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 l−1) or sodium p‐hydroxybenzoate (1–10 mmol l−1) as sole carbon (C) sources. At a concentration of 2 mmol l−1, both substrates supported nitrogen fixation (acetylene reduction assay) at similar or higher rates than bacteria grown in control media amended with 2 mmol l−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 l−1 protocatechuic acid, sodium p‐hydroxybenzoate 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.

Azotobacter vinelandii strain ATCC 12837 and Azotobacter chroococcum strain H23 (CECT4435) were tested to grow in N-free or NH(4)Cl amended chemically defined media, with protocatechuic acid or sodium p-hydroxybenzoate as sole carbon (C) sources at a concentration of 2 mmol/L. Both substrates supported grow at similar rates than bacteria grown in control media amended with 2 mmol/L sodium succinate as C source. The two strains produced aspartic acid, serine, glutamic acid, glycine, hystidine, threonine, arginine, alanine, proline, cysteine, tyrosine, valine, methionine, lysine, isoleucine, leucine and phenylalanine after 72 h of growth in chemically defined media with 2 mmol/L of phenolic compounds or sodium succinate as sole C source amended or unamended with 0.1% (w/v) NH(4)Cl. Qualitative and quantitative production of all amino acids was not affected by the use of different C and N substrates.