Enzymatic characterization, surface display, and application of Dichomitus squalens oxalate decarboxylase to enhance nutritional quality of wheat germ.

High oxalate content in feed can exacerbate bone calcium loss, leading to osteoporosis and paralysis. However, no specialized method currently exists for degrading oxalate in feed. This study aimed to develop an effective oxalate degradation strategy using probiotic-enzyme synergy, characterize the novel D. squalens oxalate decarboxylase (DsOxdC), and validate the nutritional improvement of treated feed materials. We present an effective method to degrade oxalate in feed materials through synergistic fermentation of probiotics and oxalate decarboxylase. The soluble expression of DsOxdC was systematically studied. Purified DsOxdC efficiently degrades oxalate at pH 5.0 and 50 °C, demonstrating superior catalytic efficiency with the highest specific activity of 4.43 μmol/(min·mg), kcat of 1476 s-1, Km of 3.74 μM, and kcat/Km of 395.0 s-1·μM-1, respectively. Surface display engineering enhanced its pH and thermal resistance. Molecular dynamics simulations revealed that the DsOxdC-oxalate complex stability correlates with its high random coil content, explaining the enzyme's exceptional oxalate specificity. Synergistic fermentation reduced wheat germ oxalate content by 34 % while improving palatability and nutritional value (e.g., increased the content of soluble sugar, GABA, and glutathione by 32 %, 200 %, and 56 %). This study establishes a novel, practical approach for antinutritional factor mitigation in animal feed.