The lipases from Thermomyces lanuginosus (immobilized by granulation with silica) and Candida antarctica B (adsorbed on Lewatit, "Novozym 435") were comparatively assayed for the synthesis of sugar esters by transesterification of sugars with fatty acid vinyl esters in 2-methyl-2-butanol:dimethylsulfoxide mixtures. We found that lipase from C. antarctica B is particularly useful for the preparation of 6,6'-diacylsucrose, whereas T. lanuginosus lipase catalyzes selectively the synthesis of 6-Oacylsucrose. The granulated T. lanuginosus lipase retained more than 80% of its initial activity after 20 cyles of 6 hours. Both lipases were similarly effective for the regioselective synthesis of 6'-O-palmitoylmaltose and 6-O-lauroylglucose. The effect of the synthesized sugar esters on the growth in liquid medium of various microorganisms (Gram-positive, Gram-negative and yeasts) was evaluated. 6-Olauroylsucrose and 6'-O-lauroylmaltose inhibited the growth of Bacillus sp. at a concentration of 0.8 mg/ml, and of Lactobacillus plantarum at 4 mg/ml. Sucrose dilaurates and 6-O-lauroylglucose did not show antimicrobial activity, probably due to their low aqueous solubility. As regards the inhibition of yeasts, none of the tested carbohydrate esters inhibited significantly the growth of Zygosaccharomyces rouxii and Pichia jadinii.

A metagenome expression library of bulk DNA extracted from the rumen content of a dairy cow was established in a phage lambda vector and activity-based screening employed to explore the functional diversity of the microbial flora. Twenty-two clones specifying distinct hydrolytic activities (12 esterases, nine endo-beta-1,4-glucanases and one cyclodextrinase) were identified in the library and characterized. Sequence analysis of the retrieved enzymes revealed that eight (36%) were entirely new and formed deep-branched phylogenetic lineages with no close relatives among known ester- and glycosyl-hydrolases. Bioinformatic analyses of the hydrolase gene sequences, and the sequences and contexts of neighbouring genes, suggested tentative phylogenetic assignments of the rumen organisms producing the retrieved enzymes. The phylogenetic novelty of the hydrolases suggests that some of them may have potential for new applications in biocatalysis.

The selective extraction of capsaicinoids and carotenoids from chili guajillo "puya" flour was studied. When ethanol was used as solvent, 80% of capsaicinoids and 73% of carotenoids were extracted, representing an interesting alternative for the substitution of hexane in industrial processes. Additionally, when the flour was pretreated with enzymes that break the cell wall and then dried, extraction in ethanol increased to 11 and 7% for carotenoid and capsaicinoid, respectively. A selective two-stage extraction process after the treatment with enzymes is proposed. The first step uses 30% (v/v) ethanol and releases up to 60% of the initial capsaicinoids, and the second extraction step with industrial ethanol permits the recovery of 83% of carotenoids present in the flour.

We describe for the first time the enzymatic acylation of the phenolic group of tocopherols (vitamin E) by transesterification with vinyl acetate in 2-methyl-2-butanol (2M2B). Out of 15 hydrolases screened, only the lipase B from Candida antarctica (Novozym 435) catalyzed the acylation. The acetylation of -tocopherol was faster than that of -tocopherol, probably due to its lower methylation degree. A series of experiments using (R)-Trolox and p-cresol as competitive acceptors of tocopherols showed that reaction rate notably diminished when increasing acceptor size. To maximize the potential of this reaction, three immobilization carriers for C. antarctica lipase B were studied: the ion-exchange resin Lewatit (the support in Novozym 435), a biodegradable polymer (Purasorb) and polypropylene (Accurel EP100). The acetylation of -tocopherol was faster with the enzyme immobilized in polypropylene, which was correlated with its higher porosity. A mixture hexane/2M2B 90:10 (v/v) was found to be the optimum medium composition, as it represents a compromise between substrates solubility and biocatalyst efficiency. The acylation process was no enantioselective, probably due to the fact that the chiral centers are separated from the phenolic group by a minimum of six bonds.

No abstract