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

AMB Express

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

Variable	Least-square mean values^a				SED^b	Model P > F
Variable	Control (no TA)	0.1 g TA L⁻¹	0.3 g TA L⁻¹	1.0 g TA L⁻¹	SED^b	Model P > F
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
BCVFA^c	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 SCFA^d	10.54	11.40	10.33	9.12	1.057	0.267
ACL^e	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

Vials contained 190 mg switchgrass DM and 2.0 mL of diluted mixed ruminal inoculum in a total liquid volume of 10 mL.
^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).
^bPooled standard error of the difference.
^cBranch-chain C₄–C₅ VFA (sum of isobutyrate, 2-methylbutyrate, and isovalerate).
^dSum of methyl and methylene groups in VFA.
^eAverage chain length of VFA.