Glucose biocatalytic conversion

Figure 2 In vitro Biocatalytic Conversion of Cellulose (Avicel, Lattice 20) with Cellulose (Spezyme) to Glucose...

The most important conversions in the context of green chemistry is with the help of enzymes. Enzymes are also referred to as biocatalysts and the transformations are referred to as biocatalytic conversions. Enzymes are now easily available and are an important tool in organic synthesis. The earliest biocatalytic conversion known to mankind is the manufacture of ethyl alcohol from molasses, the mother liquor left after the crystallisation of cane sugar from concentrated cane juice. This transformation is brought about by the enzyme invertase which converts sucrose into glucose and fructose and finally by the enzyme zymase which converts glucose and fiuctose into ethyl alcohol. It is well known that most of the antibiotics have been prepared using enzymes (enzymatic fermentation). 

Another example of the direct use of a renewable chemical is the biocatalytic conversion of D-glucose into vanillin used as a flavoring agent in food and beverages [12]. The use of a recombinant Escherichia coli biocatalyst in fermentation offers many advantages over the synthetic vanillin manufactme based on the use of... 

Bacterial De-Novo Synthesis. The basic idea behind this variant is to use the synthetic potential of bacteria to produce the indole precursor (Scheme 3). Although indole (23) does not occur as an intermediate in bacterial metabolism, it appears as an enzyme-linked intermediate in the biocatalytic transformation ofD-glucose (17) to L-tryptophan (22). The crucial biosynthetic step is the conversion of indole-3-glycerine phosphate (21) to L-tryptophan (22) by the enzyme tryptophan synthase. 

The biocatalytic microbe-based conversion of o-glucose into ds,ds-muconic acid and the subsequent hydrogenation of the latter into AA has been proposed by Draths and Frost [42a, bj. This synthesis is emblematic of an environmentally benign process, making use of a renewable raw material for the synthesis of a commodity chemical by means of an intrinsically safe process. 

Figure 5. The biocatalytic pathway (boxed arrows) created for microbial conversion of D-glucose into cis, cw-muconate from the perspective of the biochemical pathways from which the enzymes were recruited. Conversion of D-glucose into DHS requires transketolase (tkt) from the pentose phosphate pathway and DAHP synthase (aroF, aroG, aroH)y DHQ synthase aroB and DHQ dehydratase aroD) from the common pathway of aromatic amino acid biosynthesis. Conversion of DHS into catechol requires DHS dehydratase (aroZ, enzyme A) from hydroaromatic catabolism, protocatechuate decarboxylase aroY, enzyme B), and catechol 1,2-dioxygenase (caM, enzyme C) from the benzoate branch of the p-ketoadipate pathway. (Adapted and reproduced with permission from ref. 21.)...

Uridine diphosphate glucose (UDP-Glc) serves as a glucosyl donor in many enzymatic glycosylation processes. A multiple enzyme, one-pot, biocatalytic system was developed for the synthesis of UDP-Glc from low cost raw materials maltodextrin and uridine triphosphate. Three enzymes needed for the synthesis of UDP-Glc (maltodextrin phosphorylase, glucose-l-phosphate thymidyly-transferase, and pyrophosphatase) were expressed in Escherichia coli and then immobilized individually on amino-functionalized magnetic nanoparticles. The conditions for biocatalysis were optimized and the immobilized multiple-enzyme biocatalyst could be easily recovered and reused up to five times in repeated syntheses of UDP-Glc. After a simple purification, approximately 630 mg of crystallized UDP-Glc was obtained from 1 L of reaction mixture, with a moderate yield of around 50% (UTP conversion) at very low cost. ... 

This chapter is an overview of architectures adopted for the catalytic/biocatalytic composites used in wide applications like the biomass valorization or fine chemical industry. On this perspective, the chapter updates the reader with the most fresh examples of construction designs and concepts considered for the synthesis of such composites. Their catalytic properties result from the introduction of catalytic functionalities and vary from inorganic metal species e.g., Ru, Ir, Pd, or Rh) to well-organized biochemical structures like enzymes e.g., lipase, peroxidase, (3-galactosidase) or whole cells. Catalytic/biocatalytic procedures for the biomass conversion into platform molecules e.g., glucose, GVL, Me-THF, sorbitol, succinic acid, and glycerol) and their further transformation into value-added products are detailed in order to make understandable the utility of these complex architectures and to associate the composite properties to their performances, versatility, and robustness. 

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