Production of ultra-high molecular weight poly-γ-glutamic acid with Bacillus licheniformis P-104 and characterization of its flocculation properties

Appl Biochem Biotechnol. 2013 Jun;170(3):562-72. doi: 10.1007/s12010-013-0214-2. Epub 2013 Apr 4.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus / drug effects
  • Bacillus / genetics
  • Bacillus / metabolism*
  • Calcium Chloride / pharmacology
  • Fermentation
  • Flocculation / drug effects
  • Glycine max / microbiology
  • Hydrogen-Ion Concentration
  • Molecular Weight*
  • Phylogeny
  • Polyglutamic Acid / analogs & derivatives*
  • Polyglutamic Acid / biosynthesis

Substances

  • poly(gamma-glutamic acid)
  • Polyglutamic Acid
  • Calcium Chloride