the research of biodegradable plastics has gained enormous attention. PLA is considered to be one of the most promising materials. But compared with research in PLA synthesis, research in the degradation of PLA is relatively lagging behind. PLA is decomposed very slowly in nature, and the distribution of microbials and enzymes capable of accelerating the degradation of PLA is limited. This, to larger extent, also impedes clarifying the mechanism of the PLA degradation and confines the development and application of the controllable degradation of materials such as PLA.We isolated an actinomycosis strain from our culture collections for its high degradability of PLA. This strain was identified as Amycolatopsis orientali. Further results showed that, among others, geltin was one of the best inducer for inducing the strain to produce PLAases with the enzyme producing peak appearing at 50 hours after incoculation. In accordance with the fact that gelatin usually acts as an protease inducer, the fermented protease activities also reached the highest level of 29,000U/L roughly slightly around 65 hours. In addition, primary-characterization of the crude enzymes from the culture supernatant showed that both protease activities and PLA-degrading activityies were relatively stable within an alkaline pH range (pH 8 to 10 ), implicating a potential relationship between produced protease activity and PLAase activity.Five protease components were isolated and purified form the fermented culture, with three of them displaying PLA-degrading activities. Characterizing the substrate specificity of both crude purified enzymes revealed that the protease activity and the PLAase activity from the fermented culture was not strictly correlative, namely, not all the proteases have the ability to degrade PLA. But the simultaneous isolation of three PLA-degrading activities from one strain suggested a common feature not being shared by other proteases exist in these enzymes. Finally, methods to analyze the hydrolytic products formed by PLAase-catalyzed reactions,were exploited, which should be very useful for further elucidating the mechanism of enzymatic degradation of PLA.