title: A mathematical model for regulating monomer composition of the microbially synthesized polyhydroxyalkanoate copolymers.
abstract: A mathematical model is proposed for predicting the copolymer composition of the microbially synthesized polyhydroxyalkanoate (PHA) copolymers. Based on the biochemical reactions involved in the precursor formation and polymerization pathways, the model correlates the copolymer composition with the cultivation conditions, the enzyme levels and selectivity, and the metabolic pathways. It suggests the following points: (1) in the case of a sole carbon source, the copolymer composition depends mainly on the topology of the metabolic pathways and the selectivity of both the enzymes involved in the precursor formation and the polymerization route; (2) the copolymer composition can be varied in a wide range via alteration of the flux ratio of different types of monomers channeled from two or more independent and simultaneous pathways; (3) the enzymes which should be over-expressed or inhibited to obtain the desired copolymer composition can be predicted. For example, inhibition of the beta-oxidation pathway will increase the content of the monomer units with longer chain length. To test the model, various experiments were envisaged by varying cultivation time, concentration and chain length of the sole carbon source, and molar ratio of the cosubstrates. The predictions from the model agree well with the experimental results. Therefore, the proposed model will be useful in predicting the PHA copolymer composition under different biochemical reaction conditions. In other words, it can provide a guide for the synthesis of desired PHA copolymers.
authors.affiliation: Institute of Polymer Science and Engineering, Department of Chemical Engineering, School of Material Science and Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.forename: Baohua
authors.initials: B
authors.lastname: Guo
authors.forename: Zengmin
authors.initials: Z
authors.lastname: Zhang
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wu
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhou
authors.forename: Jinchun
authors.initials: J
authors.lastname: Chen
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Chen
authors.forename: Guodong
authors.initials: G
authors.lastname: Li
mesh_terms: D003198:Computer Simulation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008954:Models, Biological; D008956:Models, Chemical; D009097:Multienzyme Complexes / Q000378:metabolism; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry* / Q000378:metabolism*; D044223:Pseudomonas stutzeri / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D000094122:Polyhydroxybutyrates
chemical_list: D009097:Multienzyme Complexes; D011091:Polyesters; D011108:Polymers; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates