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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).