Skip to main content

Table 3 Effect of resazurin (Res) and Neutral Red (NR) on fermentation of switchgrass (SWG) by mixed ruminal microflora in vitro

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

Variable Resazurin (Res, in mM) without Neutral Red (NR) 0.5 mM NR SEDa P > F,
Resb
P > F,
NRc
No Res Res (0.008) Res (0.03) Res (0.10) Res (0.25) Res (0.45) No Res Res (0.008)
SWG digested(mg) 74.9 A 75.2 A 73.3 AB 72.2 AB 73.3 AB 70.9 AB 66.7 ABC 64.3 BC 2.39 0.597 0.967
Net μmol
 H2 0.13 B 0.14 B 0.10 B 0.25 B 0.27 B 0.09 B 2.23 A 2.42 B 0.29 0.154 0.999
 Methane 110.0 A 109.6 A 108.4 A 107.3 A 107.7 A 106.1 A 37.6 B 35.2 B 3.72 0.932 0.997
 Formate 0 B 1.3 B 0 B 0 B 0 B 0 B 23.7 A 18.1 A 4.0 0.785 0.846
 Acetate 359.1 A 339.0 A 338.2 A 336.7 A 337.4 A 300.0 A 222.7 B 208.5 B 18.3 0.176 0.990
 Propionate 140.1 148.2 137.5 143.8 144.7 138.4 160.5 153.7 7.44 0.714 0.976
 Butyrate 30.4 26.2 27.7 25.9 26.9 25.7 30.4 27.9 3.50 0.573 0.995
 Isobutyrate 1.3 AB 2.1 A 1.7 A 0.9 AB 1.5 AB 1.0 AB 0 0 1.43 0.314 1.000
 Valerate 4.0 AB 2.0B 2.5 B 2.2 B 2.2 B 2.2 B 5.6 A 5.5 A 0.78 0.227 1.000
 Isovalerate + 2 MB 4.7 2.6 4.4 2.2 3.3 2.4 0 0 1.4 0.585 1.000
 Caproate 0.31 0.38 0 0 0 0 0 0 0.14 0.113 1.000
 Total C2–C6 VFA 534.1 A 520.5 A 512.1 A 511.6 A 516.0 A 469.9 AB 416.7 B 391.3 B 25.6 0.277 0.953
 Total VFA alkyld 752.0 A 741.0 A 729.8 A 722.1 A 733.7 A 675.6 AB 647.3 B 604.5 B 33.0 0.313 0.867
 Total alkyle 861.8 AB 850.6 AB 838.2 AB 829.4 AB 841.5 AB 781.7 AB 684.9 BC 639.7 C 34.1 0.294 0.854
 ACLf 2.41 B 2.42 B 2.43 B 2.41 A 2.42 A 2.44 B 2.55 A 2.55 A 0.024 0.454 0.997
μmol H (mg SWG)−1 41.31 39.44 39.94 40.14 39.97 38.30 34.48 35.34 1.88 0.806 0.965
Combustion, kJ (g SWG digested)−1 9.94 9.51 9.65 9.67 9.65 9.26 8.65 8.46 0.83 0.832 0.608
  1. Values are least-square means from triplicate cultures that contained 190 mg switchgrass (DM basis), 2.0 mL diluted ruminal inoculum and 10 mL total liquid volume. End product amounts from 72 h fermentations have been corrected for inoculated blank vials that lacked SWG.
  2. aPooled standard error of the difference.
  3. bComparison of least-square means across all treatments not containing NR (0–0.45 mM resazurin).
  4. cComparison of least-square means between NR and NR + 0.008 mM resazurin.
  5. dSum of methyl plus methylene groups in C2–C6 VFA.
  6. eIncludes methane.
  7. fAverage chain length of VFA (excluding formate).
  8. ABC different letters within row indicate differences in least-square means (P < 0.05).