Effect of calcium and sodium salts on ethanol production in high sugar fermentation by free cells ofZymomonas mobilis

Summary Addition of calcium carbonate enhanced ethanol production byZymomonas mobilis ZM4 and a mutant (ZMI₂), especially at higher concentrations (200–400 g/L) of glucose and sucrose, as well as at higher temperature (42°C) by the mutant. Calcium and sodium carbonates neutralized the acid produced in the medium and enhanced the ethanol production. The Na salts were less effective in the parent strain and were not favourable for the mutant. Ca²⁺ ions played a direct role in augmenting ethanol production as evidenced by the effect of calcium chloride at controlled pH (5.5).