Two phenoloxidase (PPO) isoforms were purified from Taiwanese black tiger shrimp (Penaeus monodon) purified via ammonium sulfate precipitation and high performance hydrophobic interaction chromatography on phenyl Sepharose CL‐4B. Optimal DL‐ã‐3, 4‐dihydroxyphenylalanine (D, L‐DOPA) oxidation by these isoforms was observed to occur at pH 6.0, and at 45°C. The isoforms showed both mono‐ and di‐PPO activities, and preferential medabolism of both monoand di‐phenolic substrates lacking a carboxyl group either directly attached to the ring, or in the side chain moiety of the phenolic structure.

Aspergillus candidus ATCC 44054 grown without agitation produced more kojic acid in the modified Czapek-Dox liquid medium than cultures shaken at 100 rpm. Of the three culture media tested, yeast extract-sucrose medium permitted more kojic acid production by the fungus than modified Czapek-Dox liquid medium or Tadera medium. Maximal kojic acid (57–59 mg/ml) was produced in the yeast extract-sucrose medium on days 9–12. No aflatoxin by the fungus was detected.