Combined inactivation of the Clostridium cellulolyticum lactate and malate dehydrogenase genes substantially increases ethanol yield from cellulose and switchgrass fermentations

Table 2 Metabolites differing in relative abundance in cell pellets and culture supernatants of Clostridium cellulolyticum mdh, ldh and ldh mdh mutants compared to wild-type at stationary growth phase

Compound	Cell pellets: abundance ratio to wild-type			Culture supernatants: abundance ratio to wild-type
	mdh	ldh	mdh - ldh	mdh	ldh	mdh - ldh
Malic acid	0.32	1.48	0.28	0.84	1.44	0.57
2-Hydroxyglutaric acid	0.28	1.42	12.43	0.35	1.72	4.94
Valine	0.27	1.01	0.37	0.35	1.17	0.68
Glucose-1-P	0.90	1.20	0.56	0.89	1.36	0.57
Fructose-6-P	0.70	0.99	0.79	0.99	2.89	1.39
Glucose-6-P	0.39	1.11	1.12	1.41	9.21	4.69
Succinic acid	0.51	0.56	1.12	0.58	0.92	0.62
Fumaric acid	0.31	0.70	0.40	0.48	0.79	0.36
p-Hydroxybenzoic acid	0.53	0.65	1.24	0.46	0.98	1.77
10.13 191 246 376 348	0.22	0.88	0.25	0.35	1.13	0.90
Citric acid	0.12	0.96	6.03	ND	ND	ND
11.05 191 276	0.44	1.53	0.18	ND	ND	ND
4-Methyl-2-hydroxypentanoic acid	ND	ND	ND	0.17	0.91	2.63
Pyruvic acid	0.56	0.45	0.88	0.18	2.25	0.95
Galactose	ND	ND	ND	3.41	2.67	2.32
2,3-Butanediol	ND	ND	ND	0.29	1.76	1.92
9.97 331 359 226	ND	ND	ND	0.11	1.62	2.12
11.07 191 348 320 246	ND	ND	ND	0.73	1.46	0.44

Metabolites were analyzed by gas chromatography-mass spectrometry (GC-MS) as trimethylsilyl (TMS) derivatives, using a sorbitol internal standard [42]. Peaks that could not be assigned to a standard metabolite are identified by their chromatographic retention times (in min) and their characteristic ion peaks (m/z in italic text).
ND = not determined (the concentrations of these metabolites were too low to produce reliable estimates of relative abundance).

ISSN: 2731-3654