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Production of hypoallergenic soy products exhibiting bioactive peptides throughout fermentation technology

Periodic Report Summary 2 - BIOPEPCURE (Production of hypoallergenic soy products exhibiting bioactive peptides throughout fermentation technology)

Food allergy has become a health problem that continues to challenge both the consumer and the food industry. Soybean is included among the most allergenic foods. On the other hand, soy protein is a source of bioactive peptides with health-promoting properties. The aim of this project was to produce hypoallergenic products containing bioactive peptides that help to prevent chronic diseases. Fermentation was used to produce soybean products with low human IgE immunoreactivity. We have also demonstrated that fermentation of soybean meal and its inclusion in diets for newly weaned pigs reduced diarrhea and measures of immunoreactivity in the plasma due to partial digestion of large proteins with antigenic activity (mainly glycinin and beta-conglycinin subunits). Proteases are also used to hydrolyse soybean proteins and reduce soy allergenicity.

On the other hand, anti-inflammatory and antioxidant potential of fermented soymilk was improved using soy indigenous bacterial strains. Moreover, extending fermentation time from 4.5 to 24 h improved the anti-inflammatory properties of fermented soymilk. Although these data warrant further in vivo experiments, the results obtained in the present study suggest the potential use of indigenous soybean strains as starter cultures to produce fermented soymilk that would help to fight against oxidative stress and chronic inflammation which are key factors in the development of several chronic diseases. In this project we also used alcalase from Bacillus licheniformis to obtain soy protein hydrolysates with health-promoting properties. Soy protein hydrolysate produced from alcalase attenuate lipid accumulation through downregulation of gene expression of lipoprotein lipase (LPL) and fatty acid synthase (FAS). Moreover, alcalase soy hydrolysates stimulate expression of anti-inflammatory adipokines (adiponectin) in murine adipocyte cultures and inhibit LPS-induced iNOS / NO and COX-2 / PGE2 pathways in LPS-induced macrophages. An interesting result has been founding that peptides from alpha and alpha subunits of beta-conglycinin are responsible for the effects mentioned above.

Three peptides, KNPQLR, EITPEKNPQLR and RKQEEDEDEEQQRE, were identified as FAS inhibitors blocking the catalytic site of the TE domain of the enzyme which lead to inhibition of lipid accumulation in murine cultured macrophages. Peptide KNPQLR also showed a potent cholesterol lowering activity modulating the expression of enzymes and receptors involved in the synthesis of cholesterol (LDL-R, SREBP2 and HMGCoA reductase) in HEPG2 cells. Peptide KNPQLR also modulates the inflammatory response in LPS-induced macrophages by downregulation of the expression of pro-inflammatory enzymes (iNOS and COX-2). Finally, we conducted a human studies focused on evaluating the health-promoting properties of beta-conglycinin. In a randomised, double-blind, placebo controlled study we demonstrated that consumption of beta-conglycinin enriched soymilk (LGS) by overweight men reduced oxidised LDL, increased plasma adiponectin and also contributed to body composition maintenance. LGS may be a useful product to include in meals designed to improve the health of overweight individuals.