Tyrosinase from Agaricus bisporus mushroom waste: isolation, characterization and application on crosslinking casein proteins
Research Poster Health & Life Sciences 2025 Graduate ExhibitionPresentation by Trang Tran
Exhibition Number 162
Abstract
Tyrosinases are copper-containing enzymes that catalyze the oxidation of mono- and di-phenolic compounds, yielding reactive o-quinones. These o-quinones can interact with thiol and amine groups in protein chains, thereby crosslinking and modifying food proteins and enhancing their functional properties such as gelation and film formation. In Pennsylvania, Agaricus bisporus mushroom stumps, an agricultural byproduct posing environmental concerns, represent an untapped, tyrosinase-rich resource. This study investigated the extraction and partial purification of tyrosinase from these stumps. The crude tyrosinase extract exhibited optimal ctivity at pH 7.5 and 45°C, whereas commercial mushroom-derived tyrosinase showed optimal activity at pH 6.5 and 45°C. Electrophoretic analysis showed the enzyme in the crude extract had the same molecular weight as a commercial mushroom tyrosinase (43 kDa). Ammonium sulfate precipitation (30-80% saturation) was employed to partially purify the crude tyrosinase extract, with the highest tyrosinase recovery (47.12%, 4.41 nU/mg) achieved at 50% saturation, followed by the samples from 60% and 70% saturation. Both the crude extract and ammonium sulfate fractions contained proteases, as evidenced by casein digestion in SDS-PAGE analysis. However, the 60-70% ammonium sulfate fraction significantly reduced protease activity while retaining tyrosinase functionality, as demonstrated by the formation of high-molecular-weight protein oligomers from casein, indicative of protein cross-linking activity.
Importance
These results highlight the potential of Agaricus bisporus stumps as a sustainable source of tyrosinase which is now a very expensive enzyme for applications in food protein modification and structure enhancement.