Development of an Enzyme Cascade System for the Synthesis of Enantiomerically Pure D-Amino Acids Utilizing Ancestral L-Amino Acid Oxidase

Enantiomerically pure D-amino acids hold significant potential as precursors for synthesizing various fine chemicals, including peptide-based drugs and other pharmaceuticals. This study focuses on establishing an enzymatic cascade system capable of converting various L-amino acids into their D-isomers. The system integrates four enzymes: ancestral L-amino acid oxidase (AncLAAO-N4), D-amino acid dehydrogenase (DAADH), D-glucose dehydrogenase (GDH), and catalase. AncLAAO-N4 initiates the process by converting L-amino acids to corresponding keto acids, which are then stereo-selectively aminated to D-amino acids by DAADH using NADPH and NH4Cl. Concurrently, any generated H2O2 is decomposed into O2 and H2O by catalase, while GDH regenerates NADPH from D-glucose. Optimization of reaction conditions and substrate concentrations enabled the successful synthesis of five D-amino acids, including a D-Phe derivative, three D-Trp derivatives, and D-phenylglycine, all with high enantiopurity (>99 % ee) at a preparative scale (>100 mg). This system demonstrates a versatile approach for producing a diverse array of D-amino acids.

Ionic liquid modification reshapes the substrate pockets of lipase to boost its stability and activity in vitamin E succinate synthesis

BACKGROUND

The relative low stability, reusability and activity of enzymes made the industrial production of vitamin E succinate (VES) can only be performed with complex processes and high cost using chemical methods. To address these issues, in the present study, an ionic liquids (ILs) modification strategy was developed to improve the activity and stability of lipases in VES synthesis.

RESULTS

The results showed that the [1-butyl-3-methyl imidazole] [N-acetyl-l-proline] ILs modified Candida rugosa lipase (CRL) has the highest modification degree (48.28%), activity (774 U g-1 ), thermostability and solvent tolerance in three selected modifiers. Additionally, after reaction condition optimization, the highest yield of VES can be improved to 95.18% at 45 °C for 15 h, which was significantly improved compared to some previous studies.

CONCLUSION

In the present study, a high-efficiency VES synthesis strategy was successfully developed via modification of lipase. Moreover, the mechanism by which ILs modification can enhance the activity and stability of lipase was investigated via both experimental and computational-aided methods. Molecular dynamics simulation suggested that ILs modification changed the geometry of Phe344 from flat to upright, which significantly reshaped and enhanced the size of substrate binding pocket of CRL. It is also agreement with our circular dichroism and fluorescence spectroscopy results, which suggested that the modification changed the secondary structure of CRL to a certain extent. The larger pocket also endowed the suitable binding pose of succinate, which made the hydrogen bonds between succinate and active site Ser209 become stronger, and thus improving the yield of VES. © 2023 Society of Chemical Industry.

Enzymatic synthesis of furan-based copolymers: Material characterization and potential for biomedical applications

BACKGROUND

Today's growing demand for advanced and sustainable polyester materials is driven by an increasing awareness of the environmental impact of traditional materials, emphasizing the need for eco-friendly alternatives. Sustainability has become central in materials development, including the biomedical area, where biobased and environmentally friendly solutions are a rapidly growing field.

OBJECTIVES

This research aims to comprehensively evaluate a new enzymatically catalyzed furan-based copolymer, poly(decamethylene furanoate)-co-(dilinoleic furanoate) (PDF-DLF), with a 70-30 wt% hard-to-soft segment ratio. Then, its performance across medical applications is explored, with a particular focus on its potential as a nanofibrous scaffolding material.

MATERIAL AND METHODS

PDF-DLF was synthesized from biobased monomers using Candida antarctica lipase B (CAL-B) as the biocatalyst. Material characterization included dynamic mechan‑ical thermal analysis (DMTA) to assess the mechanical behavior and thermal properties. Enzymatic degradation studies determined biodegradability, while cytotoxicity tests established in vitro biocompatibility. The copolymer was electrospun into nanofibers, with scanning electron microscopy (SEM) employed to analyze their morphology.

RESULTS

PDF-DLF displays mechanical and thermal properties indicating high storage modulus and 2 main temperature transitions. Enzymatic degradation studies and cytotoxicity assessments confirm biodegradability and in vitro biocompatibility. Electrospinning successfully transformed the copolymer into nanofibers with diameters ranging from 500 nm to 700 nm.

CONCLUSIONS

This study significantly advances our understanding of sustainable polyesters with versatile processing capabilities. The successful electrospinning highlights its potential as a biodegradable scaffold for medical engineering, supported by biocompatibility and sufficient mechanical properties. It opens new opportunities for sustainable materials in critical biomedical industries, including tissue engineering.

Chemoenzymatic Synthesis of GAA-7 Glycan Analogues and Evaluation of Their Neuritogenic Activities

Ganglioside GAA-7 exhibits higher neurite outgrowth than ganglioside GM1a and most echinodermatous gangliosides (EGs) when tested on neuron-like rat adrenal pheochromocytoma (PC12) cells in the presence of nerve growth factor (NGF). The unique structure of GAA-7 glycan, containing an uncommon sialic acid (8-O-methyl-N-glycolylneuraminic acid) and sialic acid-α-2,3-GalNAc linkage, makes it challenging to synthesize. We recently developed a streamlined method to chemoenzymatically synthesize GAA-7 glycan and employed this modular strategy to efficiently prepare a library of GAA-7 glycan analogues incorporating N-modified or 8-methoxyl sialic acids. Most of these synthetic glycans exhibited moderate efficacy in promoting neuronal differentiation of PC12 cells. Among them, the analogue containing common sialic acid shows greater potential than the GAA-7 glycan itself. This result reveals that methoxy modification is not essential for neurite outgrowth. Consequently, the readily available analogue presents a promising model for further biological investigations.

Sugar-Based Monoester Surfactants: Synthetic Methodologies, Properties, and Biological Activities

Glycolipids are biocompatible and biodegradable amphiphilic compounds characterized by a great scientific interest for their potential applications in various technological areas, including pharmaceuticals, cosmetics, agriculture, and food production. This report summarizes the available synthetic methodologies, physicochemical properties, and biological activity of sugar fatty acid ester surfactants, with a particular focus on 6-O-glucose, 6-O-mannose, 6-O-sucrose, and 6'-O-lactose ones. In detail, the synthetic approaches to this class of compounds, such as enzymatic lipase-catalyzed and traditional chemical (e.g., acyl chloride, Steglich, Mitsunobu) esterifications, are reported. Moreover, aspects related to the surface activity of these amphiphiles, such as their ability to decrease surface tension, critical micelle concentration, and emulsifying and foaming ability, are described. Biological applications with a focus on the permeability-enhancing effect across the skin or mucosa, antimicrobial and antifungal activities, as well as antibiofilm properties, are also presented. The information reported here on sugar-based ester surfactants is helpful to broaden the interest and the possible innovative applications of this class of amphiphiles in different technological fields in the future.

Straightforward Enzymatic Methacrylation of Poly(Glycerol Adipate) for Potential Applications as UV Curing Systems

Enzymatic one-pot synthesis procedures in a one-step and two-step monomers addition were developed to obtain poly(glycerol adipate) macromers with methacrylate end-functional groups under the presence of 1 and 3 wt% of Candida antarctica lipase B (CALB). Glycerol, divinyl adipate, and vinyl methacrylate were enzymatically reacted (vinyl methacrylate was either present from the beginning in the monomers solution or slowly dropped after 6 h of reaction) in tetrahydrofuran (THF) at 40 °C over 48 h. Macromers with a methacrylate end groups fraction of ≈52% in a simple one-pot one-step procedure were obtained with molecular weights (M_n) of ≈7500-7900 g/mol. The obtained products under the one-pot one-step and two steps synthesis procedures carried out using 1 and 3 wt% of a CALB enzymatic catalyst were profusely characterized by NMR (¹H and ¹³C), MALDI-TOF MS, and SEC. The methacrylate functional macromers obtained with the different procedures and 1 wt% of CALB were combined with an Irgacure^® 369 initiator to undergo homopolymerization under UV irradiation for 10 and 30 min, in order to test their potential to obtain amorphous networks within minutes with similar properties to those typically obtained by complex acrylation/methacrylation procedures, which need multiple purification steps and harsh reagents such as acyl chlorides. To the best of our knowledge, this is the first time that it has been demonstrated that the obtention of methacrylate-functional predominantly linear macromers based on poly(glycerol adipate) is able to be UV crosslinked in a simple one-step procedure.

Rational Design of Meso-Diaminopimelate Dehydrogenase with Enhanced Reductive Amination Activity for Efficient Production of d-p-Hydroxyphenylglycine

d-p-hydroxyphenylglycine (d-HPG) is an important intermediate in the pharmaceutical industry. In this study, a tri-enzyme cascade for the production of d-HPG from l-HPG was designed. However, the amination activity of Prevotella timonensis meso-diaminopimelate dehydrogenase (PtDAPDH) toward 4-hydroxyphenylglyoxylate (HPGA) was identified as the rate-limiting step. To overcome this issue, the crystal structure of PtDAPDH was solved, and a "binding pocket and conformation remodeling" strategy was developed to improve the catalytic activity toward HPGA. The best variant obtained, PtDAPDHM4, exhibited a catalytic efficiency (kcat/Km) that was 26.75-fold higher than that of the wild type. This improvement was due to the enlarged substrate-binding pocket and enhanced hydrogen bond networks around the active center; meanwhile, the increased number of interdomain residue interactions drove the conformation distribution toward the closed state. Under optimal transformation conditions, PtDAPDHM4 produced 19.8 g/L d-HPG from 40 g/L racemate DL-HPG in a 3 L fermenter within 10 h, with 49.5% conversion and >99% enantiomeric excess. Our study provides an efficient three-enzyme cascade pathway for the industrial production of d-HPG from racemate DL-HPG. IMPORTANCE d-p-hydroxyphenylglycine (d-HPG) is an important intermediate in the synthesis of antimicrobial compounds. d-HPG is mainly produced via chemical and enzymatic approaches, and enzymatic asymmetric amination employing diaminopimelate dehydrogenase (DAPDH) is considered an attractive method. However, the low catalytic activity of DAPDH toward bulky 2-keto acids limits its applications. In this study, we identified a DAPDH from Prevotella timonensis and created a mutant, PtDAPDHM4, which exhibited a catalytic efficiency (kcat/Km) toward 4-hydroxyphenylglyoxylate that was 26.75-fold higher than that of the wild type. The novel strategy developed in this study has practical value for the production of d-HPG from inexpensive racemate DL-HPG.

Enzymatic Bioconjugation: A Perspective from the Pharmaceutical Industry

Enzymes have firmly established themselves as bespoke catalysts for small molecule transformations in the pharmaceutical industry, from early research and development stages to large-scale production. In principle, their exquisite selectivity and rate acceleration can also be leveraged for modifying macromolecules to form bioconjugates. However, available catalysts face stiff competition from other bioorthogonal chemistries. In this Perspective, we seek to illuminate applications of enzymatic bioconjugation in the face of an expanding palette of new drug modalities. With these applications, we wish to highlight some examples of current successes and pitfalls of using enzymes for bioconjugation along the pipeline and try to illustrate opportunities for further development.

Dihydrocaffeic Acid-Is It the Less Known but Equally Valuable Phenolic Acid?

Dihydrocaffeic acid (DHCA) is a phenolic acid bearing a catechol ring and three-carbon side chain. Despite its being found in minor amounts in numerous plants and fungi of different origins, it has attracted the interest of various research groups in many fields of science, from food to biomedical applications. The review article presented herein aims to show a wider audience the health benefits and therapeutic, industrial, and nutritional potential of dihydrocaffeic acid, by sheddinglight on its occurrence, biosynthesis, bioavailability, and metabolism. The scientific literature describes at least 70 different derivatives of dihydrocaffeic acid, both those occurring naturally and those obtained via chemical and enzymatic methods. Among the most frequently used enzymes that were applied for the modification of the parent DHCA structure, there are lipases that allow for obtaining esters and phenolidips, tyrosinases used for the formation of the catechol ring, and laccases to functionalize this phenolic acid. In many studies, both in vitro and in vivo, the protective effect of DHCA and its derivatives on cells subjected to oxidative stress and inflammation were acknowledged.

Maltooligosaccharides: Properties, Production and Applications

Maltooligosaccharides (MOS) are homooligosaccharides that consist of 3-10 glucose molecules linked by α-1,4 glycosidic bonds. As they have physiological functions, they are commonly used as ingredients in nutritional products and functional foods. Many researchers have investigated the potential applications of MOS and their derivatives in the pharmaceutical industry. In this review, we summarized the properties and methods of fabricating MOS and their derivatives, including sulfated and non-sulfated alkylMOS. For preparing MOS, different enzymatic strategies have been proposed by various researchers, using α-amylases, maltooligosaccharide-forming amylases, or glycosyltransferases as effective biocatalysts. Many researchers have focused on using immobilized biocatalysts and downstream processes for MOS production. This review also provides an overview of the current challenges and future trends of MOS production.

Lipase-Catalyzed Synthesis and Biological Evaluation of N-Picolineamides as Trypanosoma cruzi Antiproliferative Agents

In our search for new safe antiparasitic agents, an enzymatic pathway was applied to synthesize a series of N-pyridinylmethyl amides derived from structurally different carboxylic acids. Thirty derivatives, including 11 new compounds, were prepared through lipase-catalyzed acylation in excellent yields. In order to optimize the synthetic methodology, the impact of different reaction parameters was analyzed. Some compounds were evaluated as antiproliferative agents against Trypanosoma cruzi, the parasite responsible for American trypanosomiasis (Chagas' disease). Some of them showed significant activity as parasite proliferation inhibitors. Amides derived from 2-aminopicoline and stearic and elaidic acids were as potent as nifurtimox against the amastigote form of T. cruzi, the clinically relevant form of the parasite. Even more, a powerful synergism between nifurtimox and N-(pyridin-2-ylmethyl)stereamide was observed, almost completely inhibiting the proliferation of the parasite. Besides, the obtained compounds showed no toxicity in Vero cells, making them excellent potential candidates as lead drugs.

Enzymatic Synthesis of Ascorbyl Palmitate in a Rotating Bed Reactor

Ascorbyl palmitate, an ascorbic acid ester, is an important amphipathic antioxidant that has several applications in foods, pharmaceuticals, and cosmetics. The enzymatic synthesis of ascorbyl palmitate is very attractive, but few efforts have been made to address its process scale-up and implementation. This study aimed at evaluating the enzymatic synthesis of ascorbyl palmitate in a rotating basket reactor operated in sequential batches. Different commercial immobilized lipases were tested, and the most suitable reaction conditions were established. Among those lipases studied were Amano Lipase PS, Lipozyme^® TL IM, Lipozyme^® Novo 40086, Lipozyme^® RM IM and Lipozyme^® 435. Initially, the enzymes were screened based on previously defined synthesis conditions, showing clear differences in behavior. Lipozyme^® 435 proved to be the best catalyst, reaching the highest values of initial reaction rate and yield. Therefore, it was selected for the following studies. Among the solvents assayed, 2-methyl-2-butanol and acetone showed the highest yields, but the operational stability of the catalyst was better in 2-methyl-2-butanol. The tests in a basket reactor showed great potential for large-scale application. Yields remained over 80% after four sequential batches, and the basket allowed for easy catalyst recycling. The results obtained in basket reactor are certainly a contribution to the enzymatic synthesis of ascorbyl palmitate as a competitive alternative to chemical synthesis. This may inspire future cost-effectiveness studies of the process to assess its potential as a viable alternative to be implemented.

Modified Nucleotides for Chemical and Enzymatic Synthesis of Therapeutic RNA

In recent years, RNA has emerged as a medium with a broad spectrum of therapeutic potential, however, for years, a group of short RNA fragments was studied and considered therapeutic molecules. In nature, RNA plays both functions, with coding and non-coding potential. For RNA, like any other therapeutic, to be used clinically, certain barriers must be crossed. Among them, there are biocompatibility, relatively low toxicity, bioavailability, increased stability, target efficiency and low off-target effects. In the case of RNA, most of these obstacles can be overcome by incorporating modified nucleotides into its structure. This may be achieved by both, in vitro and in vivo biosynthetic methods, as well as chemical synthesis. Some advantages and disadvantages of each approach are summarized here. The wide range of nucleotide analogues has been tested for their utility as monomers for RNA synthesis. Many of them have been successfully implemented, and a lot of pre-clinical and clinical studies involving modified RNA have been carried out. Some of these medications have already been introduced into clinics. After the huge success of RNA-based vaccines that were introduced into widespread use in 2020, and the introduction to the market of some RNA-based drugs, RNA therapeutics containing modified nucleotides appear to be the future of medicine.

The Synthetic Approaches for Preparation of Indigo and Applications in Denim Industry

This paper describes indigo chemistry and its brief scientific history beginning with the first characterization and chemical synthesis of indigo via various precursors such as isatin, cinnamic acid, 2-nitrobenzaldehyde, anthranilic acid, N-phenylglycine, aniline, and indole. Furthermore, alternative methods such as eco-friendly microbial synthesis of indigo using a variety of enzymes are reported: Cytochrome P450 monooxygenases, flavin-containing monooxygenases, and unspecific peroxygenases. Subsequently, the application of indigo in the denim industry, reduction methods (chemical, electrochemical, enzymatic and catalytic) and dyeing methods (all parameters in dyeing, ring dye) are discussed. In addition, the main reason for the use of indigo in the denim industry is briefly explained.

Different methods of synthesizing poly(glycerol sebacate) (PGS): A review

Poly(glycerol sebacate) (PGS) is a biodegradable elastomer that has attracted increasing attention as a potential material for applications in biological tissue engineering. The conventional method of synthesis, first described in 2002, is based on the polycondensation of glycerol and sebacic acid, but it is a time-consuming and energy-intensive process. In recent years, new approaches for producing PGS, PGS blends, and PGS copolymers have been reported to not only reduce the time and energy required to obtain the final material but also to adjust the properties and processability of the PGS-based materials based on the desired applications. This review compiles more than 20 years of PGS synthesis reports, reported inconsistencies, and proposed alternatives to more rapidly produce PGS polymer structures or PGS derivatives with tailor-made properties. Synthesis conditions such as temperature, reaction time, reagent ratio, atmosphere, catalysts, microwave-assisted synthesis, and PGS modifications (urethane and acrylate groups, blends, and copolymers) were revisited to present and discuss the diverse alternatives to produce and adapt PGS.

Enzymatic synthesis of anhydroicaritin, baohuoside and icariin

Anhydroicaritin (1a), baohuoside (1b) and icariin (1c) were recognized as major pharmacologically active ingredients of Epimedium plants. Their primary means of acquisition were chemical isolation from plants. However, it suffers from low yield, environmental pollution and shortage of plants. Herein, to remedy these problems, biosynthesis was explored to obtain the three active ingredients. Fortunately, with SfFPT as 8-prenyltransferase, EpPF3RT and Ep7GT as glycosyltransferases, kaempferide (1) was transferred to 1a, 1b and 1c enzymatically. Thus, we report the details of this method. This approach represents a promising environmental friendly alternative for the production of these compounds from an abundant analogue.

[Comparison of three α-glucosidases from different sources in the synthesis of L-ascorbic acid 2-glucoside]

_L-ascorbic acid 2-glucoside (AA-2G) is a derivative of _L-ascorbic acid (_L-AA). Compared with _L-AA, it has good stability and is easily decomposed by enzyme in the human body. α-Glucosidase (AG) was the first enzyme found capable of producing AA-2G. However, researches on this enzyme is still in infancy. We took AG derived from Aspergillus niger (AAG), Japanese rice (JrAG) and Rattus rattus (RAG), and compared their specific enzymatic activity and transglycosidation rate, with the aim to improve the synthesis of AA-2G by the transglycosidation of AG. The genes encoding these three different AG were cloned and expressed in engineered yeast. The conditions for the transglycosidation reaction of these three enzymes were optimized and the transglycosidation efficiency and yield of AA-2G under the optimized conditions were compared. The specific activity of AAG reached 1.0 U/mg, while the yield of AA-2G reached 153.1 mg/L with a transglycosidation rate of 0.5%. The specific activity of RAG reached 0.4 U/mg, while the yield of AA-2G reached 861.0 mg/L with a transglycosidation rate of 2.5%. JrAG showed the highest specific activity and transglycosidation rate. The enzyme specific activity of JrAG reached 1.9 U/mg, while the yield of AA-2G reached 2 577.2 mg/L with a transglycosidation rate of 7.6%, much higher than that of the other two glucosidases. JrAG may thus have potential to improve the synthesis of AA-2G.

Effect of Starch Primers on the Fine Structure of Enzymatically Synthesized Glycogen-like Glucan

Glycogen-like glucan (GnG) is a unique hyperbranched polysaccharide nanoparticle which is drawing increasing attention due to its biodegradability and abundant short branches that can be functionalized. Because starch and GnG are both composed of glucose residues and have similar glucosidic bonds, GnG could be fabricated by sucrose phosphorylase, α-glucan phosphorylase, and branching enzymes from starch primers and sucrose. In this study, high-amylose starch, normal starch, and waxy corn starch were used as primers to synthesize GnG, and their impact on the fine structure of GnG was investigated. Structural analysis indicated that with increasing content of amylopectin in the starch primer, the proportion of short chains in GnG decreased, and the degree of β-amylolysis and α-amylolysis was enhanced. Amylose in the primer contributed to a compact and homogeneous structure of GnG, while amylopectin triggered the formation of branch points with a more open distribution. These findings provide a new strategy for regulating the fine structure of GnG.

Enzymatic Synthesis of Diacylglycerol-Enriched Oil by Two-Step Vacuum-Mediated Conversion of Fatty Acid Ethyl Ester and Fatty Acid From Soy Sauce By-Product Oil as Lipid-Lowering Functional Oil

Soy sauce by-product oil (SSBO), a by-product of the soy sauce production process, is the lack of utilization due to an abundance of free fatty acid (FFA) and fatty acid ethyl ester (EE). The utilization of low-cost SSBO to produce value-added diacylglycerol (DAG)-enriched oil and its applications are promising for the sustainability of the oil industry. The objective of this study was to utilize SSBO containing a high content of EE and FFA as raw material to synthesize DAG-enriched oil and to evaluate its nutritional properties in fish. Based on different behaviors between the glycerolysis of EE and the esterification of FFA in one-pot enzymatic catalysis, a two-step vacuum-mediated conversion was developed for the maximum conversions of EE and FFA to DAG. After optimization, the maximum DAG yield (66.76%) and EE and FFA conversions (96 and 93%, respectively) were obtained under the following optimized conditions: lipase loading 3%, temperature 38°C, substrate molar ratio (glycerol/FFA and EE) 21:40, a vacuum combination of 566 mmHg within the initial 10 h and 47 mmHg from the 10th to 14th hour. Further nutritional study in fish suggested that the consumption of DAG-enriched oil was safe and served as a functional oil to lower lipid levels in serum and liver, decrease lipid accumulation and increase protein content in body and muscle tissues, and change fatty acid composition in muscle tissues. Overall, these findings were vital for the effective utilization of SSBO resources and the development of future applications for DAG-enriched oil as lipid-lowering functional oil in food.

Synthesis and Biological Characterization of the New Glycolipid Lactose Undecylenate (URB1418)

As a follow-up to our previous studies on glycolipid surfactants, a new molecule, that is lactose 6′-O-undecylenate (URB1418), was investigated. To this end, a practical synthesis and studies aimed at exploring its specific properties were carried out. URB1418 showed antifungal activities against Trichophyton rubrum F2 and Candida albicans ATCC 10231 (MIC 512 μg/mL) and no significant antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. At the same time, it presented anti-inflammatory properties, as documented by the dose-dependent reduction in LPS-induced NO release in RAW 264.7 cells, while a low antioxidant capacity in the range of concentrations tested (EC50 > 200 µM) was also observed. Moreover, URB1418 offers the advantage of being more stable than the reference polyunsaturated lactose esters and of being synthesized using a “green” procedure, involving an enzymatic method, high yield and low manufacturing cost. For all these reasons and the absence of toxicity (HaCaT cells), the new glycolipid presented herein could be considered an interesting compound for applications in various fields.

Engineered Glycosidases for the Synthesis of Analogs of Human Milk Oligosaccharides

Enzymatic synthesis is an elegant biocompatible approach to complex compounds such as human milk oligosaccharides (HMOs). These compounds are vital for healthy neonatal development with a positive impact on the immune system. Although HMOs may be prepared by glycosyltransferases, this pathway is often complicated by the high price of sugar nucleotides, stringent substrate specificity, and low enzyme stability. Engineered glycosidases (EC 3.2.1) represent a good synthetic alternative, especially if variations in the substrate structure are desired. Site-directed mutagenesis can improve the synthetic process with higher yields and/or increased reaction selectivity. So far, the synthesis of human milk oligosaccharides by glycosidases has mostly been limited to analytical reactions with mass spectrometry detection. The present work reveals the potential of a library of engineered glycosidases in the preparative synthesis of three tetrasaccharides derived from lacto-N-tetraose (Galβ4GlcNAcβ3Galβ4Glc), employing sequential cascade reactions catalyzed by β3-N-acetylhexosaminidase BbhI from Bifidobacterium bifidum, β4-galactosidase BgaD-B from Bacillus circulans, β4-N-acetylgalactosaminidase from Talaromyces flavus, and β3-galactosynthase BgaC from B. circulans. The reaction products were isolated and structurally characterized. This work expands the insight into the multi-step catalysis by glycosidases and shows the path to modified derivatives of complex carbohydrates that cannot be prepared by standard glycosyltransferase methods.

Efficient Production of Naringin Acetate with Different Acyl Donors via Enzymatic Transesterification by Lipases

Naringin, one of the citrus flavonoids and known as a natural antioxidant, has limited bioavailability owing to its low stability and solubility. However, naringin esters formed via acylation have recently been reported to possess improved physical and chemical properties. The development of these compounds has a great potential in the food, cosmetic and pharmaceutical industries, but low conversion and productivity are barriers to industrial applications. This study aimed to improve the conversion of naringin acetate, which is formed via the enzymatic reaction between naringin and an acyl donor. An optimal reaction condition was determined by evaluating the effect of various variables (enzyme type, enzyme concentration, acyl donor, molar ratio of reactants, reaction temperature, and solvent) on the synthesis of naringin acetate. The optimal condition was as follows: 3 g/L of Lipozyme TL IM, molar ratio of 1:5 (naringin:acyl donor), reaction temperature of 40 °C, and acetonitrile as the reaction solvent. Under this condition, the maximum conversion to naringin acetate from acetic anhydride and vinyl acetate was achieved at approximately 98.5% (8 h) and 97.5% (24 h), respectively. Compared to the previously reported values, a high conversion was achieved within a short time, confirming the commercial potential of the process.

Enzymatic Catalysis in Favor of Blocky Structure and Higher Crystallinity of Poly(Butylene Succinate)-Co-(Dilinoleic Succinate) (PBS-DLS) Copolymers of Variable Segmental Composition

To systematically investigate the synthesis of poly(butylene succinate)-co-(dilinoleic succinate) (PBS-DLS) copolymers and to enrich the library of polyesters synthesized via a sustainable route, we conducted a two-step polycondensation using fully biobased monomers such as diethyl succinate (DS), 1,4-butanediol (1,4-BD) and dilinoleic diol (DLD) in diphenyl ether, using Candida Antarctica lipase B (CAL-B) as biocatalyst. A series of PBS-DLS copolyesters with a 90-10, 70-30 and 50-50 wt% of hard (PBS) to soft (DLS) segments ratio were compared to their counterparts, which were synthesized using heterogenous titanium dioxide/silicon dioxide (TiO₂/SiO₂) catalyst. Chemical structure and molecular characteristics of resulting copolymers were assessed using nuclear magnetic spectroscopy (¹H- and ¹³C-NMR) and gel permeation chromatography (GPC), whereas thermal and thermomechanical properties as well as crystallization behavior were investigated by differential scanning microscopy (DSC), dynamic mechanical thermal analysis (DMTA), digital holographic microscopy (DHM) and X-ray diffraction (XRD). The obtained results showed that, depending on the type of catalyst, we can control parameters related to blockiness and crystallinity of copolymers. Materials synthesized using CAL-B catalysts possess more blocky segmental distribution and higher crystallinity in contrast to materials synthesized using heterogenous catalysts, as revealed by DSC, XRD and DHM measurements.

Synthesis of C6-modified mannose 1-phosphates and evaluation of derived sugar nucleotides against GDP-mannose dehydrogenase

Sufferers of cystic fibrosis are at significant risk of contracting chronic bacterial lung infections. The dominant pathogen in these cases is mucoid Pseudomonas aeruginosa. Such infections are characterised by overproduction of the exopolysaccharide alginate. We present herein the design and chemoenzymatic synthesis of sugar nucleotide tools to probe a critical enzyme within alginate biosynthesis, GDP-mannose dehydrogenase (GMD). We first synthesise C6-modified glycosyl 1-phosphates, incorporating 6-amino, 6-chloro and 6-sulfhydryl groups, followed by their evaluation as substrates for enzymatic pyrophosphorylative coupling. The development of this methodology enables access to GDP 6-chloro-6-deoxy-ᴅ-mannose and its evaluation against GMD.

Controlling the Fine Structure of Glycogen-like Glucan by Rational Enzymatic Synthesis

Glycogen-like glucan (GnG), a hyperbranched glucose polymer, has been receiving increasing attention to generate synthetic polymers and nanoparticles. Importantly, different branching patterns strongly influence the functionality of GnG. To uncover ways of obtaining different GnG branching patterns, a series of GnG with radius from 22.03 to 27.06 nm were synthesized using sucrose phosphorylase, α-glucan phosphorylase (GP), and branching enzyme (BE). Adjusting the relative activity ratio of GP and BE (GP/BE) made the molecular weight (MW) distribution of intermediate GnG products follow two different paths. At a low GP/BE, the GnG developed from "small to large" during the synthetic process, with the MW increasing from 6.15 × 10⁶ to 1.21 × 10⁷ g/mol, and possessed a compact structure. By contrast, a high GP/BE caused the "large to small" model, with the MW reduction of GnG from 1.62 × 10⁷ to 1.21 × 10⁷ g/mol, and created a loose external structure. The higher GP activity promoted the elongation of external chains and restrained chain transfer by the BE to the inner zone of GnG, which would modulate the loose-tight structure of GnG. These findings provide new useful insights into the construction of structurally well-defined nanoparticles.

6'-O-Lactose Ester Surfactants as an Innovative Opportunity in the Pharmaceutical Field: From Synthetic Methods to Biological Applications

Glycolipid surfactants are biocompatible and biodegradable compounds characterized by potential applications in various sectors including pharmaceuticals, cosmetics, agriculture, and food production. A specific overview regarding synthetic methodologies and properties of 6′-lactose-based surfactants is presented herein, particularly all the synthetic approaches to this class of lactose esters, such as enzymatic and traditional organic syntheses. Moreover, detailed descriptions of physicochemical data and biocompatibility properties of these molecules, that is, surface tension, critical micelle concentration, emulsifying ability, foaming, particle size distribution, biocompatibility, and safety, are described. Biological applications with a focus on permeability enhancing, antimicrobial activity, and antibiofilm properties of 6′-lactose-based esters are also reported.

Novel dTDP-l-Rhamnose Synthetic Enzymes (RmlABCD) From Saccharothrix syringae CGMCC 4.1716 for One-Pot Four-Enzyme Synthesis of dTDP-l-Rhamnose

Deoxythymidine diphospho-l-rhamnose (dTDP-l-rhamnose) is used by prokaryotic rhamnosyltransferases as the glycosyl donor for the synthesis of rhamnose-containing polysaccharides and compounds that have potential in pharmaceutical development, so its efficient synthesis has attracted much attention. In this study, we successfully cloned four putative dTDP-l-rhamnose synthesis genes Ss-rmlABCD from Saccharothrix syringae CGMCC 4.1716 and expressed them in Escherichia coli. The recombinant enzymes, Ss-RmlA (glucose-1-phosphate thymidylyltransferase), Ss-RmlB (dTDP-d-glucose 4,6-dehydratase), Ss-RmlC (dTDP-4-keto-6-deoxy-glucose 3,5-epimerase), and Ss-RmlD (dTDP-4-keto-rhamnose reductase), were confirmed to catalyze the sequential formation of dTDP-l-rhamnose from deoxythymidine triphosphate (dTTP) and glucose-1-phosphate (Glc-1-P). Ss-RmlA showed maximal enzyme activity at 37°C and pH 9.0 with 2.5mMMg2+, and the K m and k cat values for dTTP and Glc-1-P were 49.56μM and 5.39s-1, and 117.30μM and 3.46s-1, respectively. Ss-RmlA was promiscuous in the substrate choice and it could use three nucleoside triphosphates (dTTP, dUTP, and UTP) and three sugar-1-Ps (Glc-1-P, GlcNH2-1-P, and GlcN3-1-P) to form nine sugar nucleotides (dTDP-GlcNH2, dTDP-GlcN3, UDP-Glc, UDP-GlcNH2, UDP-GlcN3, dUDP-Glc, dUDP-GlcNH2, and dUDP-GlcN3). Ss-RmlB showed maximal enzyme activity at 50°C and pH 7.5 with 0.02mM NAD+, and the K m and k cat values for dTDP-glucose were 98.60μM and 11.2s-1, respectively. A one-pot four-enzyme reaction system was developed by simultaneously mixing all of the substrates, reagents, and four enzymes Ss-RmlABCD in one pot for the synthesis of dTDP-l-rhamnose and dUDP-l-rhamnose with the maximal yield of 65% and 46%, respectively, under the optimal conditions. dUDP-l-rhamnose was a novel nucleotide-activated rhamnose reported for the first time.

Polymer Chemistry Applications of Cyrene and its Derivative Cygnet 0.0 as Safer Replacements for Polar Aprotic Solvents

This study explores a binary solvent system composed of biobased Cyrene and its derivative Cygnet 0.0 for application in membrane technology and in biocatalytic synthesis of polyesters. Cygnet-Cyrene blends could represent viable replacements for toxic polar aprotic solvents. The use of a 50 wt % Cygnet-Cyrene mixture makes a practical difference in the production of flat sheet membranes by nonsolvent-induced phase separation. New polymeric membranes from cellulose acetate, polysulfone, and polyimide are manufactured by using Cyrene, Cygnet 0.0, and their blend. The resultant membranes have different morphology when the solvent/mixture and temperature of the casting solution change. Moreover, Cyrene, Cygnet 0.0, and Cygnet-Cyrene are also explored for substituting diphenyl ether for the biocatalytic synthesis of polyesters. The results indicate that Cygnet 0.0 is a very promising candidate for the enzymatic synthesis of high molecular weight polyesters.

Immobilized Lipase Based on Hollow Mesoporous Silicon Spheres for Efficient Enzymatic Synthesis of Resveratrol Ester Derivatives

Enzymatic esterification of resveratrol is crucial for its potential application in lipophilic foods and drugs. However, the poor activity of the free enzyme hinders the reaction. In this work, the highly efficient enzymatic synthesis of resveratrol ester derivatives was achieved by immobilized lipase on hydrophobic modified hollow mesoporous silicon spheres (HMSS-C₈). We preliminarily explored the use of Candida sp. 99-125 lipase (CSL) for the acylation of resveratrol, with a regioselectivity toward 3-OH- over 4'-OH-acylation. HMSS-C₈ provided ideal accommodation for CSL with a loading capacity of up to 652 mg/g. The catalytic efficiency of CSL@HMSS-C₈ was 15 times higher than that of free CSL, and the conversion of resveratrol reached 98.7% within only 2 h, which is the fastest value recorded in the current literature. After 10 cycles, the conversion remained up to 86.3%. Benefiting from better lipid solubility, the relative oxidation stability index values of oil containing monoester derivatives were 43.1%-68.8% and 23.9%-33.2% higher than that of refined oil and oil containing resveratrol, respectively. This research provides a new pathway for efficient enzymatic synthesis of resveratrol ester derivatives and demonstrates the potential application of resveratrol monoester derivatives as a group of excellent lipid-soluble antioxidants.

Poly(butylene succinate-co-ε-caprolactone) Copolyesters: Enzymatic Synthesis in Bulk and Thermal Properties

This work explores for the first time the enzymatic synthesis of poly(butylene-co-ε-caprolactone) (PBSCL) copolyesters in bulk using commercially available monomers (dimethyl succinate (DMS), 1,4-butanediol (BD), and ε-caprolactone (CL)). A preliminary kinetic study was carried out which demonstrated the higher reactivity of DMS over CL in the condensation/ring opening polymerization reaction, catalyzed by Candida antarctica lipase B. PBSCL copolyesters were obtained with high molecular weights and a random microstructure, as determined by ¹³C NMR. They were thermally stable up to 300 °C, with thermal stability increasing with the content of CL in the copolyester. All of them were semicrystalline, with melting temperatures and enthalpies decreasing up to the eutectic point observed at intermediate compositions, and glass transition temperatures decreasing with the content of CL in the copolyester. The use of CALB provided copolyesters free from toxic metallic catalyst, which is very useful if the polymer is intended to be used for biomedical applications.

Enzymatic Synthesis and Structural Confirmation of Novel Oligosaccharide, D-Fructofuranose-linked Chitin Oligosaccharide

Utilizing transglycosylation reaction catalyzed by β- N -acetylhexosaminidase of Stenotrophomonas maltophilia , β-D-fructofuranosyl-(2↔1)-α- N , N ´diacetylchitobioside (GlcNAc ₂ -Fru) was synthesized from N -acetylsucrosamine and N , N ´-diacetylchitobiose (GlcNAc ₂ ), and β-D-fructofuranosyl-(2↔1)-α- N , N ´, N ´´-triacetylchitotrioside (GlcNAc ₃ -Fru) was synthesized from GlcNAc ₂ -Fru and GlcNAc ₂ . Through purification by charcoal column chromatography, pure GlcNAc ₂ -Fru and GlcNAc ₃ -Fru were obtained in molar yields of 33.0 % and 11.7 % from GlcNAc ₂ , respectively. The structures of these oligosaccharides were confirmed by comparing instrumental analysis data of fragments obtained by enzymatic hydrolysis and acid hydrolysis of them with known data of these fragments.

Enzymatic Synthesis of Chimeric DNA Oligonucleotides by in Vitro Transcription with dTTP, dCTP, dATP, and 2'-Fluoro Modified dGTP

Efficient ways to produce single-stranded DNA are of great interest for diverse applications in molecular biology and nanotechnology. In the present study, we selected T7 RNA polymerase mutants with reduced substrate specificity to employ an in vitro transcription reaction for the synthesis of chimeric DNA oligonucleotides, either individually or in pools. We performed in vitro evolution based on fluorescence-activated droplet sorting and identified mutations V783M, V783L, V689Q, and G555L as novel variants leading to relaxed substrate discrimination. Transcribed chimeric oligonucleotides were tested in PCR, and the quality of amplification products as well as fidelity of oligonucleotide synthesis were assessed by NGS. We concluded that enzymatically produced chimeric DNA transcripts contain significantly fewer deletions and insertions compared to chemically synthesized counterparts and can successfully serve as PCR primers, making the evolved enzymes superior for simple and cheap one-pot synthesis of multiple chimeric DNA oligonucleotides in parallel using a plethora of premixed templates.

Mix-and-Match System for the Enzymatic Synthesis of Enantiopure Glycerol-3-Phosphate-Containing Capsule Polymer Backbones from Actinobacillus pleuropneumoniae, Neisseria meningitidis, and Bibersteinia trehalosi

Capsule polymers are crucial virulence factors of pathogenic bacteria and are used as antigens in glycoconjugate vaccine formulations. Some Gram-negative pathogens express poly(glycosylglycerol phosphate) capsule polymers that resemble Gram-positive wall teichoic acids and are synthesized by TagF-like capsule polymerases. So far, the biotechnological use of these enzymes for vaccine developmental studies was restricted by the unavailability of enantiopure CDP-glycerol, one of the donor substrates required for polymer assembly. Here, we use CTP:glycerol-phosphate cytidylyltransferases (GCTs) and TagF-like polymerases to synthesize the poly(glycosylglycerol phosphate) capsule polymer backbones of the porcine pathogen Actinobacillus pleuropneumoniae, serotypes 3 and 7 (App3 and App7). GCT activity was confirmed by high-performance liquid chromatography, and polymers were analyzed using comprehensive nuclear magnetic resonance studies. Solid-phase synthesis protocols were established to allow potential scale-up of polymer production. In addition, one-pot reactions exploiting glycerol-kinase allowed us to start the reaction from inexpensive, widely available substrates. Finally, this study highlights that multidomain TagF-like polymerases can be transformed by mutagenesis of active site residues into single-action transferases, which in turn can act in trans to build-up structurally new polymers. Overall, our protocols provide enantiopure, nature-identical capsule polymer backbones from App2, App3, App7, App9, and App11, Neisseria meningitidis serogroup H, and Bibersteinia trehalosi serotypes T3 and T15. IMPORTANCE Economic synthesis platforms for the production of animal vaccines could help reduce the overuse and misuse of antibiotics in animal husbandry, which contributes greatly to the increase of antibiotic resistance. Here, we describe a highly versatile, easy-to-use mix-and-match toolbox for the generation of glycerol-phosphate-containing capsule polymers that can serve as antigens in glycoconjugate vaccines against Actinobacillus pleuropneumoniae and Bibersteinia trehalosi, two pathogens causing considerable economic loss in the swine, sheep, and cattle industries. We have established scalable protocols for the exploitation of a versatile enzymatic cascade with modular architecture, starting with the preparative-scale production of enantiopure CDP-glycerol, a precursor for a multitude of bacterial surface structures. Thereby, our approach not only allows the synthesis of capsule polymers but might also be exploitable for the (chemo)enzymatic synthesis of other glycerol-phosphate-containing structures such as Gram-positive wall teichoic acids or lipoteichoic acids.

A Bi-Enzymatic Cascade Pathway towards Optically Pure FAHFAs*

Recently discovered endogenous mammalian lipids, fatty acid esters of hydroxy fatty acids (FAHFAs), have been proved to have anti-inflammatory and anti-diabetic effects. Due to their extremely low abundancies in vivo, forging a feasible scenario for FAHFA synthesis is critical for their use in uncovering biological mechanisms or in clinical trials. Here, we showcase a fully enzymatic approach, a novel in vitro bi-enzymatic cascade system, enabling an effective conversion of nature-abundant fatty acids into FAHFAs. Two hydratases from Lactobacillus acidophilus were used for converting unsaturated fatty acids to various enantiomeric hydroxy fatty acids, followed by esterification with another fatty acid catalyzed by Candida antarctica lipase A (CALA). Various FAHFAs were synthesized in a semi-preparative scale using this bi-enzymatic approach in a one-pot two-step operation mode. In all, we demonstrate that the hydratase-CALA system offers a promising route for the synthesis of optically pure structure-diverse FAHFAs.

Biotechnological Production of 2'-Fucosyllactose: A Prevalent Fucosylated Human Milk Oligosaccharide

Human milk oligosaccharide (HMO) is a key component of human milk carbohydrates and is closely related to the nutrition and health benefits of breastfeeding in infants. 2'-Fucosyllactose (2'-FL) is the most abundant fucosylated HMO, which has remarkable value in nutrition and medicine, such as suppressing pathogen infection, regulating intestinal flora, and boosting immunity. However, 2'-FL production via the method of extraction or chemical synthesis cannot meet its large demand, and as a result, environmentally friendly and efficient biotechnological approaches, including in vitro enzymatic synthesis and microbial cell factory production, have been developed and applied to its commercialized production. This review introduces, summarizes, and discusses the recent advances in the biotechnological production of 2'-FL. Furthermore, future research directions for the biotechnological production of 2'-FL as well as the strategies to further improve its concentration are highlighted and discussed.

Polymer Networks Synthesized from Poly(Sorbitol Adipate) and Functionalized Poly(Ethylene Glycol)

Polymer networks were prepared by Steglich esterification using poly(sorbitol adipate) (PSA) and poly(sorbitol adipate)-graft-poly(ethylene glycol) mono methyl ether (PSA-g-mPEG12) copolymer. Utilizing multi-hydroxyl functionalities of PSA, poly(ethylene glycol) (PEG) was first grafted onto a PSA backbone. Then the cross-linking of PSA or PSA-g-mPEG12 was carried out with disuccinyl PEG of different molar masses (Suc-PEGn-Suc). Polymers were characterized through nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The degree of swelling of networks was investigated through water (D2O) uptake studies, while for detailed examination of their structural dynamics, networks were studied using 13C magic angle spinning NMR (13C MAS NMR) spectroscopy, 1H double quantum NMR (1H DQ NMR) spectroscopy, and 1H pulsed field gradient NMR (1H PFG NMR) spectroscopy. These solid state NMR results revealed that the networks were composed of a two component structure, having different dipolar coupling constants. The diffusion of solvent molecules depended on the degree of swelling that was imparted to the network by the varying chain length of the PEG based cross-linking agent.

[Characterization of inulosucrase and the enzymatic synthesis of inulin]

As a type of prebiotics and dietary fiber, inulin performs plenty of significant physiological functions and is applied in food and pharmaceutical fields. Inulosucrase from microorganisms can use sucrose as the substrate to synthesize inulin possessing higher molecular weight than that from plants. In this work, a hypothetical gene coding inulosucrase was selected from the GenBank database. The catalytic domain was remained by N- and C- truncation strategies, constructing the recombinant plasmid. The recombinant plasmid was expressed in E. coli expression system, and after purifying the crude enzyme by Ni²⁺ affinity chromatography, a recombinant enzyme with a molecular weight of approximately 65 kDa was obtained. The optimal pH and temperature of the recombinant enzyme were 5.5 and 45 °C, respectively, when sucrose was used as the sole substrate. The activity of this enzyme was inhibited by various metal ions at different degrees. After purifying the produced polysaccharide, nuclear magnetic resonance analysis was used to determine that the polysaccharide was inulin connected by β-(2,1) linkages. Finally, the conditions for the production of inulin were optimized. The results showed that the inulin production reached the maximum, approximately 287 g/L after 7 h, when sucrose concentration and enzyme dosage were 700 g/L and 4 U/mL, respectively. The conversion rate from sucrose to inulin was approximately 41%.

One-pot enzymatic synthesis of 2-deoxy-scyllo-inosose from d-glucose and polyphosphate

2-Deoxy-scyllo-inosose (2DOI, [2S,3R,4S,5R]-2,3,4,5-tetrahydroxycyclohexan-1-one) is a biosynthetic intermediate of 2-deoxystreptamine-containing aminoglycoside antibiotics, including butirosin, kanamycin, and neomycin. In producer microorganisms, 2DOI is constructed from d-glucose 6-phosphate (G6P) by 2-deoxy-scyllo-inosose synthase (DOIS) with the oxidized form of nicotinamide adenine dinucleotide (NAD+). 2DOI is also known as a sustainable biomaterial for production of aromatic compounds and a chiral cyclohexane synthon. In this study, a one-pot enzymatic synthesis of 2DOI from d-glucose and polyphosphate was investigated. First, 3 polyphosphate glucokinases (PPGKs) were examined to produce G6P from d-glucose and polyphosphate. A PPGK derived from Corynebacterium glutamicum (cgPPGK) was found to be suitable for G6P production under ordinary enzymatic conditions. Next, 7 DOISs were examined for the one-pot enzymatic reaction. As a result, cgPPGK and BtrC, the latter of which is a DOIS derived from the butirosin producer Bacillus circulans, achieved nearly full conversion of d-glucose to 2DOI in the presence of polyphosphate.

Synthesis of selected unnatural sugar nucleotides for biotechnological applications

Sugar nucleotides are the principal building blocks for the synthesis of most complex carbohydrates and are crucial intermediates in carbohydrate metabolism. Uridine diphosphate (UDP) monosaccharides are among the most common sugar nucleotide donors and are transferred to glycosyl acceptors by glycosyltransferases or synthases in glycan biosynthetic pathways. These natural nucleotide donors have great biological importance, however, the synthesis and application of unnatural sugar nucleotides that are not available from in vivo biosynthesis are not well explored. In this review, we summarize the progress in the preparation of unnatural sugar nucleotides, in particular, the widely studied UDP-GlcNAc/GalNAc analogs. We focus on the "two-block" synthetic pathway that is initiated from monosaccharides, in which the first block is the synthesis of sugar-1-phosphate and the second block is the diphosphate bond formation. The biotechnological applications of these unnatural sugar nucleotides showing their physiological and pharmacological potential are discussed.

The application of L-glutaminase for the synthesis of the immunomodulatory γ-D-glutamyl-L-tryptophan and the kokumi-imparting γ-D-glutamyl peptides

Glutaminase of Bacillus amyloliquefaciens has been used to synthesize the immunomodulatory γ-D-glutamyl-L-tryptophan (γ-D-Glu-L-Trp) and the kokumi-active γ-D-glutamyl peptides. The optimum yield of γ-D-Glu-L-Trp was 55.76 mM in corresponding to a minimum yield of by-product (γ-D-Glu-γ-D-Glu-L-Trp) in the presence of 75 mM D-Gln and 100 mM L-Trp. The glutaminase has a low Km values for the donors (D-Gln and L-Gln:5.53 and 0.98 mM), but high ones for the acceptors (L-Trp, L-Phe, L-Met, L-Val and γ-[D-Glu]( n =1,2,3)-L-Val/L-Phe/L-Met, ranging from 32.51 to 193.05 mM). The highest Km value appearing when n = 2 (γ-[D-Glu]( n =0,1,2)-L-Val/L-Phe/L-Met) suggested the rising difficulty for synthesis when the number of donor increases in the reaction mixtures. The γ-[D-Glu]( n =1,2,3)-L-Val/L-Phe/L-Met at 5 mM can impart the blank chicken broth an enhancing monthfulness, thickness, and umaminess taste.

Acid Treatment Enhances the Antioxidant Activity of Enzymatically Synthesized Phenolic Polymers

Phenolic polymers produced by enzymatic oxidation under biomimetic and eco-friendly reaction conditions are usually endowed with potent antioxidant properties. These properties, coupled with the higher biocompatibility, stability and processability compared to low-molecular weight phenolic compounds, open important perspectives for various applications. Herein, we report the marked boosting effect of acid treatment on the antioxidant properties of a series of polymers obtained by peroxidase-catalyzed oxidation of natural phenolic compounds. Both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays indicated a remarkable increase in the antioxidant properties for most phenolic polymers further to the acid treatment. In particular, up to a ca. 60% decrease in the EC50 value in the DPPH assay and a 5-fold increase in the Trolox equivalents were observed. Nitric oxide- and superoxide-scavenging assays also indicated highly specific boosting effects of the acid treatment. Spectroscopic evidence suggested, in most cases, that the occurrence of structural modifications induced by the acid treatment led to more extended π-electron-conjugated species endowed with more efficient electron transfer properties. These results open new perspectives toward the design of new bioinspired antioxidants for application in food, biomedicine and material sciences.

Cell-Free Synthesis of Dopamine and Serotonin in Two Steps with Purified Enzymes

The synthesis of serotonin and dopamine with purified enzymes is described. Both pathways start from an amino acid substrate and synthesize the monoamine neurotransmitter in two enzymatic steps. The enzymes human tryptophan hydroxylase isoform 2, Rattus norvegicus tyrosine hydroxylase, Chlamydia pneumoniae Cpn1046, and aromatic amino acid decarboxylase from Drosophila melanogaster are recombinantly expressed, purified, and shown to be functional in vitro. The hydroxylases efficiently convert L-DOPA (L-dihydroxy-phenylalanine) and 5-HTP (5-hydroxytryptophan) from L-tyrosine and L-tryptophan, respectively. A single aromatic amino acid decarboxylase is capable of converting both hydroxylated intermediates into the final neurotransmitter. The platform described here may facilitate future efforts to generate medically useful artificial cells and nanofactories.

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS^- in aqueous solutions of Cd-acetate and graphene oxide, respectively. Exchange of cysteamine for the native l-cysteine ligand capping the CdS QDs drives self-assembly of the now positively charged cysteamine-capped CdS (CdS/CA) onto negatively charged rGO. The use of this short linker molecule additionally enables efficient charge transfer from CdS to rGO, increasing exciton lifetime and, subsequently, photocatalytic activity. The visible-light hydrogen evolution rate of the resulting CdS/CA/rGO photocatalyst is 3300 μmol h^-1 g^-1. This represents, to our knowledge, one of the highest reported rates for a CdS/rGO nanocomposite photocatalyst, irrespective of the synthesis method.

Kinetics of Enzymatic Synthesis of Cyanidin-3-Glucoside Lauryl Ester and Its Physicochemical Property and Proliferative Effect on Intestinal Probiotics

The interest in anthocyanins used in food, cosmetic, and pharmaceutical industries has increased the research in order to improve their stability while maintaining bioactivity. In this work, cyanidin-3-glucoside lauryl ester (Cy3glc-C12) was enzymatically synthesized, using Novozym 435 as a catalyst, as well as to obtain a kinetic model for the bioprocess. Its liposolubility, UV–VIS absorbance property, thermostability, and potential proliferative effect on intestinal probiotics were also studied. The maximum conversion yield (68.7 ± 2.1%) was obtained with a molar ratio (substrate:donor) of 1:56, 435 16.5 g/L Novozym, temperature of 56 °C, and a time of 28 h via the acylation occurred at 6′′-OH position of the glucoside. The kinetics of the reaction is consistent with a ping-pong bi-bi mechanism and the parameters of the respective kinetic equations are reported. Compared with native Cy3glc, the liposolubility, pH resistivity and thermostability of Cy3glc-C12 were significantly improved. The growth kinetics of Bifidobacteria and Lactobacillus was established based on the Logistic equation, and Cy3glc-C12 could promote their proliferation especially during the logarithmic growth, in which lower pH and more bacteria population were found compared with those of media without anthocyanins. This research provided a reference for the industrial production of Cy3glc-C12 and extended its application to natural products in lipophilic systems.

Hypoxanthine-Guanine Phosphoribosyltransferase/adenylate Kinase From Zobellia galactanivorans: A Bifunctional Catalyst for the Synthesis of Nucleoside-5'-Mono-, Di- and Triphosphates

In our search for novel biocatalysts for the synthesis of nucleic acid derivatives, we found a good candidate in a putative dual-domain hypoxanthine-guanine phosphoribosyltransferase (HGPRT)/adenylate kinase (AMPK) from Zobellia galactanivorans (ZgHGPRT/AMPK). In this respect, we report for the first time the recombinant expression, production, and characterization of a bifunctional HGPRT/AMPK. Biochemical characterization of the recombinant protein indicates that the enzyme is a homodimer, with high activity in the pH range 6-7 and in a temperature interval from 30 to 80°C. Thermal denaturation experiments revealed that ZgHGPRT/AMPK exhibits an apparent unfolding temperature (Tm) of 45°C and a retained activity of around 80% when incubated at 40°C for 240 min. This bifunctional enzyme shows a dependence on divalent cations, with a remarkable preference for Mg²⁺ and Co²⁺ as cofactors. More interestingly, substrate specificity studies revealed ZgHGPRT/AMPK as a bifunctional enzyme, which acts as phosphoribosyltransferase or adenylate kinase depending upon the nature of the substrate. Finally, to assess the potential of ZgHGPRT/AMPK as biocatalyst for the synthesis of nucleoside-5′-mono, di- and triphosphates, the kinetic analysis of both activities (phosphoribosyltransferase and adenylate kinase) and the effect of water-miscible solvents on enzyme activity were studied.

Enzymatic Synthesis of Glucose Monodecanoate in a Hydrophobic Deep Eutectic Solvent

Environmentally friendly and biodegradable reaction media are an important part of a sustainable glycolipid production in the transition to green chemistry. Deep eutectic solvents (DESs) are an ecofriendly alternative to organic solvents. So far, only hydrophilic DESs were considered for enzymatic glycolipid synthesis. In this study, a hydrophobic DES consisting of (-)-menthol and decanoic acid is presented for the first time as an alternative to hydrophilic DES. The yields in the newly introduced hydrophobic DES are significantly higher than in hydrophilic DESs. Different reaction parameters were investigated to optimize the synthesis further. Twenty milligrams per milliliter iCalB and 0.5 M glucose resulted in the highest initial reaction velocity for the esterification reaction, while the highest initial reaction velocity was achieved with 1.5 M glucose in the transesterification reaction. The enzyme was proven to be reusable for at least five cycles without significant loss of activity.

Development of 6'-N-Acylated Isepamicin Analogs with Improved Antibacterial Activity Against Isepamicin-Resistant Pathogens

The development of new aminoglycoside (AG) antibiotics has been required to overcome the resistance mechanism of AG-modifying enzymes (AMEs) of AG-resistant pathogens. The AG acetyltransferase, AAC(6′)-APH(2″), one of the most typical AMEs, exhibiting substrate promiscuity towards a variety of AGs and acyl-CoAs, was employed to enzymatically synthesize new 6′-N-acylated isepamicin (ISP) analogs, 6′-N-acetyl/-propionyl/-malonyl ISPs. They were all active against the ISP-resistant Gram-negative bacteria tested, and the 6′-N-acetyl ISP displayed reduced toxicity compared to ISP in vitro. This study demonstrated the importance of the modification of the 6′-amino group in circumventing AG-resistance and the potential of regioselective enzymatic modification of AG scaffolds for the development of more robust AG antibiotics.

Optimization of Glycolipid Synthesis in Hydrophilic Deep Eutectic Solvents

Glycolipids are considered an alternative to petrochemically based surfactants because they are non-toxic, biodegradable, and less harmful to the environment while having comparable surface-active properties. They can be produced chemically or enzymatically in organic solvents or in deep eutectic solvents (DES) from renewable resources. DES are non-flammable, non-volatile, biodegradable, and almost non-toxic. Unlike organic solvents, sugars are easily soluble in hydrophilic DES. However, DES are highly viscous systems and restricted mass transfer is likely to be a major limiting factor for their application. Limiting factors for glycolipid synthesis in DES are not generally well understood. Therefore, the influence of external mass transfer, fatty acid concentration, and distribution on initial reaction velocity in two hydrophilic DES (choline:urea and choline:glucose) was investigated. At agitation speeds of and higher than 60 rpm, the viscosity of both DES did not limit external mass transfer. Fatty acid concentration of 0.5 M resulted in highest initial reaction velocity while higher concentrations had negative effects. Fatty acid accessibility was identified as a limiting factor for glycolipid synthesis in hydrophilic DES. Mean droplet sizes of fatty acid-DES emulsions can be significantly decreased by ultrasonic pretreatment resulting in significantly increased initial reaction velocity and yield (from 0.15 ± 0.03 μmol glucose monodecanoate/g DES to 0.57 ± 0.03 μmol/g) in the choline: urea DES. The study clearly indicates that fatty acid accessibility is a limiting factor in enzymatic glycolipid synthesis in DES. Furthermore, it was shown that physical pretreatment of fatty acid-DES emulsions is mandatory to improve the availability of fatty acids.