Study On Metabolic Engineering Of H.bluephagenesis Utilizing Xylose

White pollution is eroding the earth's ecological system and plastic restriction orders are also being promulgated and implemented in more and more countries.Biodegradable materials have become an essential p art of the sustainable development of human society.Polyhydroxyalkano ates(PHA)is a series of biopolyesters that are degradable,environment ally friendly and biocompatible.Among them,poly-3-hydroxybutyrate(P-HB)is a polyhydroxyalkanoate that has been widely studied and used in commercialization.After more than ten years of development,Halomonas bluephageneshas developed into an important platform for the production of PHA.Xylose,the second most abundant sugar in lignocellulosic biomass,cannot be ingested and utilized by wild-type H.bluephagenesis.In this study,through a series of metabolic engineering transformations,Halomonas bluephagenesis successfully used xylose as a carbon source to produce poly-3-hydroxybutyrate.Firstly,this article introduces four different xylose transporters into this strain.The experimental results show that it cannot use xylose for growth,indicating that this strain doesn't contain related genes that can directly metabolize xylose.Furthermore,xylose is introduced on the basis of transporters.After sugar isomerase,the recombinant strain can grow in a medium with xylose as a carbon source.The dry cell weight can reach up to 0.92 g/L,and the PHB yield is 0.39 g/L.On the basis of the above,the xylulose kinase was further introduced to form the xylulose-5-phosphate pathway.In comparison,the dry cell weight decreased to about 0.6 g/L and the PHB output decreased to 0.17 g/L.It proves that xylulose kinase is not suitable for the growth of bacteria and the accumulation of PHB.On the basis of xylose transporter and xylose isomerase,the ribulose-1phosphate pathway was formed by introducing D-tagatose-3-epimerase,Lfucolokinase and L-fuculose-phosphate aldolase.The results showed that the utilization of xylose by the recombinant strains was significantly improved.The dry cell weight reached 2.09 g/L and the PHB yield reached 0.87 g/L.Through the above,the efficient metabolic pathway of xylose in the strain is obtained.The high-yielding PHA strain that cannot use xylose can use xylose to produce PHB.At the same time,this paper proved the role of transporter in H.bluephagenesis and obtained four different types of wood.The difference in the transport efficiency of sugar transporters in this strain.