Relevance. Whole grain products are becoming increasingly popular in industrialized countries due to their high content of dietary fiber, vitamins, and minerals. Soaking wheat grain is a crucial stage in the production of whole grain bread. To improve the quality and health benefits of whole grain bread, enzyme preparations based on cellulase are used during the grain soaking stage. This biotechnological technique influences the localization and content of key biologically active substances in the grain. New knowledge about the redistribution of chemical compounds within wheat grain during enzymatic hydrolysis will help develop guidelines for optimizing the soaking process.Methods. The study presents experimental data on the effect of a complex enzyme preparation based on cellulase and sodium selenite, introduced during wheat grain soaking, on changes in the microstructure of the main morphological parts of the grain, antioxidant activity, the content of chemical compounds determining antioxidant activity, and the distribution of mineral elements within the grain kernel.Results. Soaking Nadir wheat grain in a buffered solution of an enzyme preparation based on cellulase and sodium selenite for 10 hours under optimal conditions for enzyme action results in a modification of the microstructure of the grain’s morphological parts. Antioxidant activity increases by 9.3% (DPPH radical inhibition), total flavonoid content (by 0.05%), anthocyanin content (by 0.132%), and glutathione content (by 12 mg%) compared to the grain soaked in water. Biologically active mineral elements and selenium accumulate in the germ after grain fermentation.