Biocatalysis has found numerous applications in various fields as an alternative to chemical catalysis. The use of enzymes in organic synthesis, especially to make chiral compounds for pharmaceuticals as well for the flavors and fragrance industry, are the most prominent examples. In addition, biocatalysts are used on a large scale to make specialty and even bulk chemicals. This review intends to give illustrative examples in this field with a special focus on scalable chemical production using enzymes. It also discusses the opportunities and limitations of enzymatic syntheses using distinct examples and provides an outlook on emerging enzyme classes.

/pdf/biocatalysis-enzymatic-synthesis-for-industrial-applications-ldqm2uv3af.pdf

Biocatalysis: Enzymatic Synthesis for Industrial Applications

Oligosaccharides, compounds that are composed of 2 – 10 monosaccharide residues, are major carbohydrate sources in habitats populated by lactobacilli. Moreover, oligosaccharide metabolism is essential for ecological fitness of lactobacilli. Disaccharide metabolism by lactobacilli is well understood; however, few data on the metabolism of higher oligosaccharides are available. Research on the ecology of intestinal microbiota as well as the commercial application of prebiotics has shifted the interest from (digestible) disaccharides to (indigestible) higher oligosaccharides. This review provides an overview on oligosaccharide metabolism in lactobacilli. Emphasis is placed on maltodextrins, isomalto-oligosaccharides, fructo-oligosaccharides, galacto-oligosaccharides, and raffinose-family oligosaccharides. Starch is also considered. Metabolism is discussed on the basis of metabolic studies related to oligosaccharide metabolism, information on the cellular location and substrate specificity of carbohydrate transport systems, glycosyl hydrolases and phorphorylases, and the presence of metabolic genes in genomes of 28 strains of lactobacilli. Metabolic pathways for disaccharide metabolism often also enable the metabolism of tri- and tetrasaccharides. However, with the exception of amylase and levansucrase, metabolic enzymes for oligosaccharide conversion are intracellular and oligosaccharide metabolism is limited by transport. This general restriction to intracellular glycosyl hydrolases differentiates lactobacilli from other bacteria that adapted to intestinal habitats, particularly Bifidobacterium spp.

/pdf/metabolism-of-oligosaccharides-and-starch-in-lactobacilli-a-36my8hjky6.pdf

Metabolism of oligosaccharides and starch in lactobacilli: a review.

Summary
Compatible solutes are a functional group of small, highly soluble organic molecules that demonstrate compatibility in high amounts with cellular metabolism. The accumulation of compatible solutes is often observed during the acclimation of organisms to adverse environmental conditions, particularly to salt and drought stress. Among cyanobacteria, sucrose, trehalose, glucosylglycerol and glycine betaine are used as major compatible solutes. Interestingly, a close correlation has been discovered between the final salt tolerance limit and the primary compatible solute in these organisms. In addition to the dominant compatible solutes, many strains accumulate mixtures of these compounds, including minor compounds such as glucosylglycerate or proline as secondary or tertiary solutes. In particular, the accumulation of sucrose and trehalose results in an increase in tolerance to general stresses such as desiccation and high temperatures. During recent years, the biochemical and molecular basis of compatible solute accumulation has been characterized using cyanobacterial model strains that comprise different salt tolerance groups. Based on these data, the distribution of genes involved in compatible solute synthesis among sequenced cyanobacterial genomes is reviewed, and thereby, the major compatible solutes and potential salt tolerance of these strains can be predicted. Knowledge regarding cyanobacterial salt tolerance is not only useful to characterize strain-specific adaptations to ecological niches, but it can also be used to generate cells with increased tolerance to adverse environmental conditions for biotechnological purposes.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1462-2920.2010.02366.x

Compatible solute biosynthesis in cyanobacteria

Enzymatic methods for glyco(diversification/randomization) of drugs and small molecules.

Glycosylation can significantly improve the physicochemical and biological properties of small molecules like vitamins, antibiotics, flavors, and fragrances. The chemical synthesis of glycosides is, however, far from trivial and involves multistep routes that generate lots of waste. In this review, biocatalytic alternatives are presented that offer both stricter specificities and higher yields. The advantages and disadvantages of different enzyme classes are discussed and illustrated with a number of recent examples. Progress in the field of enzyme engineering and screening are expected to result in new applications of biocatalytic glycosylation reactions in various industrial sectors.

/pdf/enzymatic-glycosylation-of-small-molecules-challenging-5d3swt7028.pdf

Enzymatic Glycosylation of Small Molecules: Challenging Substrates Require Tailored Catalysts

Recombinant sucrose phosphorylase from Leuconostoc mesenteroides: characterization, kinetic studies of transglucosylation, and application of immobilised enzyme for production of alpha-D-glucose 1-phosphate.

A high-yielding biocatalytic process for the production of 2-O-(alpha-D-glucopyranosyl)-sn-glycerol, a natural osmolyte and useful moisturizing ingredient.

Sucrose phosphorylase is a bacterial transglucosidase that catalyzes conversion of sucrose and phosphate into α-D-glucose-1-phosphate and D-fructose. The enzyme utilizes a glycoside hydrolase-like double displacement mechanism that involves a catalytically competent β-glucosyl enzyme intermediate. In addition to reaction with phosphate, glucosylated sucrose phosphorylase can undergo hydrolysis to yield α-D-glucose or it can decompose via glucosyl transfer to a hydroxy group in suitable acceptor molecules, giving new α-D-glucosidic products. The glucosyl acceptor specificity of sucrose phosphorylase is reviewed, focusing on applications of the enzyme in glucoside synthesis. Polyhydroxylated compounds such as sugars and sugar alcohols are often glucosylated efficiently. Aryl alcohols and different carboxylic acids also serve as acceptors for enzymatic transglucosylation. The natural osmolyte 2-O-(α-D-glucopyranosyl)-sn-glycerol (GG) was prepared by regioselective glucosylation of glycerol from sucro...

Sucrose phosphorylase: a powerful transglucosylation catalyst for synthesis of α-D-glucosides as industrial fine chemicals

Compatible solutes constitute a diverse class of low-molecular-mass organic molecules that are accumulated in high intracellular concentrations in response to the external stress of hyperosmolality or high temperature. Many of these compounds like alpha, alpha-trehalose are well known for their stabilizing effect on protein structure and could lead to development of more stable protein formulations. Negatively charged solutes like mannosylglycerate (R-2-O-alpha-D-mannopyranosyl-glycerate) are widespread among (hyper)thermophilic microorganisms and are thought to be exceptionally potent stabilizers of proteins under high-temperature denaturation conditions. To further inquire into the role of compound charge for protective function, we have compared two naturally occurring and structurally related solutes, glucosylglycerol (2-O-alpha-D-glucopyranosyl-sn-glycerol) and glucosylglycerate (R-2-O-alpha-D-glucopyranosyl-glycerate), as stabilizers of different enzymes undergoing inactivation through elevated temperature or freeze drying, and benchmarked their effects against that of alpha,alpha-trehalose. Glucosylglycerate in concentrations of >/=0.1 M was the most effective in preventing thermally induced loss of enzyme activity of lactate dehydrogenase, mannitol dehydrogenase, starch phosphorylase, and xylose reductase. alpha,alpha-Trehalose could usually be replaced by glucosylglycerol without compromising enzyme stability. Glucosylglycerol and glucosylglycerate afforded substantial (eightfold) protection to mannitol dehydrogenase during freeze drying.

Glucosylglycerol and glucosylglycerate as enzyme stabilizers.

Regioselective glucosylation of R-glycerate catalysed by sucrose phosphorylase in the presence of sucrose as the donor substrate provided the natural compatible solute (R)-2-O-α-D-glucopyranosyl glycerate with complete regioselectivity in an optimised synthetic yield of 90% R-glycerate converted and a concentration of about 270 mM.

Single-step enzymatic synthesis of (R)-2-O-alpha-D-glucopyranosyl glycerate, a compatible solute from micro-organisms that functions as a protein stabiliser.

Christiane Goedl

Papers

Recombinant sucrose phosphorylase from Leuconostoc mesenteroides: characterization, kinetic studies of transglucosylation, and application of immobilised enzyme for production of alpha-D-glucose 1-phosphate.

A high-yielding biocatalytic process for the production of 2-O-(alpha-D-glucopyranosyl)-sn-glycerol, a natural osmolyte and useful moisturizing ingredient.

Sucrose phosphorylase: a powerful transglucosylation catalyst for synthesis of α-D-glucosides as industrial fine chemicals

Glucosylglycerol and glucosylglycerate as enzyme stabilizers.

Single-step enzymatic synthesis of (R)-2-O-alpha-D-glucopyranosyl glycerate, a compatible solute from micro-organisms that functions as a protein stabiliser.