Alcohol dehydrogenases AdhE and AdhB with broad substrate ranges are important enzymes for organic acid reduction in Thermoanaerobacter sp. strain X514

Table 1 Purification of the major NADH-dependent alcohol dehydrogenase AdhE of Thermoanaerobacter sp. strain X514. NADH-dependent ADH activity was measured in 50 mM Tris buffer (pH 7.5) supplemented with 2 mM DTE and 4 µM resazurin as NADH (0.5 mM)-dependent reduction of acetaldehyde (10 mM) at 65 °C

Purification step	Total protein [mg]	Specific activity [U mg⁻¹]	Total activity [U]	Yield [%]	Purification [fold]
Cell-free extract	1423	1.2	1734	100.0	1.0
Cytoplasm	1196	1.8	2183	125.9	1.5
Q-Sepharose	877	2.7	2323	134.0	2.2
(NH₄)₂SO₄ precipitation	511	4.7	2413	139.2	3.9
Phenyl-Sepharose	220	7.3	1602	92.4	6.0
Superose 6	2.8	61.2	173	9.9	50.2

The decrease in absorption of NADH was followed at 340 nm. One unit represents one µmol of acetaldehyde reduced per minute. The major ALDH activity (CoA and NAD⁺-dependent oxidation of acetaldehyde) co-purified due to the bifunctionality of AdhE (Additional file 1: Table S1)

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