Enhancing the nutritional profile and digestibility of lentil coats by solid state fermentation with selected proteolytic microorganisms.

Background: Lentils are widespread legumes forming basis of a variety gastronomic preparations even thanks to their contribution of proteins and fibres with high biological value. Unlike lentils, their coats (ca. 28%), generated by dehulling and transformation processes are few studied and valorised. Solid state fermentation (SSF) could represent an efficient strategy for the biotransformation and improving the sensory and nutritional profile of lentil coats. This work aimed to develop a biotechnological strategy based on SSF mediated by selected proteolytic microorganisms to increase protein digestibility and the release of bioactive components from lentil coats to be exploited as novel food ingredient. In this work we report the first results of the Next-Generation EU [PNRR] framework “OnFoods” project regarding to the ability to improve the digestibility of proteins in lentil coats, in view of their possible exploitation as a food ingredient. Methods: Lentil coats, obtained by a local shop were finely ground, adjusted initial moisture to 75% (w/w) and autoclavated. Then, they were with different selected strains of fungi, yeast and bacteria endowed of proteolytic activity and belonging to GRAS species. The fermentation was performed for 5 days at 25–30 °C and 90% RH and. Finally, the cultures were homogenized with sterile saline solution for assessing microbial growth. Aliquots of fermented lentils coats were also free-dried and analysed for protein content and electrophoretic profile. Results: Among all the selected strains, only fungi markedly increased the soluble protein content, putatively referred to the biosynthesis of aspartic proteases optimally active at acidic pH such as pepsin. Therefore, next SSF will be conducted with a starter mixture of fungi and lactic acid bacteria evaluating peptide composition and their biological activity. Conclusions: Further evidences are needed to assess the biological activity and safety of peptides from fermented lentil coats by SSF.