Effect of nitrogen supply, Zn2+, and salt concentration on kojic acid and versicolorin biosynthesis byAspergillus parasiticus

We have compared the effects of variation of culture conditions on the biosynthesis of kojic acid and versicolorin A byAspergillus parasiticus (ATCC 36537). Under permissive conditions, both of these secondary metabolites appear in the culture between 40 and 50 h after conidial inoculation. Kojic acid synthesis is maximal with 0.2% peptone and is depressed by additional peptone or ammonia, with 1% peptone or 50 mM NH4+ almost completely eliminating synthesis. These concentrations of nitrogen source cause a much smaller depression of versicolorin synthesis. Versicolorin production is completely dependent on Zn2+ whereas kojic acid synthesis is unaffected by changes in the concentration of Zn2+ or Fe3+. Certain salts inhibit production of both kojic acid and versicolorin, with nearly complete inhibition by 0.8M NaCl or by 0.05M NaOAc.