Screening And Open Culture Of Methane-Utilizing Mixed Culture With A High Poly-β-hydroxybutyrat Content

Due to the harmful effects of the plastic industry on the environment, biodegradable plastic material and their synthesis technology are more concerned. Poly (β-hydroxybutyrate)(PHB) is one of biodegradable plastics, it has great potential application in the field of plastic materials. PHB not only has the material properties of conventional plastics, but also has biodegradable and biocompatible ability. Much attention is being paid to the biosynthesis of PHB for its applicability. However, one of the problems facing the development of biodegradable polymers is their high price compared with petrochemical derived plastics. Much effort needs to be devoted to develop a process for the economical production of PHB with certain microorganisms.In this paper, Methane was used as sole carbon source to accumulate methane-oxidizing bacteria in an open system. Methane-Utilizing mixed culture with high PHB content was enriched by feast-famine cycle. The method of Sudan black rapid detection was developed to screen mixed culture more efficient. The Methane-Utilizing mixed culture has high tability and methane monooxygenase (Methane Monooxygenase, MMO) activity. The microorganism in mixed culture was studied by plate streaking separation. The results show that Methane-Utilizing mixed culture can use methane, methanol as carbon source to grow and has MMO activity.Methane-Utilizing mixed culture can growth on LB culture medium and can growth by using ethanol as carbon source. However, no MMO activity was found. Through PHB content analysis of each pure strains in the mixed system after separation by cross-scribing, it is speculated that the presence of accompanying bacteria in mixed cultures improve the physiological growth conditions for methanotrophic bacteria and maintain the stability of structure and function. Using this mixed culture as catalyst, propylene can be produced to epoxypropane.The analyses of structure of microorganism show that the mixed culture was composed of methane-oxidizing bacteria and other non-methane-oxidizing bacteria. Copper ion concentration has a certain influence on the growth of Methane-Utilizing mixed culture. With the results of the study in the fermentation tank of Methane-Utilizing mixed culture with shake-flasks, a new one-step fermentation with fermentor, was developed for the PHB production with high concentration and good productivity in a simplified way, which was much superior to the traditional two-step fermentation way.