Effects of CaCl2 on viscosity of culture broth, and on activities of enzymes around the 2-oxoglutarate branch, in Bacillus subtilis CGMCC 2108 producing poly-(γ-glutamic acid)

Bioresour Technol. 2011 Feb;102(3):3595-8. doi: 10.1016/j.biortech.2010.10.073. Epub 2010 Oct 20.

Abstract

CaCl(2) was used as a novel additive to enhance poly-(γ-glutamic acid) (γ-PGA) production by Bacillus subtilis strain CGMCC 2108. Addition of CaCl(2) to medium effectively reduced viscosity of culture broth, and increased consumption of extracellular glutamate by 11.4%, leading to γ-PGA yield of 9.07 g/l, compared to 7.88 g/l in control. CaCl(2) also increased activities of three key enzymes around the crucial 2-oxoglutarate branch of the γ-PGA biosynthesis pathway: isocitrate dehydrogenase (ICDH), glutamate dehydrogenase (GDH), and 2-oxoglutarate dehydrogenase complex (ODHC). In particular, GDH activity was increased more than 8-fold, indicating that more 2-oxoglutarate was directed to synthesis of glutamate, the substrate of γ-PGA. Interestingly, the molecular weight of γ-PGA remained constant regardless of CaCl(2) addition.

MeSH terms

  • Bacillus subtilis / drug effects
  • Bacillus subtilis / metabolism*
  • Calcium Chloride / pharmacology*
  • Culture Media / chemistry*
  • Enzyme Activation / drug effects
  • Ketoglutaric Acids / metabolism*
  • Oxidoreductases / drug effects*
  • Polyglutamic Acid / analogs & derivatives*
  • Polyglutamic Acid / metabolism
  • Viscosity

Substances

  • Culture Media
  • Ketoglutaric Acids
  • poly(gamma-glutamic acid)
  • Polyglutamic Acid
  • Oxidoreductases
  • Calcium Chloride