Kojic acid is a valuable compound that contributes to various therapeutic and cosmetic applications. Organic nitrogen partially

contributes to fermentation and mostly prefers cell growth as well as increases production costs. This study aims to

fi nd the eff ect of low-cost inorganic nitrogen in the form of ammonium chloride on kojic acid production from fungal isolate

Aspergillus sp. BU20S. A 3.63-times increase in the kojic acid (4.43 ± 0.47 g/L) was found when only the ammonium chloride

was supplemented in glucose (10 g/L) medium than other minimal salts. The product formation was 2.52 ± 0.56 g/L in

ammonium chloride as compared to 2.02 ± 0.06 g/L yeast extract after 10 days. The carbon/nitrogen ratio (C/N) was found

optimal as 15 (molecular C/N: 23.58) which gives a high titer of 5.17 ± 0.84 g/L from 10 g/L of glucose. At this optimal

molecular nitrogen value, the nitrogen supplement cost can be reduced by 93–99% compared to yeast extract. The antimicrobial

potential of kojic acid purifi ed from the fermented broth was also studied against methicillin-resistant Staphylococcus

aureus (MRSA). The purifi ed kojic acid showed a ~ 20 mm zone of inhibition at a 2.5 mg dose loaded over 7.4 × 10 9 CFU/

mL of MRSA. This study concludes that only ammonium chloride is a suffi cient inorganic nitrogen source to produce kojic

acid and is useful in reducing production costs. The purifi ed kojic acid is also an eff ective antimicrobial agent.