Effect of ammonium and amino acids on the growth of selected strains of Gluconobacter and Acetobacter

Acetic acid bacteria (AAB) are a group of microorganisms highly used in the food industry. However, its use can be limited by the insufficient information known about the nutritional requirements of AAB for optimal growth. The aim of this work was to study the effects of different concentrations and sources of nitrogen on the growth of selected AAB strains and to establish which nitrogen source best encouraged their growth. Two strains of three species of AAB, Gluconobacter japonicus, Gluconobacter oxydans and Acetobacter malorum, were grown in three different media with diverse nitrogen concentrations (25, 50, 100, and 300 mg N/L and 1 g N/L) as a complete solution of amino acids and ammonium. With this experiment, the most favourable medium and the lowest nitrogen concentration beneficial for the growth of each strain was selected. Subsequently, under these conditions, single amino acids or ammonium were added to media individually to determine the best nitrogen sources for each AAB strain. The results showed that nitrogen requirements are highly dependent on the nitrogen source, the medium and the AAB strain. Gluconobacter strains were able to grow in the lowest nitrogen concentration tested (25 mg N/L); however, one of the G. oxydans strains and both A. malorum strains required a higher concentration of nitrogen (100-300 mg N/L) for optimal growth. In general, single nitrogen sources were not able to support the growth of these AAB strains as well as the complete solution of amino acids and ammonium.