CaCl2 was used as a novel additive to enhance poly-(c-glutamic acid) (c-PGA) production by Bacillus subtilis strain CGMCC 2108. Addition of CaCl2 to medium effectively reduced viscosity of culture broth, and
increased consumption of extracellular glutamate by 11.4%, leading to c-PGA yield of 9.07 g/l, compared
to 7.88 g/l in control. CaCl2 also increased activities of three key enzymes around the crucial 2-oxoglutarate branch of the c-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 c-PGA. Interestingly, the molecular weight of c-PGA remained constant regardless of
CaCl2 addition.