Storage stability of crude oxalate oxidase extracted from germinated paddy rice (Oryza sativa L.) and its application in high-oxalate foods

Excessive consumption of soluble oxalate from the diet can elevate the risk of calcium-oxalate kidney stone formation and lead to mineral deficiencies. Reducing dietary oxalate intake is an effective way for lowering urinary oxalate levels. Oxalate oxidase (EC 1.2.3.4), an oxalate-degrading enzyme, has been detected in the germinated paddy rice (Oryza sativa L. IR4625), a staple food in many Asian countries, holds potential as a safe treatment option for individuals suffering from kidney stones and other oxalate-related disorders. This study aimed to assess the storage stability of the crude oxalate oxidase extract isolated from the germinated paddy rice and evaluate its ability to degrade oxalates in high-oxalate foods including spinach, amaranth, cocoa drink, cocoa powder, black tea, and soybean. The crude extracts were stored at 4 °C, 10 °C, and 25 °C for 30 days. By the end of this period, the highest remaining enzyme activity was observed at 4 °C, with an activity loss of approximately 1.4 %. As an enzymatic treatment, oxalate oxidase successfully reduced the oxalate content in the studied food products, with reduction ranging from 9 to 100 % depending on amounts of the enzyme added. This is the first study demonstrating the enzymatic degradation of oxalates in food using plant-derived oxalate oxidase, a crude enzyme extracted from germinated paddy rice (Oryza sativa L. IR4625), offering a non-invasive and chemical-free method of lowering the risk of kidney stones and oxalate-related disorders.