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Title:   Author  item
                                            EDWARDS, HOLLY - Texas A&M Universityitem
                                            Anderson, Robinitem
                                            TAYLOR, T - Texas A&M Universityitem
                                            MILLER, RHONDA - Texas A&M Universityitem
                                            HARDIN, MARGARET - Texas A&M Universityitem
                                            Nisbet, Daviditem
                                            KRUEGER, NATHAN - Blinn Collegeitem
                                            SMITH, STEPHEN - Texas A&M University
  Submitted to: Lipids
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 3/5/2013
                                    Publication  Date: 4/23/2013
                                    Citation: Edwards, H.D., Anderson, R.C., Taylor, T.M., Miller, R.K., Hardin, M.D., Nisbet, D.J., Krueger, N.A., Smith, S.B. 2013. Interactions between oil substrates and glucose on pure cultures of ruminal lipase-producing bacteria. Lipids. 48:749-755.Interpretive Summary: Medium and long chain fatty acids produced from the breakdown of fats in the gastrointestinal tract can affect the diversity and function of the resident microbial population.  For instance, some long chain fatty acids such as oleic, linoleic, and linolenic acid can directly exhibit antimicrobial activity against some microbes or can act indirectly by inactivating multidrug efflux pumps expressed by some antimicrobial-resistant bacteria thereby making them more susceptible to antibiotics.  In order to further characterize the ability of four prominent fat-metabolizing gut bacteria to break down fats, we measured their growth and fat-metabolizing ability when provided oleic acid-rich olive oil, linoleic acid-rich corn oil, or linolenic acid-rich flaxseed oil as their main food source either when present with or without added glucose.  Results from our studies revealed considerable variability in lipolytic activity between the different bacteria, with rates of lipolysis for all oil sources being considerably higher with P. avidum than the other tested bacteria.  Results further revealed that corn oil was more resistant to being metabolized than olive or flaxseed oil by Propionibacterium avidum as well as by Anaerovibrio lipolyticus and Butyrivibrio fibrisolvens but appeared to be readily metabolized by Propionibacterium acnes.  The rate of growth by Propionibacterium avidum was unaffected by glucose or by oil source.  Conversely, the rates of growth by the other fat-metabolizing bacteria, Anaerovibrio lipolyticus, Butyrivibrio fibrisolvens, and Propionibacterium acnes, were increased in the presence of glucose and affected by the different oil substrates, with corn oil generally supporting less rapid rates of growth than olive or flaxseed oil.  These results clearly show that fat metabolism by prominent fat-metabolizing bacteria can be differentially affected by glucose or different oil sources and suggests that corn oil, being resistant to breakdown by some prominent fat-metabolizing bacteria, may be the least inhibitory against pathogenic bacteria.  This research provides new knowledge about how different dietary constituents can affect the microbial population in the gut of food-producing animals and may ultimately lead to new strategies to help farmers and ranchers produce microbiologically safe foods for the American consumer.
                                Technical Abstract: The hydrolysis of free fatty acids from lipids is a prerequisite for biohydrogenation, a process that effectively saturates free fatty acids.  Anaerovibrio lipolyticus and Butyrivibrio fibrisolvens have long been thought to be the major contributors to ruminal lipolysis; however, Propionibacterium avidum and acnes have been identified recently as contributing esterase activity in the rumen.  In order to further characterize the lipase activity of these bacterial populations, each was grown with three different lipid substrates, olive oil, corn oil, and flaxseed oil.  In addition, different finishing rations contain varying levels of glycogen (a source of free glucose).  Thus, this study was repeated in the presence and absence of glucose to determine its influence on lipolysis.  Propionibacterium avidum and A. lipolyticus demonstrated the most rapid rates (P < 0.05) of lipolysis for cultures grown with olive oil and flaxseed oil, respectively.  Corn oil displayed substantial resistance to the lipolytic activity of A. lipolyticus, whereas flaxseed oil and olive oil were readily hydrolyzed by these ruminal bacteria.  Thus, glucose differentially regulates growth and lipolysis activity of prominent rumen lipid metabolizing bacteria.


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