Enantiomerically pure amino acids, amino alcohols, amines, alcohols, and epoxides play an increasingly important role as intermediates in the pharmaceutical industry and agrochemistry, where both a high degree of purity and large quantities of the compounds are required. The chemical industry has primarily relied upon established chemical methods for the synthesis of these intermediates, but is now turning more and more to enzymatic and biotechnological fermentation processes. For the industrial implementation of many transformations alternative methods are available. The advantages of the individual methods will be discussed herein and exemplified by syntheses of relevant compounds.
Enantiomerenreine Aminosäuren, Aminoalkohole, Amine, Alkohole und Epoxide spielen heutzutage als Zwischenprodukte in pharmazeutischer Industrie und Agrochemie eine immer größere Rolle. Dabei sind sowohl ein hoher Reinheitsgrad als auch große Mengen der Verbindungen gefragt. Die chemische Industrie hat sich bei der Synthese dieser Zwischenstufen bislang auf bewährte chemische Verfahren gestützt, greift jedoch zunehmend auf enzymatische und fermentative Prozesse aus der Biotechnologie zurück. Für die industrielle Umsetzung vieler Transformationen stehen alternative Verfahren zur Verfügung. Die Vorteile der einzelnen Methoden werden in diesem Aufsatz anhand der Synthesen wichtiger Beispielverbindungen diskutiert.
A novel L‐pantolactone hydrolase, Lph, from Agrobacterium tumefaciens Lu681 was characterized, which stereospecifically hydrolyses L‐pantolactone to L‐pantoic acid yielding D‐pantolactone with > 95% enantiomeric excess. The enzyme was found to be a 30 kDa‐Zn2+‐hydrolase with a Km for L‐pantolactone of 7 mM and a Vmax of 30 U/mg. The corresponding lph gene was identified as an 807 bp ORF and cloned into E. coli. It was overexpressed under control of Ptac and Prha yielding enzyme activities of up to 600 U/g dry weight. Resolution of d,l‐pantolactone in repeated batches with isolated Lph and enzyme recovery by membrane filtration gave D‐pantolactone with 50% yield and 90–95% ee over 6 days. Covalent immobilization to EupergitC led to a stable biocatalyst easy to handle in a repeated batch production of D‐pantolactone. Further improvements in the activity of Lph were achieved by directed evolution of the enzyme. Activities of mutants F62S, K197D and F100L were increased 2.3, 1.7, and 1.5 fold, respectively.
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