Gene cloning and characterization of an aldehyde dehydrogenase from long-chain alkane-degrading Geobacillusthermoleovorans B23

Geobacillus thermoleovorans B23 is capable of degrading long-chain alkanes at 70°C. Bt-aldh, an aldehyde dehydrogenase gene in B23, was located in the upstream region of p21 whose expression level was dramatically increased when alkane degradation was started (Kato et al. 2009, BMC Microbiol 9:60). Like p21, transcription level of Bt-aldh was also increased upon alkane degradation. Bt-Aldh (497 aa, MW = 53,886) was overproduced in Escherichia coli, purified, and characterized biochemically. Bt-Aldh acted as an octamer, required NAD+ as a coenzyme, and showed high activity against aliphatic long-chain aldehydes such as tetradecanal. The optimum condition for activity was 50–55°C and pH 10.0. The activity was elevated to two- to threefold in the presence of 2 mM Ba2+, Ca2+, or Sr2+, while Mg2+ and Zn2+ inhibited the enzyme activity. Bt-Aldh represents thermophilic aldehyde dehydrogenases responsible for degradation of long-chain alkanes.