Production of prebiotic oligosaccharides and antihypertensive peptides by Kluyveromyces from dairy origin

Abstract

Yeast products have been used for many years as ingredients and additives in food processing. Nowadays bioactive compounds produced by yeasts present new challenges for the food industry. Yeast ß-galactosidase activity, traditionally used to produce low-lactose products and for the biological treatment of cheese whey waste, is gaining importance due to the production of prebiotic oligosaccharides by means of transgalactosylation reactions. Also proteolytic enzymes, traditionally relevant to the development of flavour and texture of dairy products, are receiving increasing attention for their potential to release bioactive peptides from milk proteins. We have isolated Kluyveromyces lactis and K. marxianus from cheese and selected those with ß-galactosidase and caseinolytic activity. The selected strains were able to produce oligosaccharides derived from lactulose (OsLU) and casein-derived peptides with antihypertensive effect. With respect to OsLu production the Kluyveromyces strains produced 6-galactobiose, 6α-galactosyl-lactulose, 1-galactosyl-lactulose and unknown oligosaccharides in the reaction mixtures. Formation of trisaccharides predominated over other oligosaccharides. K. marxianus strain O3 produced the highest yields of OsLu after 4h reaching values of 45% corresponding to 87% of lactulose hydrolysis. The ability to release antihypertensive casein-derived peptides was tested on microbiological medium with casein as sole nitrogen source. The inhibitory effects of casein hydrolysates on angiotensin I-converting enzyme (ACE) activity were determined. The best hydrolysates were selected and permeate fractions with molecular masses lower than 3 kDa were obtained. When orally administered to spontaneously hypertensive rats, the permeates exerted in vivo antihypertensive effect. In conclusion, the present study contributes to a better insight into bioactive compounds produced by dairy yeasts. It shows the feasibility of ß-galactosidases to transglycosylate lactulose producing high yields of prebiotics oligosaccharides and the potential of selected yeasts to produce orally effective antihypertensive casein-derived hydrolysates.