Browning of acetate medium by Herellea vaginicola (Achromobacter anitratus)

A brown coloration developed in the culture filtrate when Herellea vaginicola (Achromobacter anitratus) grew profusely in a sodium acetate and ammonium dihydrogen phosphate basal salts liquid medium. Variations of environmental and cultural conditions affected the intensity of the brown color. The conditions studied were temperature, 25° and 37°, duration of incubation, aeration of growing cultures, and various concentrations of the nitrogen and carbon source. Spectrophotometric and solubility studies suggest that the observed brown coloration was not due to a bacterial pigment. Chromatographic analyses of freeze-dried culture fluid after acid hydrolysis showed six amino acids, one amino hexose, and two hexoses. A Maillard reaction occurring among the components in the supernatant appears to be responsible for the observed brown color.