Biocatalysis emerged as a key technology in the chemical and pharmaceutical industries, creating demands for enzymes with novel functions. These enzymes have to be available at low cost, most often requiring recombinant protein production. The engineered whole-cell biocatalysts producing the protein of interest are evaluated in dependence of the amount of functional enzyme produced.The focus of this thesis was on the optimization and characterization of recombinant beta-aminopeptidase production as novel catalysts for L-carnosine synthesis in aqueous solution. The bacterium Pseudomonas putida and the two yeasts Saccharomyces cerevisiae and Pichia pastoris were engineered for efficient recombinant beta-aminopeptidase production, while using a previously reported Escherichia coli based expression system as reference. The engineered strains performed extraordinary in industrial-like fed-batch fermentations, with titers of up to 6.5 g L -1 target protein using P. pastoris. The novelty of the P. pastoris fermentation regards the protein synthesis rate that was increased considerably by exchanging the state of the art carbon substrate methanol with glucose.