title: Solubility and thermal response of fractionated cyanophycin prepared with recombinant Escherichia coli.
abstract: Cyanophycin, also known as cyanophycin granule polypeptide (CGP), is a non-ribosomal polypeptide consisting of aspartic acid as a backbone with arginine and lysine as the side chains. CGP has soluble (sCGP) and insoluble (iCGP) forms based on its aqueous solubility. In order to investigate the role of lysine in its physical properties, CGP was prepared with recombinant Escherichia coli cultivated at different temperatures, and the purified sCGP and iCGP were further fractionated with different ethanol concentrations and pHs, respectively. Low temperature cultivation was found to favor the production of more sCGP. The ratio of iCGP/sCGP increased from 0.12 to 0.35 when the cultivation temperature being raised from 17 to 37°C. After fractionation the same fraction of either sCGP or iCGP contained an approximate content of lysine, and therefore showed expectantly similar physical properties, irrespective of the cultivation temperatures. A high arginine/lysine ratio was found to result in low solubility and high molecular weight. Fractions of sCGP showed upper critical solution temperatures (UCST) below 5°C in phosphate buffered saline whereas iCGP exhibited a UCST around 28-31°C at pH 3. The particle size of iCGP was around 300-500nm as revealed by transmission electron microscopy. The thermal responses of CGP present a potential in biomedical applications, such as drug delivery.
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan. Electronic address: tsengwc@mail.ntust.edu.tw.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Tseng
authors.affiliation: Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan. Electronic address: tyfang@mail.ntou.edu.tw.
authors.forename: Tsuei-Yun
authors.initials: TY
authors.lastname: Fang
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
authors.forename: Yuan-Chieh
authors.initials: YC
authors.lastname: Hsieh
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
authors.forename: Chien-Yu
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
authors.forename: Meng-Che
authors.initials: MC
authors.lastname: Li
mesh_terms: D001120:Arginine / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D008239:Lysine / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012995:Solubility; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; C024250:cyanophycin; D001120:Arginine; D008239:Lysine
keywords: Biopolymer; Cyanophycin; Polypeptide; Upper critical solution temperature (UCST)