THE BINDING AND DEGRADATION OF NISIN BY MIXED RUMINAL BACTERIA

Authors: LEE, S - CORNELL UNIVERSITY; MANTOVANI, H - CORNELL UNIVERSITY; Russell, James

Submitted to: Federation of European Microbiological Societies Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2002
Publication Date: 8/3/2002
Citation: LEE, S., MANTOVANI, H.C., RUSSELL, J.B. 2002. THE BINDING AND DEGRADATION OF NISIN BY MIXED RUMINAL BACTERIA. FEDERATION OF EUROPEAN MICROBIOLOGICAL SOCIETIES MICROBIOLOGY ECOLOGY. 42:339-345.

Interpretive Summary: Cattle in the U.S. are often fed antibiotics, but the widespread use of antibiotics in animal feed has been criticized. Antibiotics are primarily targeted against gram-positive gut bacteria. Gram-positive ruminal bacteria produce large amounts of hydrogen a precursor of methane, as well as ammonia which is a wasteful end-product of amino acid degradation. These bacteria also produce lactic acid which causes ruminal acidosis, ruminal ulcers, founder and even death of the animal. Some bacteria produce peptides (bacteriocins) that can inhibit gram-positive bacteria, and bacteriocins have been proposed as an alternative to antibiotics. In this paper, we show that the bacteriocin, nisin, can be degraded by ruminal bacteria, but this degradation did not prevent its ability to act in inhibiting mixed ruminal bacteria. Research on bacteriocins has the potential to decrease the need for antibiotic in animal feed.

Technical Abstract: Nisin catalyzed potassium efflux from glycolyzing S. bovis cell suspensions, and the steady state concentration of residual potassium was dependent on the amount of nisin added. The relationship between nisin concentration and potassium depletion was a saturation function that had considerable cooperativity. By pre-incubating mixed ruminal bacteria with nisin and removing them prior to S. bovis JB1 addition, it was possible to estimate the ability of mixed ruminal bacteria to bind or degrade nisin. Low concentrations of mixed ruminal bacteria did not bind or degrade all of the nisin in 6 h, but little nisin remained if the mixed ruminal bacteria were present at more than 50 ug protein per ml. Because cell-free ruminal fluid (10% v/v) inactivated the nisin in less than 2 h, and this inactive could be counteracted by autoclaving, ultra-filtration and proteinase inhibitor it appeared that there was an enzymatic degradation of nisin. Mixed ruminal bacteria degraded nisin rapidly, but this degradation did not prevent potassium depletion from mixed ruminal bacteria. These latter results indicated that nisin binding was faster than nisin degradation. The idea that nisin binding could protect nisin from degradation was supported by the observation that intact nisin could be extracted from mixed ruminal bacteria. These observations support the hypothesis that bacteriocins can be used to modify ruminal fermentation, but further work will be needed to see if these peptides can be produced economically.