In nature, living organisms are constantly producing different macromolecules for their metabolic needs. These macromolecules, such as polysaccharides, polynucleotides, proteins, or polyesters, are essential to organism survival. Their synthesis generally involves in vivo enzyme-catalyzed chaingrowth polymerization reactions of activated monomers, which are generally formed within the cells by complex metabolic processes. Because of their diversity and renewability, microbial polymers such as polysaccharides, bacterial polyhydroxyalkanoates (1) and polyanions such as poly(γ-glutamic acid) (2) have received increasing attention as candidates for industrial applications. In many cases, microorganisms carry out polymer syntheses that are impractical or impossible to accomplish with conventional chemistry. Thus, microbial catalysts enable the production of materials that might otherwise be unavailable. Microbial polymers are synthesized from renewable low-cost feedstocks, and the polymerizations operate under mild process conditions with minimal environmental impact. In addition, microbial polymers provide products that, when disposed, can degrade to nontoxic products.

https://homepages.rpi.edu/~grossr/_doc/publication/Chem.%20Rev.%202001,%20101,%202097-2124.pdf

Polymer Synthesis by In Vitro Enzyme Catalysis

Recent advances in supramolecular coordination chemistry have allowed chemists to synthesize macromolecular complexes that exhibit various properties intrinsic to enzymes. This Review focuses on structures inspired by properties and functions observed in enzymes rather than precise models of enzyme active sites. These structures are synthesized using convergent, modular, and high-yielding coordination-chemistry-based methods, which allow one to tailor the size, shape, and properties of the resulting complexes. Many of the structures discussed exhibit reactivity and specificity reminiscent of natural systems, and some of them have functions that exceed the natural systems which provided the inspiration for initially making them.

Enzyme Mimics Based Upon Supramolecular Coordination Chemistry

Galacto-oligosaccharides (GOS) have now been definitely established as prebiotic ingredients after in vitro and animal and human in vivo studies. Currently, GOS are produced by glycoside hydrolases (GH) using lactose as substrate. Converting lactose into GOS by GH results in mixtures containing GOS of different degrees of polymerization (DP), unreacted lactose, and monomeric sugars (glucose and galactose). Recent and future developments in the production of GOS aim at delivering purer and more efficient mixtures. To produce high-GOS-content mixtures, GH should not only have good ability to catalyze the transgalactosylation reaction relative to hydrolysis, but also have low affinity for the GOS formed relative to the affinity for lactose. In this article, several microbial GH, proposed for the synthesis of GOS, are hierarchized according to the referred performance indicators. In addition, strategies for process improvement are discussed. Besides the differences in purity of GOS mixtures, differences in the position of the glycosidic linkages occur, because different enzymes have different regiochemical selectivity. Depending on oligosaccharide composition, GOS products will vary in terms of prebiotic activity, as well as other physiological effects. This review focuses on GOS production from synthesis to purification processes. Physicochemical characteristics, physiological effects, and applications of these prebiotic ingredients are summarized. Regulatory aspects of GOS-containing food products are also highlighted with emphasis on the current process of health claims evaluation in Europe.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1541-4337.2010.00119.x

Galacto‐Oligosaccharides: Production, Properties, Applications, and Significance as Prebiotics

Purine nucleoside phosphorylases: properties, functions, and clinical aspects.

Synthesis of complex carbohydrates and glycoconjugates: enzyme-based and programmable one-pot strategies.

Enzymes hold great potential for asymmetric synthesis of polyhydroxy species and their chiral intermediates. This article describes recent progress in the area, including the syntheses of monosacharides, polysaccharides, nucleosides and their analogs, derivatives, conjugates, or intermediates based on combined chemical-enzymatic reactions. Highly regio- and stereoselective reactions in aqueous solutions or organic solvents with minimim protection and deprotection are demonstrated.

Thomas Krach

Papers

Enzyme Catalysis in Synthetic Carbohydrate Chemistry

Probing the acceptor specificity of .beta.-1,4-galactosyltransferase for the development of enzymatic synthesis of novel oligosaccharides

Synthesis of novel disaccharides based on glycosyltransferases: β1,4galactosyltransferase

Enzyme Catalysis in Synthetic Carbohydrate Chemistry

Probing the Acceptor Specificity of β-1,4-Galactosyltransferase for the Development of Enzymatic Synthesis of Novel Oligosaccharides.