Lactobacillus kefir cells

Biphasic systems that include ionic liquids can also be applied to whole-cell biocatalysis. The ability of these solvents to act as a substrate reservoir and in situ extracting agent was demonstrated by an efficient asymmetric ketone reduction. 4-Chloroacetophenone was reduced to the key pharmaceutical intermediated (k)-l-(4-chlorophenyl) ethanol using Lactobacillus kefir cells in ILs. The indigenous cellular cofactor regeneration system remained active, which allowed high product concentrations without cofactor supplementation [34]. 

Similarly, whole-cell Lactobacillus kefir DSM 20587, which possesses two alcohol dehydrogenases for both asymmetric reduction steps, was applied in the reduction of tert-butyl 6-chloro-3,5-dioxohexanoate for asymmetric synthesis of ft rf-butyl-(31 ,5S)-6-chloro-dihydroxyhexanoate (Figure 7.5), a chiral building block for the HMG-CoA reductase inhibitor [ 17]. A final product concentration of 120 him and a specific product capacity of 2.4 mmol per gram dry cell were achieved in an optimized fed-batch process. Ado 99% was obtained for (3R,5S)- and (3.S, 55)-te/ f-butyl-6-chloro-dihydroxyhexanoate with the space-time yield being 4.7 mmolL-1 h-1. 

Figure 7.5 Reduction of tert-butyl 6-chloro-3,5-dioxohexanoate by whole-cell Lactobacillus kefir DSM 20587...

Lactobacillus kefir was also employed as the whole-cell biocatalyst for the asymmetric reduction of ethyl 4-chloroacetoacetate to ethyl (.S )-4-chloro-3-hydroxybutanoate, the chiral... 

An example of a whole-cell process is the two-step synthesis of an enantiopure epoxide by asymmetric reduction of an a-chloro ketone (Scheme 6.4), catalyzed by recombinant whole cells of an Escherichia coli sp. overexpressing an (R)-KRED from Lactobacillus kefir and GDH from Thermoplasma acidophilum, to the corresponding chlorohydrin, followed by non-enzymatic base-catalyzed ring closure to the epoxide [17]. 

Lactobacillus brevis whole-cell biotransformation When the reduction of diketo ester la was performed with whole cells of Lactobacillus brevis or L. kefir, formation of the 3,5-dihydroxy ester (3R,5S)-5a was observed [10, 22]. This was surprising since it is known that the prevailing alcohol dehydrogenase in I. brevis is the one described as LBADH [23] and since, moreover, this enzyme does not reduce P-keto 5-hydroxy ester 2a to the corresponding dihydroxy ester (Scheme 2.2.7.6). Under the conditions tested, further alcohol dehydrogenase activity is clearly present in I. brevis and I. kefir. Pfruender et al. optimized the production of L. kefir cells and used this biocatalyst for the one-pot synthesis of dihydroxy ester syn-(3R,5S)-5a using diketo ester la as starting material [24]. 

Since cinnamyl aldehyde is the main component of cassia oil (approximately 90%) and Sri Lanka cinnamon bark oil (approximately 75%) [49], it is industrially more important to generate cinnamyl alcohol, which is less abundantly available from nature but is important as cinnamon flavour, by biotransformation of natural cinnamyl aldehyde than vice versa. Recently, a whole-cell reduction of cinnamyl aldehyde with a conversion yield of 98% at very high precursor concentrations of up to 166 g L was described [136]. Escherichia coli DSM 14459 expressing a NADPH-dependent R alcohol dehydrogenase from Lactobacillus kefir and a glucose dehydrogenase from Thermoplasma acidophilum for intracellular cofactor regeneration was applied as the biocatalyst (Scheme 23.8). 

Fig. 40 Concept for the two-step synthesis of enantiomerically pure (S)-epoxides out of aliphatic 1-halogenated 2-ketones. The ketone was reduced by a recombinant whole-cell catalyst bearing alcohol dehydrogenase from Lactobacillus kefir (LKADH) and glucose dehydrogenase (GDH) for regeneration of NADPH. Base-induced cyclization of the enantiomerically pure (5)-(3-halohydrin intermediate gave the desired (S)-epoxides in high yield and enantiomeric purity (>99% ee)...

An example of glucose coupled ketone reduction is the continuous mode reduction using whole (dead) cells of Lactobacillus kefir for the enantioselective reduction of 2,5-hexanedione to (2R,5R)-hexanediol - a popular chiral ligand for... 

Lb. reuteri is a member of the consortium of bacteria involved in kefir production (Heller, 2001). Amongst 58 strains of Lactobacillus species isolated from kefir, approximately 19% of the isolates showed the ability to bind to Caco-2 cells by competitive binding with Salmonella typhimurium (Santos, San Mauro, Sanchez, Torres, Marquina, 2003). This area still remains unexplored for determining whether EPS, known to be secreted by some of these strains, is indeed the causative agent Lactobacillus plantarum is not often associated with fermented dairy products, but it has been isolated as one of the major species from a traditional milk of the Maasai (Mathara et al., 2008) Lb. plantarum (strain LP6) was determined to bind to rat intestinal mucus... 

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