DEVELOPMENT OF METHODOLOGY AND CHARACTERIZATION OF RUMINAL LIPASE-PRODUCING BACTERIA IN VITRO A Thesis by HOLLY

Development of Methodology and Characterization of Ruminal Lipase-Producing Bacteria In Vitro. (May 2011) Holly Danielle Edwards, B.S., Iowa State University Co-Chairs of Advisory Committee: Dr. Rhonda K. Miller Dr. T. Matthew Taylor Hydrolysis of dietary lipids to free fatty acids (FFA) is a prerequisite for ruminal biohydrogenation, a bacterially mediated process that extensively saturates unsaturated FFAs thus limiting the absorption and ultimate assimilation of these healthy nutrients into ruminant produced foods. Three experiments were conducted to learn how to better enrich, isolate and study lipolytic bacteria from the rumen while providing further characterization of four prominent lipase-producing bacteria that are known to be major contributors of lipolysis in the rumen. In experiment one the effects of various physical treatments on ruminal lipase activity were investigated by comparing incubation positions, glass bead levels, transfer techniques and combinations of headspace gasses. Based on results from this experiment an incubation system was established as a standard for subsequent studies for culturing and transferring mixed and pure cultures of ruminal bacteria. In experiment two the effect of glycerol on lipolysis by Anaerovibrio lipolyticus 5S, Butyrivibrio fibrisolvens 49, Propionibacterium avidum, and Propionibacterium acnes was examined. Two levels of glycerol were examined on lipase activity and results showed that glycerol inhibited rates of FFA accumulation at