Isolation and characterization of tyrosinase inhibitor-producing microorganisms from marine environment

Abstract

Tyrosinase inhibitor-producing microorganisms were isolated from the marine environment and characterized. Out of about 500 isolates from various sea areas, only three strains that were isolated from sediment samples of Off-Izu Islands and Sagami Bay were found to produce the inhibitors. Among the three, strain H1-7 that was isolated from Off-Izu Islands had significantly and constantly the strongest inhibitory activity (1000-2500 U/mL) and was selected for further studies on the identification of the strain and production of the inhibitor. The strain showed abundant to moderate growth covered with aerial mycelium on most media except for Miura's medium and cornmeal agar, forming a white sparse mycelial mat at first and later a conidial area shaded yellowish white to greenish yellowish gray. The diameter of the aerial mycelium without seawater was much larger than the medium with seawater on all the media tested. It had antimicrobial activity against most microbes tested. Based on the taxonomical characteristics, strain H1-7 belonged to the genus Trichoderma and was named Trichoderma sp. H1-7. The optimal medium for the production of the inhibitor was investigated by using shake flasks and an improved basal medium. The maximum production of the inhibitor was observed in a medium consisting of 2% soluble starch, 1% glucose, 0.5% Bacto-peptone (Difco) and 0.5% Bacto-yeast extract (Difco) at pH 7.5 in 50% (v/v) seawater for 2 days with shaking.