Thermoanaerobacter

Figure 8.2 Reduction of ketone with alcohol dehydrogenase from Thermoanaerobacter brockii using glucose-6-sulfate as a hydrogen source [3],...

A ruthenium complex [RuCl2(TPPTS)2]2 was used for regeneration of NADP+ to NADPH withhydrogen. Thus, 2-heptanonewas reduced with alcohol dehydrogenase from Thermoanaerobacter brockii in the presence of the mthenium complex, NAD P, and hydrogen at 60°C to (S)-2-heptanol in 40 % ee. Turnover number was reported to be 18 (Figure 8.6) [5cj. 

Reaction temperature is one of the parameters affecting the enantioselectivity of a reaction [16]. For the oxidation of an alcohol, the values of kcat/fQn were determined for the (R)- and (S)-stereodefining enantiomers E is the ratio between them. From the transition state theory, the free energy difference at the transition state between (R) and (S) enantiomers can be calculated from E (Equation 2), and AAG is in turn the function of temperature (Equation 3). The racemic temperature (% ) can be calculated as shown in (Equation 4). Using these equations, % for 2-butanol and 2-pentanol of the Thermoanaerobacter ethanolicus alcohol dehydrogenase were determined to be 26 and 77 °C, respectively. 

FIG. 8 Electron micrographs of freeze-etched preparations of whole cells from (a, b) Bacillus sphaericus CCM 2120 exhibiting a square S-layer lattice or from (c, d) Thermoanaerobacter ther-mohydrosulfuricus Llll-69 carrying a hexagonally ordered S-layer lattice, (a, c) Native S-layer lattices (b, d) S-layer lattices after covalent binding of ferritin to carbodiknide-activated carboxylic acid groups of the S-layer protein. Bars, 100 nm. 

Musa, M.M., Ziegelmann-Fjeld, K.I., Vieille, C. et al. (2007) Asymmetric reduction and oxidation of aromatic ketones and alcohols using W110A secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus. The Journal of Organic Chemistry, 72 (1), 30-34. 

Musa, M., Ziegelman-Fjeld, K., Vieille, C., Zeikus, J. and Phillips, R., Xerogel-encapsulated WHOA secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus performs asymmetric reduction of hydrophobic ketones in organic solvents. Angew. Chem. Int. Ed., 2007, 46, 3091-3094. 

Synecnocystis Chlorobium tepidum Methylococcus capsulatus Rhodobacter capsulatus Rhosdospirillum rubrum Chloroflexus aurantiacus Fibrobacter succinogenes Thermoanaerobacter tengcongensis... 

Bonch-Osmolovskaya EA, Miroshnichenko ML, Chernyh NA, et al. 1997. Reduction of elemental sulfur by moderately thermophilic organotrophic bacteria and description of Thermoanaerobacter sulfurophilus sp. nov. Microbiology 66 483-9. 

Cook GC, Rainey FA, Patel BKC, Morgan HW. 1996. Characterization of a new obligately anaerobic thermophile, Thermoanaerobacter wiegelii sp. nov. Int J Syst Bacteriol 46 123-7. 

The work to be summarized here is preliminary and will be published elsewhere (manuscripts in preparation). Thermoanaerobacter strain B6A produces a xylanase complex diat is inducible by xylose and catabolite repressed by glucose. Noticeably, when mixed with insoluble xylan, glucose-grown cells do not bind xylan whereas, xylose-grown cells bind very tightly. Canonized ferritin was used to identify xylanosome structures in xylose grown cells which are similar to cellulosomes observed in C. thermocellum, Thermoanaerobacter strain B6A produces thermostable cell-bound endoxylanase, which is also excreted. 

The endoxylanase gene from Thermoanaerobacter strain B6A was sequenced and structural interpretations were deduced from computer analysis of the amino acid sequence (see Table VIII). The endoglucanase is hydrophilic and has compact secondary structure with 30 6-tums and five potential glycosylation sites. 

Table VIL Biochemical Properties of Thermoanaerobacter Strain B6A Endoxylanase Cloned in E. coli...

Table Vm. Structural Interpretations Deduced From Amino Acid Sequence Computer Analysis of the Thermoanaerobacter Strain B6A Endoxylanase Gene...

AmylopuUulanase from Thermoanaerobacter Strain B6A. Saha et al. (14) characterized an extraceUular endo-acting amylopuUulanase from Thermoanaerobacter strain B6A which was also isolated from a geothermal site in the USA. The enzyme was produced at high levels on a variety of carbon sources. It was purified to homo-... 

Starch Liquefaction with a Highly Thermostable Cyclodextrin Glycosyl Transferase from Thermoanaerobacter Species... 

Properties of the Thermoanaerobacter sp. CGTase. The CGTase is produced extracellularly at 70 C in a prereduced liquid maltrin medium under argon. The maximal activity level after 40 hours of cultivation is 200 Phadebas units per liter culture broth. 

Pham, V.T., Phillips, R.S. and Ljungdahl, L.G. (1989) Temperature-dependent enantiospecificity of secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus. J. Am. Chem. Soc., 111, 1935-1936. 

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