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Responses of Rumen Microbes to Excess Carbohydrate

Hackmann, Timothy John
http://rave.ohiolink.edu/etdc/view?acc_num=osu1364922613

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Nutrition Program, The Ohio State University.
Some species of rumen microbes respond to excess carbohydrate by synthesizing reserve carbohydrate, but others respond by spilling energy (producing heat alone). The response of mixed cultures of species, however, has not been directly studied, and elucidating the response was the focus of the present research. The first aim was to evaluate methods for detecting reserve carbohydrate, in an attempt to find one that was quantitative. Methods compared were those based on the (i) anthrone reaction and (ii) hydrolysis with amyloglucosidase. Compared to the amyloglucosidase hydrolysis method, the anthrone method detected a larger increase (P = 0.017) in cell carbohydrate when glucose (20 mM) was dosed in cultures. Additionally, it detected a larger decrease (P = 0.049) in cell carbohydrate after glucose was exhausted. This result indicated that the anthrone method detected more carbohydrate that functions as a reserve material. For the anthrone method, recoveries for energy (97.5%), carbon (100.2%), and cell components (99.8%) were high, indicating carbohydrate was completely detected. For the amyloglucosidase hydrolysis method, recoveries were lower. The anthrone method appeared to accurately quantify changes in reserve carbohydrate and shows merit for quantitative studies. The second aim was to determine if a mixed rumen microbes would respond to excess carbohydrate by accumulating reserve carbohydrate, spilling energy, or both. Mixed microbes from the rumen were washed with N-free buffer and dosed with glucose. Total heat production was measured by calorimetry. Energy spilling was calculated as heat production not accounted by (i) endogenous metabolism and (ii) synthesis of reserve carbohydrate. For cells dosed with 5 mM glucose, synthesis of reserve carbohydrate and endogenous metabolism explained nearly all heat production (93.7%); no spilling was detected (P = 0.226). For cells dosed with 20 mM glucose, energy spilling was not detected immediately after dosing, but it became significant (P < 0.05) approximately 30 min after dosing glucose. Energy spilling accounted for as much as 38.7% of heat production in one incubation. As documented for some pure cultures, mixed microbial communities from the rumen can respond to large excesses of carbohydrate by spilling energy. The third aim was to determine how Gibbs energy (ΔG)&#x2014;a thermodynamic property of reactions—was impacted by the specified physical state of gases. The second experiment (above) required calculation of thermodynamic properties, but it was found different authors specify different states for gases for these calculations. Our analysis indicated the aqueous, not gaseous, state is that used by microbes and should be the one specified in calculations. Compilation of literature values showed that microbial reactions create disequilibrium between aqueous and gaseous concentrations of gases, and the pattern of disequilibrium suggests the aqueous state is used. The greater the disequilibrium, the greater ΔG was impacted (up to 60.50 kJ/mol) when changing from the gaseous to the aqueous state. Because ΔG was so impacted, our results suggest that aqueous gas concentrations must be measured to accurately estimate ΔG. By establishing appropriate calculations for ΔG, our results should advance understanding of microbial processes where energetics play a key role.
Jeffrey Firkins, Ph.D. (Advisor)
Daniel Bond, Ph.D. (Committee Member)
Thaddeus Ezeji, Ph.D. (Committee Member)
Gonul Kaletunc, Ph.D. (Committee Member)
William Weiss, Ph.D. (Committee Member)
125 p.
Agriculture; Animal Sciences; Applied Mathematics; Biochemistry; Biostatistics; Energy; Experiments; Livestock; Microbiology; Nutrition
rumen; microbiology; animal nutrition; energy spilling; reserve carbohydrate; glycogen; cow; glucose

Recommended Citations

Citations

  • Hackmann, T. J. (2013). Responses of Rumen Microbes to Excess Carbohydrate [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364922613

    APA Style (7th edition)

  • Hackmann, Timothy. Responses of Rumen Microbes to Excess Carbohydrate. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1364922613.

    MLA Style (8th edition)

  • Hackmann, Timothy. "Responses of Rumen Microbes to Excess Carbohydrate." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364922613

    Chicago Manual of Style (17th edition)

osu1364922613
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© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.