Anti-colon cancer and antioxidant activities of bovine skim milk fermented by selected Lactobacillus helveticus strains.

Bioactive compounds released during milk fermentation by proteolytic cleavage of milk proteins have a role beyond their nutritional importance. This study assessed the proteolytic activity of Lactobacillus helveticus strains ASCC953, ASCC474, ASCC1188, and ASCC1315 and their ability to release bioactive compounds capable of exerting antioxidative and in vitro anticarcinogenic properties during incubation at 37°C in reconstituted skim milk. The performance of these strains was not affected by the pH decline during fermentation. Soluble extracts of fermented milk by L. helveticus 474 showed the highest free radical (1,1-diphenyl-2-picrylhydrazyl) scavenging activity at 12 h of fermentation, followed by a significant reduction of this activity at 24 h compared with the other strains and control (untreated milk). Skim milk fermented by L. helveticus strains contained compounds with anti-colon cancer activity at varied levels during fermentation. The activity (19.03-50.98% growth inhibition) was greatest in the extract obtained after 12 h of fermentation, which markedly declined (5.4-9.94%) at the end of fermentation. Lactobacillus helveticus 1315 released compounds into the skim milk supernatant with a greater growth inhibition (50.98%) on colon cancer HT-29 cell line than the other strains. More importantly, these compounds had no significant inhibition effect on normal, primary colon cells T4056. Whereas these results suggest that milk fermented by L. helveticus strains may release bioactive compounds with important multifunctional properties, the characteristics and activities of these compounds appear highly strain- and fermentation time-dependent.