Suchergebnisse

Amino acids are of paramount importance as chiral building blocks of life, for drug development in modern medicinal chemistry, and for the manufacture of industrial products. In this work, the stereoselective synthesis of (S)- and (R)-2-amino-4-hydroxybutanoic acid was accomplished using a systems biocatalysis approach comprising a biocatalytic one-pot cyclic cascade by coupling of an aldol reaction with an ensuing stereoselective transamination. A class II pyruvate aldolase from E. coli, expressed as a soluble fusion protein, in tandem with either an S- or R-selective, pyridoxal phosphate dependent transaminase was used as a catalyst to realize the conversion, with formaldehyde and alanine being the sole starting materials. Interestingly, the class II pyruvate aldolase was found to tolerate formaldehyde concentrations of up to 1.4 M. The cascade system was found to reach product concentrations for (S)- or (R)-2-amino-4-hydroxybutanoic acid of at least 0.4 M, rendering yields between 86% and >95%, respectively, productivities of >80 g L–1 d–1, and ee values of >99%. ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 635595 (CarbaZymes), the Ministerio de Economía y Competitividad (MINECO), the Fondo Europeo de Desarrollo Regional (FEDER) (grant no. CTQ2015-63563-R to P.C.), and COST action CM1303 Systems Biocatalysis. ; We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed

The objective of this study was to determine the energy values, standardized ileal digestibility coefficients and digestible amino acid contents of parboiled brown rice bran (PBRB), protein sorghum meal (PSM) and bread waste meal (BWM) in broiler diets. In the first trial, 144 broiler chicks at 14 days of age were evaluated in a completely randomized design involving three feedstuffs + a control diet, with six replicates and six birds per experimental unit. The total excreta collection method was adopted to determine the energy values of the feedstuffs. In the second trial, 144 broilers at 24 days of age were used in a completely randomized design involving three feedstuffs + a protein-free diet, with six replicates and six birds per experimental unit. Ileal digesta was harvested to determine the standardized ileal digestibility coefficients and digestible amino acid contents of the feedstuffs. The nitrogen-corrected apparent metabolizable energy (AMEn) values of PBRB, PSM and BWM were 2638, 2799 and 3399 kcal.kg-1, respectively. The metabolizability coefficients of AMEn (CAMEn) of PBRB, PSM and BWM were 54.13, 57.35 and 86.66%, respectively. Bread waste meal had the highest CAMEn (p < 0.05) and standardized ileal digestibility of amino acids (p < 0.01), followed by PBRB and PSM. The main limiting digestible amino acids in PBRB, PSM and BWM were found at the following respective levels: methionine - 0.19, 0.33 and 0.24%; lysine - 0.40, 0.46 and 0.40%; threonine - 0.25, 0.50 and 0.45%; and valine - 0.44, 0.73 and 0.48%.