Probable FAD-dependent monooxygenase; part of the gene cluster that mediates the biosynthesis of 5-hydroxy-2-hydroxymethyl-1,4-pyrone, also know as kojic acid, a by-product in the fermentation process of malting rice that acts as a chelation agent (PubMed:20849972). Glucose might be converted to kojic acid by a combination of dehydrogenase and dehydratase reactions involving kojA and probably additional enzymes (PubMed:20849972). Expression is controlled by the kojic acid gene cluster transcription factor kojR (PubMed:21514215). Expression is also positively regulated by the secondary metabolism general regulator laeA (PubMed:21897021). Finally, nitrogen deficiency also positively regulates expression (PubMed:26657710). Leads to the loss of kojic acid production (PubMed:20849972). Kojic acid can be used for several biotechnological applications, including use as an antibiotic, as an additive to prevent browning of food materials, and as an antioxidant (PubMed:17119644). Kojic acid is also interesting as an inhibitor of tyrosinase (PubMed:7714722). Finally, kojic acid has also been shown to have strong nematicidal activity (PubMed:27197670). Belongs to the aromatic-ring hydroxylase family.