# Tyrosinase Recovered from White Button Mushroom Waste: Extraction, Characterization, and Application in Casein Cross-Linking

## TL;DR

Researchers extracted tyrosinase from mushroom waste to use it for cross-linking proteins, offering a cost-effective way to repurpose agricultural byproducts.

## Contribution

The study introduces a novel method to recover and characterize tyrosinase from white button mushroom stumps for protein modification.

## Key findings

- Tyrosinase was successfully recovered from white button mushroom stumps and showed optimal activity at pH 7.5 and 45 °C.
- Ammonium sulfate fractionation improved purification and activity recovery of the enzyme.
- Partial purification and use of EDTA/PMSF enabled effective casein cross-linking despite protease interference.

## Abstract

Tyrosinase catalyzes the oxidation of mono- and diphenols
to o-quinones, which can polymerize and covalently
cross-link
proteins, but the limited availability and high cost of purified tyrosinase
limit broader use. This study recovered tyrosinase from white button
mushroom (Agaricus Bisporus) stumps,
an underutilized byproduct, and evaluated it for food protein modification.
Proteomics identified multiple tyrosinase isozymes (AbPPO3, AbPPO4,
AbPPO5), and the crude tyrosinase exhibited optimal activity at pH
7.5 and 45 °C, with a prominent 43 kDa protein band. Ammonium
sulfate fractionation (50–70% saturation) increased specific
activity; the 50% fraction achieved 4.4-fold purification with 47%
activity recovery. Effects of chemical modulators, metal ions, salts,
reductants, chelators, and inhibitors were systematically assessed.
Endogenous proteolysis hindered cross-linking, but partial purification
and EDTA/PMSF suppressed protease activity, enabling tyrosinase-catalyzed
casein polymerization. These results demonstrate a cost-effective
source to valorize mushroom waste into a tyrosinase biocatalyst for
protein cross-linking.