Biocatalysts thermophilic

When looking for a suitable biocatalyst, one has also to consider the (operational) activity that is required for commercial application and the operational conditions that will be used in the process (e.g. temperature, salt concentration, pH, organic solvents, substrate and product concentration) will have to be addressed as well. If the reaction is optimally performed at for instance high temperatures, thermophilic organisms are more likely to provide the desired enzymes than mesophilic strains (see paragraph 5.4.1). And vice versa, /isychrophiles operate well at lower temperatures and, since they do not require excessive heat treatment to be inactivated, are easily killed following the process. 

Perhaps the acid-tolerant, thermophilic Bacillus coagulans is the only known biocatalyst that naturally produces lactic acid from xylose via the pentose phosphate pathway, not the phosphoketolase pathway (Patel et al., 2006). Three strains, 17C5, P4-102B, and 36D1, can ferment both hexoses and pentoses to pure L(+)-lactic acid at 50 °C and pFI 5.0, an optimal environment... 

It is clear that recombinant DNA technology has had a major impact on commercial production of L-aspartic acid. With the exception of a thermophilic process, there would appear little need for further development of a better enzyme, as the currently available biocatalysts are extremely cost efficient [44,45]. Future development will be aimed at L-aspartic acid processes that produce less waste and use cheaper starting materials. Current L-aspartic acid processes require bromine as the catalyst for the isomerization of maleic acid to fumaric acid, while... 

Thermoplasma acid philum 1.70 Thermophile, suffur- oxidizer/biomining, biocatalysts... 

Beadle BM, Baase WA, Wilson DB et al. (1999) Comparing the thermodynamic stabilities of a related thermophilic and mesophilic enzyme. Biochemistry 38(8) 2570-2576 Blumenthal DK, StuU JT (1982) Effects of pH, ionic strength and temperature on activation by calmodulin and catalytic activity of myosin light chain kinase. Biochemistry 21 2386-2391 Bommarius AS, Broering JM (2005) Established and novel tools to investigate biocatalyst stabUity. Biocatal Biotransform 23(3/4) 125-139... 

Another advantage of extremely thermophilic enzymes is that when they are produced recombinantly in mesophilic hosts, heat treatment serves as an efficient method to purify the target enzyme from the host s proteins, which readily denature at higher temperatures (21). This strategy can be used to great advantage for biocatalyst production. 

The availability of genome sequence data has created the possibility of identifying an extremely thermophilic counterpart to almost any mesophilic enzyme or protein with industrial potential. Thus, robust replacement biocatalysts can be considered for a range of current enzyme applications. Of course, new biocataljdic processes that advantageously utilize high temperature enzymes are of considerable interest. Discussed below are several examples of such cases. 

For example, a ferredoxin hydrogenase (EC 1.12.7.2) has been isolated recently from the hyperthermophile Pyrococcus fUriosus [38]. The performance of this biocatalyst, which showed a remarkable stability under operative conditions, has been investigated for the NADPH regeneration in the reduction of prochiral ketones catalyzed by the thermophilic NADPH-dependent ADH from Thermoanaerohium sp. Total turnover numbers (TTNs mole product/mole consumed cofactor NADP" ") of 100 and 160 could be estimated in the reduction of acetophenone and (2S)-hydroxy-l-phenyl-propanone, respectively. As a side note, it should be mentioned that, although the activity of the P. furiosus hydrogenase increased exponentially with temperature up to its maximum above 80 °C, the reactions had to be performed at much lower temperature (40 °C) because of the thermal instability of NADPH. 

During the last decades, several NOXs have been purified from various microbial strains belonging to the genera Streptococcus [50-52], Lactobacillus [49, 53, 54], Methanocaldococcus [55], Brevibacterium [56], Eubacterium [57], Thermococcus [48, 58-60], Archaeo bus [61], and Clostridium [62]. In particular, NOXs purified from thermophilic microorganisms are of interest because they are very stable biocatalysts, which enable biotransformations to be operated at high temperature and at increased reaction rates [48]. 

B Sonnleitner, H Grueninger, R Laforce, U Baier, A Fiechter. Production and Application of Thermophilic Biocatalysts, 3rd European Congress of Biotechnology, 1984, Vol I, pp 1—29. 

Blumer-Schuette SE, Kataeva I, Westpheling J, Adams MWW, Kelly RM (2008) Extremely thermophilic microorganisms for biomass conversion status and prospects. Curr Opin Biotechnol 19 210-217 Bode HB, Bethe B, Hofs R, Zeeck A (2002) Big effects from small changes possible way to explore nature s chemical diversity. Chembiochem 3 619-627 Bommarius AS, Blum JK, Abrahamson MJ (2011) Status of protein engineering for biocatalysts how to design an industrially useful biocatalyst. Curr Opin Chem Biol 15 194-200... 

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