Work

Extraction and use of oxalate oxidase from transgenic American chestnut tree leaves

Year: 2026

Type: article

Abstract: ABSTRACT Background In the 2010s, transgenic Darling 54 (D54) American chestnut trees (ACT) were developed to express an oxalate oxidase (OxO) enzyme that enhances tolerance to oxalate secreted by the chestnut blight fungus. Oxalate is also found in many plant-based foods, including tea, where it contributes to dietary oxalate exposure and kidney stone risk. This study investigated whether transgenic ACT leaves are a potential source of extractable OxO and whether co-brewing ACT leaves with black tea can reduce soluble oxalate content. Methods Fresh D54 ACT leaves were subjected to three extraction conditions. Extracts were purified by ammonium sulfate precipitation and dialysis. OxO activity was quantified using a Trinity Biotech oxalate assay. ACT leaves were co-brewed with six commercial black teas to evaluate effects on soluble oxalate concentration, and different brewing solvents were assessed for their influence on oxalate solubility. Results Extraction at 60°C in 0.1% SDS produced the highest OxO yield (9.74 units/100 g leaves) and demonstrated time-dependent oxalate degradation kinetics. Co-brewing with D54 leaves reduced soluble oxalate concentrations by more than 50% across all six black teas compared with teas brewed alone (p < 0.001). Variation in brewing solvent had minimal impact on oxalate levels, supporting an enzymatic mechanism of oxalate degradation. Conclusions Transgenic D54 ACT leaves provide a functional source of OxO capable of substantially reducing soluble oxalate during tea preparation. These findings demonstrate a potential food-processing strategy for modifying oxalate content in beverages and further support the development of ACT-derived OxO as a functional ingredient for reducing dietary oxalate exposure.

Source: Applied Food Research

DOI: 10.1016/j.afres.2026.102169