Plant-based foods, particularly cereals and pseudocereals, are important sources of minerals in the human diet. However, their bioavailability—especially of iron and zinc—is often limited by the presence of antinutritional factors such as phytates, oxalates, polyphenols, and dietary fiber. Among the promising biotechnological approaches to improving the nutritional value of plant-based products, lactic acid fermentation stands out, as microbial enzymes can break down minerals bound in complex compounds, thereby increasing their availability for absorption. In this study, we investigated the effect of lactic acid fermentation on the bioavailability of iron and zinc in three types of flour: wheat, millet, and buckwheat. The substrates were inoculated with three species of lactic acid bacteria (Lactiplantibacillus plantarum, Levilactobacillus brevis and Limosilactobacillus fermentum). The total iron and zinc content in the flours before and after fermentation was determined using inductively coupled plasma mass spectrometry and compared with their bioavailability, measured using the standardized INFOGEST method. Concentrations of phytic acid, oxalic acid, and phosphates were determined by ion-exchange chromatography. The results showed that fermentation with the selected lactic acid bacteria effectively reduced phytate content and increased free phosphate concentration, which may be associated with improved bioavailability of iron and zinc. The most pronounced improvement was observed in millet flour, while the effects in wheat and buckwheat flours were less evident, likely due to grain processing and the presence of other antinutritional compounds. In conclusion, lactic acid fermentation represents an effective and natural approach to enhancing the nutritional value of plant-based flours, with potential for developing functional products with higher contents of bioavailable iron and zinc. However, the effects of this process appear to be highly dependent on the type of substrate, bacterial strain, and target mineral, suggesting that lactic acid fermentation may not be a universal solution to the problem of iron and zinc deficiencies in the diet.
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