title: Physicochemical properties of cross-linked poly-gamma-glutamic acid and its flocculating activity against kaolin suspension.
abstract: Cross-linked poly-gamma-glutamic acid (C-L gamma-PGA) was prepared with gamma-PGA irradiated with gamma-ray at various kGy values. The physicochemical properties including viscosity and water absorption capacity were compared between C-L gamma-PGA and several typical flocculating agents. The viscosity of C-L gamma-PGA increased with the dose of gamma-irradiation, although the water absorption capacity of C-L gamma-PGA did not, which showed a maximum of 1005.6 ml/g at 20 kGy. Flocculating activity against kaolin suspension was not observed for any of the test compounds when used singly. However, the activity of C-L gamma-PGA markedly increased following the addition of polyaluminum chloride. The activity increased with temperature up to 80 degrees C and remained at 80 degrees C of heat pretreatment for 1 h, but did not at more than 50 degrees C of heat pretreatment for 24 h. The activity was also observed within a pH range of 4.5-10.0. Both the water absorption capacity and flocculating activity of C-L gamma-PGA decreased in parallel with increasing NaCl concentration, suggesting that the flocculating activity of C-L gamma-PGA was associated with its water absorption capacity, rather than viscosity. An investigation of the effects of various cations on the flocculating activity of C-L gamma-PGA showed that only trivalent cations had a synergistic effect. The mechanism of C-L gamma-PGA flocculating activity is discussed based on the results of preliminary experiments.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka City University, Osaka, Japan. makoto@sci.osaka-cu.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Kouji
authors.initials: K
authors.lastname: Kato
authors.forename: Ayako
authors.initials: A
authors.lastname: Shimauchi
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Fujita
authors.forename: Toshio
authors.initials: T
authors.lastname: Tanaka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tarui
authors.forename: Eiji
authors.initials: E
authors.lastname: Hirasawa
mesh_terms: D000327:Adsorption; D001407:Bacillus / Q000378:metabolism*; D003102:Colloids / Q000032:analysis / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry*; D011099:Polyglutamic Acid / Q000737:chemistry*; D012996:Solutions; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D003102:Colloids; D003432:Cross-Linking Reagents; D012996:Solutions; D014867:Water; D007616:Kaolin; D011099:Polyglutamic Acid