Effect of glycerol and dihydroxyacetone concentrations in the culture medium on the growth of acetic acid bacteria Gluconobacter oxydans ATCC 621

Abstract

Bacteria of the species Gluconobacter oxydans are applied in the industrial production of dihydroxyacetone (DHA) via glycerol oxidation. The major problem of this biotransformation involves process inhibition by substrate and/or product. Improper initial concentration of glycerol and increasing DHA concentration may inhibit the metabolic activity of bacterial cells and impede further course of the reaction. An attempt was, therefore, undertaken in this study to determine which concentrations of glycerol (30, 50, 70, 100 g L -1 ) and DHA (10-100 g L -1 ) may inhibit the growth of acetic acid bacteria of G. oxydans ATCC 621 species. Cultures of this strain were run in the Bioscreen C MBR apparatus on experimental culture media with various initial concentrations of glycerol and DHA. Analyses were also carried out to examine the impact of pH (5.0, 7.0, 8.0) of glycerol-containing culture media on cell growth of the analyzed strain G. oxydans. None of the applied substrate concentrations was inhibiting cellular divisions of G. oxydans bacteria. The initial glycerol concentrations that enabled rapid cellular divisions reached 50 g L -1 in the medium with pH 5.0 (coefficient of specific growth rate μ = 0.0550) and 70 g L -1 in the medium with pH 7.0 (μ = 0.0556). DHA was shown to inhibit the mitotic activity of G. oxydans bacteria even at low concentrations (20-30 g L -1 ), whereas at the concentration of 70 g L -1 , it made cell divisions impossible. The applied pH values of the culture media did not inhibit the growth of G. oxydans strain. © 2014 The Author(s).