Construction Of A Co-cluture Consortium For Medium Chain Length Polyhydroxyalkanoate Biosynthesis With The Mixture Of Glucose And Xylose

Polyhydroxyalkanoate(PHA)is a polyester of hydroxyalkanoates which can be fully synthesized by microorganisms and has many high value-added properties such as biodegradability and biocompatibility.The further development and application of PHA were limited by the high cost and small application range.Thus,one of the hot spots in the field of PHA research was reducing production cost and synthesizing PHA with a larger application range.Based on this,this study aims to produce medium chain length polyhydroxyalkanoate(mcl-PHA)with renewable resources including the mixture of glucose and xylose and lignocellulosic hydrolysate.The co-culture consortia consisting of P.putida KT2440 and E.coli MG1655 was constructed.In E.coli,the pts G and man Z genes were knocked out,which prompted it to preferably utilize glucose and slowly utilize glucose.Consequently,reduced the growth competition.Besides,promoted it ability to synthesize acetate and extracellular free fatty acids(FFA)which can promote mcl-PHA synthesis by knockout of atp FH and env R genes.P.putida is able to utilize acetate which can relieve the inhibition of acetate on E.coli,sequentially,formed a mutualistic relationship with E.coli based on "nutrition supply" and "detoxification".In addition,the acetate assimilation of P.putida was enhanced,including overexpression of acs and ack A-pta pathways.The acs overexpressing P.putida KT2440 showed a remarkable increase of mcl-PHA titer(+92%)compard with wild-type P.putida.In M9 medium,total sugar 20 g/L(glucose: xylose,1:1),the co-culture consortia showed a remarkable increase of mcl-PHA titer(+290%)compard with pure culture.The corn straw pretreated with ammonia was hydrolyzed and the main sugar component in the hydrolysate was glucose and xylose(4.3:1).The titer of mcl-PHA produced by co-culture with hydrolysate was 0.434 g/L which was slightly lower than the titer produced with reagent sugar(0.469 g/L).The above results have a competitive advantage compared with other studies using synthetic resources to synthesize mclPHA,indicating that the co-culture method is an effective strategy to enhance the synthesis of mcl-PHA with sugar-based carbon sources.