Expression of a heat-stable NADPH-dependent alcohol dehydrogenase in Caldicellulosiruptor bescii results in furan aldehyde detoxification

Table 2 Mass balance of 15 mM furfural or 15 mM 5-HMF containing C. bescii batch fermentations

	Concentrations (mM)							Carbon Recovery (%)^a	Concentrations (mM)		O/R^d
	Cellobiose consumed	Glucose	Acetate	Lactate	CO₂	Biomass	H₂	Carbon Recovery (%)^a	Furfuryl alcohol^b	5-HMF alcohol^c	O/R^d
15 mM Furfural
JWCB001	6.5 ± 0.6	7.2 ± 0.6	7.3 ± 0.6	3.4 ± 0.3	7.7 ± 0.5	0.4 ± 0.0	12.9 ± 0.9	98.51	3.6 ± 0.8		0.90
JWCB018	5.3 ± 0.3	4.6 ± 0.3	10.5 ± 0.6	ND	10.8 ± 0.8	0.4 ± 0.1	15.5 ± 1.2	95.40	3.2 ± 06		1.11
JWCB044	6.7 ± 0.4	6.0 ± 0.4	14.6 ± 1.0	ND	15.0 ± 0.7	0.5 ± 0.0	18.7 ± 0.7	102.82	13.1 ± 0.6		0.92
15 mM 5-HMF
JWCB001	10.1 ± 0.5	7.3 ± 0.5	14.4 ± 0.5	9.8 ± 0.9	15.6 ± 0.4	1.2 ± 0.1	24.5 ± 2.5	100.95		3.4 ± 0.4	1.03
JWCB018	9.5 ± 0.3	6.7 ± 0.6	17.8 ± 1.2	ND	18.8 ± 1.5	1.2 ± 0.1	31.9 ± 1.8	87.39		3.9 ± 0.7	1.01
JWCB044	10.1 ± 0.2	7.7 ± 0.7	18.2 ± 1.5	ND	19.4 ± 0.4	1.2 ± 0.2	30.9 ± 1.9	87.57		13.6 ± 0.0	0.84

Metabolite concentrations were determined at the end of 72 h batch fermentations.
ND not detected.
^aCarbon recovery is the ratio of carbon compounds produced divided by the carbon compounds consumed and is expressed as a percentage.
^bFurfuryl alcohol was not reliably quantifiable via HPLC analyses. Values represent the reduction in furfural from the culture medium and assume 100% reduction to furfuryl alcohol.
^cAmount of 5-HMF removed from the culture medium was 3.8 ± 0.5 mM (JWCB001), 4.5 ± 0.7 mM (JWCB018) and 14.9 ± 0.0 mM (JWCB044).
^dRatio of oxidized end-products to reduced end-products.

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