Production of B-group vitamins by two Azotobacter strains with phenolic compounds as sole carbon source under diazotrophic and adiazotrophic conditions.

Azotobacter vinelandii strain ATCC 12837 and A. chroococcum strain H23 (CECT 4435) were able to grow on N-free or NH4Cl-amended chemically-defined (Burk's) media, with protocatechuic acid (1-2 mmol 1(-1)) or sodium p-hydroxybenzoate (1-10 mmol 1(-1)) as sole carbon (C) sources. At a concentration of 2 mmol 1(-1), both substrates supported nitrogen fixation (acetylene reduction assay) at similar or higher rates than bacteria grown in control media amended with 2 mmol 1(-1) sodium succinate as C source. The two strains produced the B-group vitamins niacin, pantothenic acid, thiamine, riboflavin and biotin after 72 h of growth in chemically-defined media with 2 mmol 1(-1) protocatechuic acid, sodium phydroxybenzoate or sodium succinate as sole C source, either in N-free media or in media amended with 0.1% NH4Cl. Quantitative production of all vitamins was affected by the use of the different C and N substrates.