Nucleoside synthesis by immobilised bacterial whole cells

Continuous process technology for glucoside production from sucrose using a whole cell-derived solid catalyst of sucrose phosphorylase

Advanced biotransformation processes typically involve the upstream processing part performed continuously and interlinked tightly with the product isolation. Key in their development is a catalyst that is highly active, operationally robust, conveniently produced, and recyclable. A promising strategy to obtain such catalyst is to encapsulate enzymes as permeabilized whole cells in porous polymer materials. Here, we show immobilization of the sucrose phosphorylase from Bifidobacterium adolescentis (P134Q-variant) by encapsulating the corresponding E. coli cells into polyacrylamide. Applying the solid catalyst, we demonstrate continuous production of the commercial extremolyte 2-α-D-glucosyl-glycerol (2-GG) from sucrose and glycerol. The solid catalyst exhibited similar activity (≥70%) as the cell-free extract (~800 U g-1 cell wet weight) and showed excellent in-operando stability (40 °C) over 6 weeks in a packed-bed reactor. Systematic study of immobilization parameters related to catalyst activity led to the identification of cell loading and catalyst particle size as important factors of process optimization. Using glycerol in excess (1.8 M), we analyzed sucrose conversion dependent on space velocity (0.075-0.750 h-1) and revealed conditions for full conversion of up to 900 mM sucrose. The maximum 2-GG space-time yield reached was 45 g L-1 h-1 for a product concentration of 120 g L-1. Collectively, our study establishes a step-economic route towards a practical whole cell-derived solid catalyst of sucrose phosphorylase, enabling continuous production of glucosides from sucrose. This strengthens the current biomanufacturing of 2-GG, but also has significant replication potential for other sucrose-derived glucosides, promoting their industrial scale production using sucrose phosphorylase. KEY POINTS: • Cells of sucrose phosphorylase fixed in polyacrylamide were highly active and stable. • Solid catalyst was integrated with continuous flow to reach high process efficiency. • Generic process technology to efficiently produce glucosides from sucrose is shown.

New trends in the biocatalytic production of nucleosidic active pharmaceutical ingredients using 2'-deoxyribosyltransferases

Nowadays, pharmaceutical industry demands competitive and eco-friendly processes for active pharmaceutical ingredients (APIs) manufacturing. In this context, enzyme and whole-cell mediated processes offer an efficient, sustainable and cost-effective alternative to the traditional multi-step and environmentally-harmful chemical processes. Particularly, 2'-deoxyribosyltransferases (NDTs) have emerged as a novel synthetic alternative, not only to chemical but also to other enzyme-mediated synthetic processes. This review describes recent findings in the development and scaling up of NDTs as industrial biocatalysts, including the most relevant and recent examples of single enzymatic steps, multienzyme cascades, chemo-enzymatic approaches, and engineered biocatalysts. Finally, to reflect the inventive and innovative steps of NDT-mediated bioprocesses, a detailed analysis of recently granted patents, with specific focus on industrial synthesis of nucleoside-based APIs, is hereunder presented.

Decitabine bioproduction using a biocatalyst with improved stability by adding nanocomposites

A novel IDA-LaNDT derivative was able to reach the highest productivity in the biosynthesis of a well-known antitumoral agent called decitabine. However, the combination of two simple and inexpensive techniques such as ionic absorption and gel entrapment with the incorporation of a bionanocomposite such as bentonite significantly improved the stability of this biocatalyst. These modifications allowed the enhancement of storage stability (for at least 18 months), reusability (400 h of successive batches without significant loss of its initial activity), and thermal and solvent stability with respect to the non-entrapped derivative. Moreover, reaction conditions were optimized by increasing the solubility of 5-aza by dilution with dimethylsulfoxide. Therefore, a scale-up of the bioprocess was assayed using the developed biocatalyst, obtaining 221 mg/L·h of DAC. Finally, green parameters were calculated using the nanostabilized biocatalyst, whose results indicated that it was able to biosynthesize DAC by a smooth, cheap, and environmentally friendly methodology.

Whole Cell Entrapment Techniques

Microbial whole cells are efficient, ecological, and low-cost catalysts that have been successfully applied in the pharmaceutical, environmental, and alimentary industries, among others.Microorganism immobilization is a good way to carry out the bioprocess under preparative conditions. The main advantages of this methodology lie in their high operational stability, easy upstream separation, and bioprocess scale-up feasibility.Cell entrapment is the most widely used technique for whole cell immobilization. This technique-in which the cells are included within a rigid network-is porous enough to allow the diffusion of substrates and products, protects the selected microorganism from the reaction medium, and has high immobilization efficiency (100% in most cases).

Bioproduction of ribavirin by green microbial biotransformation

•

Biotransformation of ribavirin was performed by E. coli ATCC 12407, reaching yields of 86%.

•

This mesophile microorganism was successfully stabilized in agarose and polyacrylamide.

•

Biocatalyst immobilized in agarose could be reused during 270 h without activity loss.

•

Packed-bed bioreactor prototype was able to produce 95 mg ribavirin.

Ribavirin is an antiviral compound widely used in Hepatitis C Virus therapy. Biotransformation of this nucleoside analogue using Escherichia coli ATCC 12407 as biocatalyst is herein reported. Reaction parameters such as microorganism amounts, substrate ratio and temperature were optimized reaching conversion yields of 86%. Biocatalyst stability was enhanced by immobilization in agarose matrix. This immobilized biocatalyst was able to be reused for more than 270 h and could be stored during more than 4 months without activity loss. Batch and packed-bed reactors based on a stabilized biocatalyst were assayed for bioprocess scale-up. A continuous sustainable bioprocess was evaluated using a prototype packed-bed reactor, which allowed to produce 95 mg of ribavirin.

Finally, in this work an efficient green bioprocess for ribavirin bioproduction using a stabilized biocatalyst was developed.

An Efficient Chemoenzymatic Process for Preparation of Ribavirin

Ribavirin is an important antiviral drug, which is used for treatment of many diseases. The pilot-scale chemoenzymatic process for synthesis of the active pharmaceutical ingredient Ribavirin was developed with 32% overall yield and more than 99.5% purity. The described method includes the chemical synthesis of 1,2,4-triazole-3-carboxamide, which is a key intermediate and enzyme-catalyzed transglycosylation reaction for preparation of the desired product. 1,2,4-Triazole-3-carboxamide was synthesized from 5-amino-1,2,4-triazole-3-carboxylic acid by classical Chipen-Grinshtein method. Isolated fromE. сoliBL21(DE3)/pERPUPHHO1 strain the purine nucleoside phosphorylase was used as a biocatalytical system. All steps of this process were optimized and scaled.

Whole cell entrapment techniques

Microbial whole cells are efficient, ecological, and low-cost catalysts that have been successfully applied in the pharmaceutical, environmental, and alimentary industries, among others. Microorganism immobilization is a good way to carry out the bioprocess under preparative conditions. The main advantages of this methodology lie in their high operational stability, easy upstream separation and bioprocess scale-up feasibility. Cell entrapment is the most widely used technique for whole cell immobilization. This technique-in which the cells are included within a rigid network-is porous enough to allow the diffusion of substrates and products, protects the selected microorganism from the reaction medium, and has high immobilization efficiency (100 % in most cases).

Biotransformation of 2,6-diaminopurine nucleosides by immobilized Geobacillus stearothermophilus

An efficient and green bioprocess to obtain 2,6-diaminopurine nucleosides using thermophilic bacteria is herein reported. Geobacillus stearothermophilus CECT 43 showed a conversion rate of 90 and 83% at 2 h to obtain 2,6-diaminopurine-2'-deoxyriboside and 2,6-diaminopurine riboside, respectively. The selected biocatalyst was successfully stabilized in an agarose matrix and used to produce up to 23.4 g of 2,6-diaminopurine-2'-deoxyriboside in 240 h of process. These nucleoside analogues can be used as prodrug precursors or in antisense oligonucleotide synthesis.

Biosynthesis of anti-HCV compounds using thermophilic microorganisms

This work describes the application of thermophilic microorganisms for obtaining 6-halogenated purine nucleosides. Biosynthesis of 6-chloropurine-2′-deoxyriboside and 6-chloropurine riboside was achieved by Geobacillus stearothermophilus CECT 43 with a conversion of 90% and 68%, respectively. Furthermore, the selected microorganism was satisfactorily stabilized by immobilization in an agarose matrix. This biocatalyst can be reused at least 70 times without significant loss of activity, obtaining 379 mg/L of 6-chloropurine-2′-deoxyriboside. The obtained compounds can be used as antiviral agents.

Induction of nucleoside phosphorylase in Enterobacter aerogenes and enzymatic synthesis of adenine arabinoside

Nucleoside phosphorylases (NPases) were found to be induced in Enterobacter aerogenes DGO-04, and cytidine and cytidine 5'-monophosphate (CMP) were the best inducers. Five mmol/L to fifteen mmol/L cytidine or CMP could distinctly increase the activities of purine nucleoside phosphorylase (PNPase), uridine phosphorylase (UPase) and thymidine phosphorylase (TPase) when they were added into medium from 0 to 8 h. In the process of enzymatic synthesis of adenine arabinoside from adenine and uracil arabinoside with wet cells of Enterobacter aerogenes DGO-04 induced by cytidine or CMP, the reaction time could be shortened from 36 to 6 h. After enzymatic reaction the activity of NPase in the cells induced remained higher than that in the cells uninduced.

Low-temperature synthesis of 2'-deoxyadenosine using immobilized psychrotrophic microorganisms

Selective biocatalyzed synthesis of 2'-deoxyadenosine from 2'-deoxypyrimidine nucleosides was carried out using free or immobilized whole cells. The reaction was performed at 57 degrees C without secondary reactions. Two psychrotrophic microorganisms, Bacillus psychrosaccharolyticus and Psychrobacter immobilis, are described for the first time as active and specific strains for the synthesis of 2'-deoxyadenosine. Adenosine deaminase activity was not detected. Whole cells were immobilized in different matrixes. Calcium alginate and calcium pectate gave the best biocatalysts. The synthesis of 2'-deoxyadenosine follows an apparent first order kinetic expression. External mass transfer control was negligible as deduced from k(s), N(A), and Omega values. Internal mass transfer was the rate controlling step according to eta(T) and phi values.