Methods of Phytic Acid Reduction in Bitter Lupine Seeds and Their Effects on the Microbiota of Calves

Phytic acid is an antinutritional factor present in lupine seeds, which limits the bioavailability of essential minerals such as calcium, iron, and zinc. This study evaluated different methods of reducing phytic acid in bitter lupine (Lupinus angustifolius) and investigated the effects of the resulting reduction in phytic acid on the composition of gut microbiota. Bitter lupine is a legume rich in protein and fiber, but its high phytic acid content can limit mineral bioavailability. Four processing methods were compared as follows: thermal treatment, enzymatic hydrolysis with phytase, spontaneous fermentation, and controlled fermentation using lactic acid bacteria. Controlled fermentation resulted in the highest phytic acid reduction (96.37%), significantly improving mineral availability. Simulated digestion revealed that the fermented lupine feed positively influenced gut microbiota, increasing Lactobacillus abundance. Enzymatic and thermal treatments preserved more protein. However, they were less effective at removing phytic acid. These findings highlight controlled fermentation as a promising strategy for improving the nutritional value of lupine-based feed, offering a sustainable alternative to soybean-based livestock diets.