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Table 2 Effect of tannic acid (TA) on in vitro switchgrass (SWG) fermentations by mixed ruminal microorganisms

From: Redox mediators modify end product distribution in biomass fermentations by mixed ruminal microbes in vitro

Variable Least-square mean valuesa SEDb Model P > F
Control (no TA) 0.1 g TA L−1 0.3 g TA L−1 1.0 g TA L−1
SWG digested (mg DM) 79.3 A 79.8 A 76.9 A 70.0 B 2.2 0.007
mmol product (g SWG consumed)−1
 Methane 1.29 A 1.40 A 1.19 AB 1.02 B 0.079 0.015
 Acetate 5.14 5.42 5.17 5.31 0.906 0.906
 Propionate 2.10 A 2.22 A 1.95 AB 1.58 B 0.154 0.015
 Butyrate 0.342 0.420 0.345 0.334 0.052 0.370
 Valerate 0.008 0.011 0.032 0 0.015 0.246
 Caproate 0.013 0.018 0.014 0.014 0.003 0.197
 BCVFAc 0.022 0.050 0.014 0.002 0.017 0.104
 Total VFA 7.62 8.13 7.52 7.13 0.68 0.568
 Total VFA-C 18.17 19.59 17.89 16.78 1.317 0.430
 Total alkyl in SCFAd 10.54 11.40 10.33 9.12 1.057 0.267
ACLe 2.38 A 2.40 A 2.37 A 2.27 B 0.024 0.024
Final pH 6.41 6.41 6.39 6.42 0.051 0.940
Enthalpy of combustion, kJ (g SWG digested)−1 9.74 10.51 9.52 8.77 0.827 0.287
  1. Vials contained 190 mg switchgrass DM and 2.0 mL of diluted mixed ruminal inoculum in a total liquid volume of 10 mL.
  2. aValues are from triplicate cultures after 72 h incubation, after correction for inoculated blank vials lacking SWG. Values within row having different letters (A, B) differ (P < 0.05).
  3. bPooled standard error of the difference.
  4. cBranch-chain C4–C5 VFA (sum of isobutyrate, 2-methylbutyrate, and isovalerate).
  5. dSum of methyl and methylene groups in VFA.
  6. eAverage chain length of VFA.