title: Production of ultra-high molecular weight poly-γ-glutamic acid with Bacillus licheniformis P-104 and characterization of its flocculation properties.
abstract: A novel strain of Bacillus licheniformis P-104 was isolated from Chinese soybean paste to produce a bioflocculant. The bioflocculant was confirmed as ultra-high molecular weight poly-γ-glutamic acid (γ-PGA) using Fourier transform infrared spectrum, high-performance liquid chromatography, and gel permeation chromatography with multi-angle laser light scattering. The production technology and flocculation properties of γ-PGA were investigated. By fed-batch fermentation in a 7-L bioreactor, the maximum γ-PGA yield reached 41.6 g L(-1) with a productivity rate of 1.07 g L(-1) h(-1). The flocculating activity of γ-PGA for kaolin suspension was 33.5±1.6 1/OD under the optimized flocculation conditions (6 mM Ca(2+), 1.5 mg L(-1) γ-PGA, and pH 6.0). The optimized dosage of γ-PGA for flocculation was just about 30 % of that of reported γ-PGA produced by other strains. Moreover, the flocculation activity of γ-PGA produced by strain P-104 was much higher than commercial γ-PGA with the molecular weight ranging 200-500 kDa and 1,500-2,500 kDa. This study provided a promising strain and an efficient method for production of ultra-high molecular weight γ-PGA which could be used as a potential green bioflocculant.
authors.affiliation: College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Caifeng
authors.initials: C
authors.lastname: Zhao
authors.forename: Yewei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xuetuan
authors.initials: X
authors.lastname: Wei
authors.forename: Zhongbo
authors.initials: Z
authors.lastname: Hu
authors.forename: Feiyan
authors.initials: F
authors.lastname: Zhu
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.forename: Mingfang
authors.initials: M
authors.lastname: Luo
authors.forename: Huizhou
authors.initials: H
authors.lastname: Liu
mesh_terms: D001407:Bacillus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D005285:Fermentation; D005427:Flocculation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010802:Phylogeny; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis; D013025:Glycine max / Q000382:microbiology
chemical_list: C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D002122:Calcium Chloride