One-pot Twostep Chemobiocatalytic Synthesis of a Furan Amino Acid from 5-Hydroxymethylfurfural

Recently, catalytic valorization of biomass-derived furans has received growing interest. 5-Aminomethyl-2-furancarboxylic acid (AMFC), a furan amino acid, holds great promise in the aeras of polymer and pharmaceutical, but its synthesis remains limited. In this work, we report a chemobiocatalytic route toward AMFC by combining laccase-TEMPO system and recombinant Escherichia coli (named E. coli_TAF) harboring ω-transaminase (TA), L-alanine dehydrogenase (L-AlaDH) and formate dehydrogenase (FDH), starting from 5-hydroxymethylfurfural (HMF). In the cascade, HMF is oxidized into 5-formyl-2-furancarboxylic acid (FFCA) by laccase-TEMPO system, and then the resulting intermediate is converted into AMFC by E. coli_TAF via transamination with cheap ammonium formate instead of costly organic amine donors, theoretically generating H2O and CO2 as by-products. The tandem process was run in a one-pot twostep manner, affording AMFC with approximately 81 % yield, together with 10 % 2,5-furandicarboxylic acid (FDCA) as by-product. In addition, the scale-up production of AMFC was demonstrated, with 0.41 g/L h productivity and 8.6 g/L titer. This work may pave the way for green manufacturing of the furan-containing amino acid.

Fabrication of multifunctional ethyl cellulose/gelatin-based composite nanofilm for the pork preservation and freshness monitoring

In this study, an active and intelligent nanofilm for monitoring and maintaining the freshness of pork was developed using ethyl cellulose/gelatin matrix through electrospinning, with the addition of natural purple sweet potato anthocyanin. The nanofilm exhibited discernible color variations in response to pH changes, and it demonstrated a higher sensitivity towards volatile ammonia compared with casting film. Notably, the experimental findings regarding the wettability and pH response performance indicated that the water contact angle between 70° and 85° was more favorable for the smart response of pH sensitivity. Furthermore, the film exhibited desirable antioxidant activities, water vapor barrier properties and also good antimicrobial activities with the incorporation of ε-polylysine, suggesting the potential as a food packaging film. Furthermore, the application preservation outcomes revealed that the pork packed with the nanofilm can prolong shelf life to 6 days, more importantly, a distinct color change aligned closely with the points indicating the deterioration of the pork was observed, changing from light pink (indicating freshness) to light brown (indicating secondary freshness) and then to brownish green (indicating spoilage). Hence, the application of this multifunctional film in intelligent packaging holds great potential for both real-time indication and efficient preservation of the freshness of animal-derived food items.

Structural and interfacial properties of acetylated Millettia speciosa Champ polysaccharide and stability evaluation of the resultant O/W emulsion containing β-carotene

The aim of this study was to investigate the effects of acetylation modification on the structural, interfacial and emulsifying properties of Millettia speciosa Champ polysaccharide (MSCP). Besides, the influence of acetylation modification on the encapsulation properties of polysaccharide-based emulsion was also explored. Results indicated that modification resulted in a prominent reduction in molecular weight of MSCP and the interfacial layer thickness formed by acetylated MSCP (AC-MSCP) was also decreased, but the adsorption rate and ability of AC-MSCP to reduce interfacial tension were improved. AC-MSCP formulated emulsion possessed smaller droplet size (6.8 μm) and exhibited better physical stability under stressful conditions. The chemical stability of β-carotene was also profoundly enhanced by AC-MSCP fabricated emulsion. Moreover, AC-MSCP improved lipids digestion extent, thus facilitating the formation of micelle and increasing bioaccessibility of β-carotene. This study provided insights for rational modification of polysaccharide-based emulsifier and designing delivery system for chemically labile hydrophobic bioactive components.

Novel Multitarget ACE Inhibitory Peptides from Bovine Colostrum Immunoglobulin G: Cellular Transport, Efficacy in Regulating Endothelial Dysfunction, and Network Pharmacology Studies

In this study, we used traditional laboratory methods, bioinformatics, and cellular models to screen novel ACE inhibitory (ACEI) peptides with strong ACEI activity, moderate absorption rates, and multiple targets from bovine colostrum immunoglobulin G (IgG). The purified fraction of the compound proteinase hydrolysate of IgG showed good ACEI activity. After nano-UPLC-MS/MS identification and in silico analysis, eight peptides were synthesized and verified. Among them, SFYPDY, TSFYPDY, FSWF, WYQQVPGSGL, and GVHTFP were identified as ACEI peptides, as they exhibited strong ACEI activity (with IC50 values of 104.7, 80.0, 121.2, 39.8, and 86.3 μM, respectively). They displayed good stability in an in vitro simulated gastrointestinal digestion assay. In a Caco-2 monolayer model, SFYPDY, FSWF, and WYQQVPGSGL exhibited better absorption rates and lower IC50 values than the other peptides and were thereby identified as novel ACEI peptides. Subsequently, in a H2O2-induced endothelial dysfunction (ED) model based on HUVECs, SFYPDY, FSWF, and WYQQVPGSGL regulated ED by reducing apoptosis and ROS accumulation while upregulating NOS3 mRNA expression. Network pharmacology analysis and RT-qPCR confirmed that they regulated multiple targets. Overall, our results suggest that SFYPDY, FSWF, and WYQQVPGSGL can serve as novel multitarget ACEI peptides.

A dual-mode sensing platform based on metal-organic framework for colorimetric and ratiometric fluorescent detection of organophosphorus pesticide

Pesticide residues have raised considerable concern about environmental health and food safety. Despite a great advance in enzymatic sensors for pesticide detection, the intrinsic fragility of native enzyme and possible fake results due to single mode signal have hindered its wide application. Here, a novel dual-mode sensor is reported for organophosphorus pesticide detection by using metal-organic framework (MOF) nanozyme NH2-CuBDC as sensing element. The intrinsic peroxidase-mimicking activity and fluorescence property of NH2-CuBDC enable both colorimetric and fluorescent detection of chlorpyrifos. Compared with previously reported chlorpyrifos sensors, our sensor exhibits outstanding sensitivity, and the limits of detection (LOD, S/N = 3) in colorimetric and fluorescent modes are 1.57 ng/mL and 2.33 ng/mL, respectively. No obvious interferences from other substances were measured and chlorpyrifos analysis in real samples presented good reliability, showing practical potential. This work is anticipated to provide new insights to develop multifunctional nanozymes and integrated multi-mode sensing platforms.

Iron-incorporated metal-organic frameworks for oxidative cleavage of trans-anethole to p-anisaldehyde

An iron-incorporated Zn-MOF catalyst Zn-bpydc·Fe was fabricated for the oxidative cleavage of trans-anethole to p-anisaldehyde under facile conditions, under 1 atm of O2. The Fe coordinated bipyridine serves as the catalytically active center inside the structural skeleton of Zn-MOFs. This work affords a new avenue for the mild oxidation of olefins.

Improving the bioaccessibility of lipophilic ingredient in its oral intestinal delivery by ultrasound and biological cross-linker

BACKGROUND

Great efforts have been made to improve the oral bioaccessibility of lipophilic ingredients with multi-functionalities. Achieving intestinal delivery of lipophilic ingredients and their encapsulation in micelles composed of bile salts and lipid hydrolysates (i.e. fatty acids) is critical for improving oral bioaccessibility. Therefore, oil-core microcapsules are considered ideal carriers of lipophilic ingredients. Previous studies have reported oil-core/zein-shell microcapsules constructed by a one-step anti-solvent process. Still, its efficacy as an intestinal delivery system was limited because if the porous shell structure.

RESULTS

Zein solution was pretreated with ultrasound and tannic acid (TA) cross-linking. Composite oil-core microcapsule (COM) with a compact shell structure was successfully prepared by using modified zein solution in the anti-solvent process. Fourier-transform infrared spectroscopy and circular dichroism analyses indicated that ultrasound and TA synergistically promote the conformational transition of zein from α-helix to β-sheet and enhance the hydrophobic interactions among protein chains. The above changes contribute to the strengthen of shell zein network. Correspondingly, COM presents superior encapsulation efficiency and environmental stability over the simple oil-core microcapsule (SOM) prepared without the use of ultrasound and TA. Furthermore, antioxidant activity of β-carotene was well retained during the encapsulation process. In vitro studies indicated that COM was more resistant to digestibility and acid-induced swelling. More than 87% of β-carotene could be released in the intestine in a sustainable way. The controllable release behavior thus promoted a significant increase in bioaccessibility of β-carotene encapsulated in COM compared to SOM (85.9% versus 48.5%).

CONCLUSION

The COM generated here shows potential for bioaccessibility improvement of lipophilic ingredients. © 2022 Society of Chemical Industry.

1,4-α-Glucosidase from Fusarium solani for Controllable Biosynthesis of Silver Nanoparticles and Their Multifunctional Applications

In the study, monodispersed silver nanoparticles (AgNPs) with an average diameter of 9.57 nm were efficiently and controllably biosynthesized by a reductase from Fusarium solani DO7 only in the presence of β-NADPH and polyvinyl pyrrolidone (PVP). The reductase responsible for AgNP formation in F. solani DO7 was further confirmed as 1,4-α-glucosidase. Meanwhile, based on the debate on the antibacterial mechanism of AgNPs, this study elucidated in further depth that antibacterial action of AgNPs was achieved by absorbing to the cell membrane and destabilizing the membrane, leading to cell death. Moreover, AgNPs could accelerate the catalytic reaction of 4-nitroaniline, and 86.9% of 4-nitroaniline was converted to p-phenylene diamine in only 20 min by AgNPs of controllable size and morphology. Our study highlights a simple, green, and cost-effective process for biosynthesizing AgNPs with uniform sizes and excellent antibacterial activity and catalytic reduction of 4-nitroaniline.

Purification, structural elucidation and biological activities of exopolysaccharide produced by the endophytic Penicillium javanicum from Millettia speciosa Champ

An acid polysaccharide, named HP, was produced by endophytic Penicillium javanicum MSC-R1 isolated from southern medicine Millettia speciosa Champ. The molecular weight of HP was 37.8 kDa and consisted of Ara f, Galр, Glcр, Manр, and GlcрA with a molar ratio of 1.09: 3.47: 68.48: 16.59: 8.85. The glycosidic linkage of HP was proven to be →3, 4)-α-D-Glcр-(1→6)-α-D-Manр-(1→, →3, 4)-α-D-Glcр-(1→4)-α-D-Glcр-(1→, →3), →6)-α-D-Manр-(1→4)-α-D-Glcр-(1→, →3), β-D-Galр-(1→3)-α-D-Glcр-(1→, →4), →5)-α-L-Ara f -(1→3)-α-D-Glcр-(1→, →4), →6)-α-D-Manр-(1→4)-α-D-GlcAр-(1→ and →4)-α-D-GlcAр-(1→4)-α-D-Glcр-(1→, →3). Additionally, 250 μg/mL of HP possessed nontoxicity to RAW 264.7 cells and exhibited anti-inflammation activity. HP could significantly restrain the amount of tumor necrosis factor-α, interleukin-6 and NO release in RAW264.7, which property is possibly associated with its abundant glucosidic linkage. These results indicated that HP could be regarded as a ponderable ingredient for the health-beneficial functional foods.

Extraction and characterization of a functional protein from Millettia speciosa Champ. leaf

Natural plant-derived protein with excellent bioactivities has attracted much attention so a functional protein with molecular weight of 15.2 kDa was extracted from Millettia speciosa Champ. leaf for the first time. Under the pH of 12.0, solid-liquid ratio of 1:40 (w/v), extraction time of 2.0 h, and extraction temperature of 50 °C, the highest extracting efficiency (79.25 ± 0.78%) of the Millettia speciosa Champ. leaf protein (MLP) was achieved. The main structure of MLP contained β-fold and β-corner by Fourier transform infrared spectroscopy (FTIR) and Circular dichroism (CD) spectra analysis. Additionally, MLP was predominant with glutamic acid, aspartic acid, and leucine, which could be considered as a high quality natural protein. MLP showed great water holding capacity (WHC), oil absorption capacity (OAC), as well as emulsifying and foaming properties. Simultaneously, MLP exhibited considerable antioxidant activity. These results suggested that MLP could be utilised as a promising ingredient of functional foods.

Construction of Zn-heptapeptide bionanozymes with intrinsic hydrolase-like activity for degradation of di(2-ethylhexyl) phthalate

Nanozyme with intrinsic enzyme-like activity has emerged as favorite artificial catalyst during recent years. However, current nanozymes are mainly limited to inorganic-derived nanomaterials, while biomolecule-sourced nanozyme (bionanozyme) are rarely reported. Herein, inspired by the basic structure of natural hydrolase family, we constructed 3 oligopeptide-based bionanozymes with intrinsic hydrolase-like activity by implementing zinc induced self-assembly of histidine-rich heptapeptides. Under mild condition, divalent zinc (Zn²⁺) impelled the spontaneous assembly of short peptides (i.e. Ac-IHIHIQI-CONH₂, Ac-IHIHIYI-CONH₂, and Ac-IHVHLQI-CONH₂), forming hydrolase-mimicking bionanozymes with β-sheet secondary conformation and nanofibrous architecture. As expected, the resultant bionanozymes were able to hydrolyze a serious of p-nitrophenyl esters, including not only the simple substrate with short side-chain (p-NPA), but also more complicated ones (p-NPB, p-NPH, p-NPO, and p-NPS). Moreover, the self-assembled Zn-heptapeptide bionanozymes were also proven to be capable of degrading di(2-ethylhexyl) phthalate (DEHP), a typical plasticizer, showing great potential for environmental remediation. Based on this study, we aim to provide theoretical references and exemplify a specific case for directing the construction and application of bionanozyme.

Enhancement of thermostability and catalytic properties of ammonia lyase through disulfide bond construction and backbone cyclization

Ammonia lyases have great application potential in food and pharmaceuticals owing to their unique ammonia addition reaction and atom economy. A novel methylaspartate ammonia-lyase, EcMAL, from E. coli O157:H7 showed high catalytic activity. To further strengthen its thermostability and activity, disulfide bond and backbone cyclization (cyclase) variants were constructed by rational design, respectively. Among them, variant M3, with a disulfide bond introduced, exhibited a 2.3-fold increase in half-life at 50 °C, while cyclase variant M8 showed better performance, with 25.9-fold increases. The synergistic promotion effect of this combinational strategy on activity and stability was also investigated, and the combined mutant M9 exhibited a 1.1-fold improvement in catalytic efficiency while maintaining good thermostability. Circular dichroism analysis and molecular dynamics simulation confirmed that the main sources of improved thermostability were reduced atomic fluctuation and a more stable secondary structure. To our knowledge, this is the first example of combining the introduction of disulfide bonds with cyclase construction to improve enzyme stability, which was characterized by modification away from the enzyme active center, and provided a new method for adjusting enzyme thermostability.

Development of Millettia speciosa champ polysaccharide conjugate stabilized oil-in-water emulsion for oral delivery of β-carotene: Protection effect and in vitro digestion fate

In this study, a natural antioxidant emulsifier, Millettia speciosa Champ polysaccharide conjugates (MSC-PC), was used for fabricating oil-in-water emulsion, and the influences of MSC-PC on β-carotene stability and bioaccessibility were studied. Results suggested that MSC-PC stabilized emulsion exhibited excellent resistance to a wide range of salt levels (0-500 mM of Na⁺), thermal treatments (50-90 °C) and pH values (3.0-11.0). MSC-PC also exhibited an outstanding inhibition capacity on lipid oxidation. Besides, MSC-PC stabilized emulsion had a better protective effect on β-carotene than other systems. Interestingly, in spite of similar lipolysis extent, β-carotene bioaccessibility in MSC-PC fabricated emulsion (14.75 %) was markedly higher than that in commercial Tween 80 fabricated emulsion (10.08 %), likely due to the steric-hindrance effect and antioxidant ability of MSC-PC, building interfacial layers that prevented β-carotene from degradation. This work supplied a deep insight into elucidating the mechanisms of emulsifying performance and β-carotene protection effect of MSC-PC fabricated emulsion.

Electrospinning of PLA Nanofibers: Recent Advances and Its Potential Application for Food Packaging

Poly(lactic acid), also abbreviated as PLA, is a promising biopolymer for food packaging owing to its environmental-friendly characteristic and desirable physical properties. Electrospinning technology makes the production of PLA-based nanomaterials available with expected structures and enhanced barrier, mechanical, and thermal properties; especially, the facile process produces a high encapsulation efficiency and controlled release of bioactive agents for the purpose of extending the shelf life and promoting the quality of foodstuffs. In this study, different types of electrospinning techniques used for the preparation of PLA-based nanofibers are summarized, and the enhanced properties of which are also described. Moreover, its application in active and intelligent packaging materials by introducing different components into nanofibers is highlighted. In all, the review establishes the promising prospects of PLA-based nanocomposites for food packaging application.

[Effect of enhanced recovery after surgery on surgical stress response in patients with gastric cancer complicated with type 2 diabetes mellitus]

Objective: To investigate the effect of enhanced recovery after surgery on the stress response of gastric cancer patients complicated with type 2 diabetes mellitus. Methods: We retrospectively analyzed the data of 49 patients with type 2 diabetes who underwent radical gastrectomy for gastric cancer in the Department of gastroenterology of the Affiliated Hospital of Jiangsu University from Jan to Dec 2020. They were randomly divided into experimental group and control group according to different perioperative management measures. The perioperative C-reactive protein (CRP), white blood cell (WBC), interleukin-6(IL-6), insulin resistance (HOMA-IR), blood glucose fluctuation and postoperative recovery were compared between the two groups. Results: A total of 49 patients were enrolled in the study (23 in the experimental group and 26 in the control group). The degree of stress reaction of the experimental group was lighter than that of the control group. The levels of CRP were significantly different on the 5th and 7th day after operation, IL-6 was significantly different on the 1st, 3rd, 5th and 7th day after operation, WBC and HOMA-IR were significantly different on the 1st day postoperatively. And the changes of HOMA-IR and blood glucose in experimental group were more gentle than those in control group. All the differences were statistically significant(P<0.05). In the experimental group, the time of first anal exhaust, indwelling time of drainage tube or nasointestinal tube and the total hospitalization time were significantly shorter than those of the control group(P<0.05). Conclusion: ERAS can reduce the degree of inflammatory stress and the postoperative IR level promote the early recovery of patients with gastric cancer complicated with type 2 diabetes mellitus.

Bifidobacterium spp. as functional foods: A review of current status, challenges, and strategies

Members of Bifidobacterium are among the first microbes to colonize the human intestine naturally, their abundance and diversity in the colon are closely related to host health. Recently, the gut microbiota has been gradually proven to be crucial mediators of various metabolic processes between the external environment and the host. Therefore, the health-promoting benefits of Bifidobacterium spp. and their applications in food have gradually been widely concerned. The main purpose of this review is to comprehensively introduce general features, colonization methods, and safety of Bifidobacterium spp. in the human gut, highlighting its health benefits and industrial applications. On this basis, the existing limitations and scope for future research are also discussed. Bifidobacteria have beneficial effects on the host's digestive system, immune system, and nervous system. However, the first prerequisite for functioning is to have enough live bacteria before consumption and successfully colonize the colon after ingestion. At present, strain breeding, optimization (e.g., selecting acid and bile resistant strains, adaptive evolution, high cell density culture), and external protection technology (e.g., microencapsulation and protectants) are the main strategies to address these challenges in food application.

Novel Antioxidative Wall Materials for Lactobacillus casei Microencapsulation via the Maillard Reaction between the Soy Protein Isolate and Prebiotic Oligosaccharides

In this study, three kinds of Maillard reaction products (MRPs) have been, for the first time, successfully prepared by conjugating soy protein isolate (SPI) with isomaltooligosaccharide, xylooligosaccharide, or galactooligosaccharide at 80 °C for 30 or 60 min and applied for the construction of Lactobacillus casei (L. casei) microcapsules. The results showed that MRPs exhibited enhanced antioxidative activities compared with their physically mixed counterparts. The digested MRPs displayed excellent resistance to pathogenic bacteria and promoted the growth of L. casei. Moreover, MRP-encapsulated L. casei showed a higher survival rate than free L. casei under tested adverse conditions including heat treatment, storage, and mechanical forces. Under simulated digestion conditions, the viability of L. casei decreased from 8.8 log cfu/mL to 1.6 log cfu/mL, while that of MRP-encapsulated L. casei was maintained at 7.4 log cfu/mL. Thus, MRP-based SPI-oligosaccharide conjugates exhibited great potential for microencapsulation of probiotics.

Structure-guided protein engineering of ammonia lyase for efficient synthesis of sterically bulky unnatural amino acids

Enzymatic asymmetric amination addition is seen as a promising approach for synthesizing amine derivatives, especially unnatural amino acids, which are valuable precursors to fine chemicals and drugs. Despite the broad substrate spectrum of methylaspartate lyase (MAL), some bulky substrates, such as caffeic acid, cannot be effectively accepted. Herein, we report a group of variants structurally derived from Escherichia coli O157:H7 MAL (EcMAL). A combined mutagenesis strategy was used to simultaneously redesign the key residues of the entrance tunnel and binding pocket to explore the possibility of accepting bulky substrates with potential application to chiral drug synthesis. Libraries of residues capable of lining the active center of EcMAL were then constructed and screened by an effective activity solid-phase color screening method using tyrosinase as a cascade catalyst system. Activity assays and molecular dynamics studies of the resultant variants showed that the substrate specificity of EcMAL was modified by adjusting the polarity of the binding pocket and the degree of flexibility of the entrance tunnel. Compared to M3, the optimal variant M8 was obtained with a 15-fold increase in catalytic activity. This structure-based protein engineering of EcMAL can be used to open new application directions or to develop practical multi-enzymatic processes for the production of various useful compounds.

Investigation of hierarchically porous zeolitic imidazolate frameworks for highly efficient dye removal

Treatment of textile water containing organic molecules as contaminants still remains a challenge and has become a central issue for environment remediation. Here, a nucleotide incorporated zeolitic imidazolate frameworks (NZIF) featuring hierarchically porous structure served as a potential adsorbent for removal of organic dye molecules. Adsorption isotherms of organic dyes were accurately described by Langmuir adsorption model with correlation coefficients of 0.98 and kinetic data followed the pseudo-second-order model. The maximum adsorption capacity of NZIF for Congo red (CR) and methylene blue (MB) reached 769 and 10 mg/g, respectively, which were 6 and 5 times higher than that of ZIF-8. The adsorption behavior of sunset yellow and crystal violet was examined for mechanism investigation. Analysis of pore size, molecular size, zeta potential and FTIR measurement together revealed that mesopores in NZIF provided more interaction sites and led to enhanced adsorption capacity. Hydrogen bonding and π-π stacking which resulted from the interaction between introduced nucleotide monophosphate and dyes dominated the driving forces for adsorption, where electrostatic interaction was also involved. Moreover, the introduced nucleoside monophosphate enabled NZIF to function under acidic condition whereas ZIF-8 collapsed. This study opens a new avenue for design of porous materials for environment remediation.

Chemoenzymatic access to enantiopure N-containing furfuryl alcohol from chitin-derived N-acetyl-D-glucosamine

BACKGROUND

Chiral furfuryl alcohols are important precursors for the synthesis of valuable functionalized pyranones such as the rare sugar L-rednose. However, the synthesis of enantiopure chiral biobased furfuryl alcohols remains scarce. In this work, we present a chemoenzymatic route toward enantiopure nitrogen-containing (R)- and (S)-3-acetamido-5-(1-hydroxylethyl)furan (3A5HEF) from chitin-derived N-acetyl-D-glucosamine (NAG).

FINDINGS

3-Acetamido-5-acetylfuran (3A5AF) was obtained from NAG via ionic liquid/boric acid-catalyzed dehydration, in an isolated yield of approximately 31%. Carbonyl reductases from Streptomyces coelicolor (ScCR) and Bacillus sp. ECU0013 (YueD) were found to be good catalysts for asymmetric reduction of 3A5AF. Enantiocomplementary synthesis of (R)- and (S)-3A5HEF was implemented with the yields of up to  >  99% and the enantiomeric excess (ee) values of  >  99%. Besides, biocatalytic synthesis of (R)-3A5HEF was demonstrated on a preparative scale, with an isolated yield of 65%.

CONCLUSIONS

A two-step process toward the chiral furfuryl alcohol was successfully developed by integrating chemical catalysis with enzyme catalysis, with excellent enantioselectivities. This work demonstrates the power of the combination of chemo- and biocatalysis for selective valorization of biobased furans.

Engineering Promiscuous Alcohol Dehydrogenase Activity of a Reductive Aminase AspRedAm for Selective Reduction of Biobased Furans

Catalytic promiscuity is a promising starting point for improving the existing enzymes and even creating novel enzymes. In this work, site-directed mutagenesis was performed to improve promiscuous alcohol dehydrogenase activity of reductive aminase from Aspergillus oryzae (AspRedAm). AspRedAm showed the cofactor preference toward NADPH in reductive aminations, while it favored NADH in the reduction reactions. Some key amino acid residues such as N93, I118, M119, and D169 were identified for mutagenesis by molecular docking. Variant N93A showed the optimal pH and temperature of 8 and 30°C, respectively, in the reduction of 5-hydroxymethylfurfural (HMF). The thermostability was enhanced upon mutation of N93 to alanine. The catalytic efficiency of variant N93A (k_cat/K_m, 23.6 mM⁻¹ s⁻¹) was approximately 2-fold higher compared to that of the wild-type (WT) enzyme (13.1 mM⁻¹ s⁻¹). The improved catalytic efficiency of this variant may be attributed to the reduced steric hindrance that stems from the smaller side chain of alanine in the substrate-binding pocket. Both the WT enzyme and variant N93A had broad substrate specificity. Escherichia coli (E. coli) cells harboring plain vector enabled selective reduction of biobased furans to target alcohols, with the conversions of 35–95% and the selectivities of >93%. The introduction of variant N93A to E. coli resulted in improved substrate conversions (>98%) and selectivities (>99%).

A Versatile Competitive Coordination Strategy for Tailoring Bioactive Zeolitic Imidazolate Framework Composites

Zeolitic imidazolate frameworks (ZIFs) serving as platforms for bioactive guest encapsulation have attracted growing attention, yet the tailoring of its architectures and bioactivity remains a major challenge. Herein, a versatile competitive coordination strategy is proposed by using amorphous zinc nucleotide gel as template for step-by-step growth of ZIFs, which enables the tailoring of bioactive ZIF composites under facile conditions. Mechanism investigation reveals that introduced nucleotide determines the hierarchical pore structure and hydrophilicity, leading to customized activity retention and stability of the resultant bioactive ZIF composites. Furthermore, nucleoside monophosphate enhances the acidic tolerance of ZIFs. To the authors' knowledge, this is the first example showing the dynamic evolution of amorphous gels to crystalline ZIFs for in situ encapsulation of enzymes with tailored catalytic performance. This study provides insights for rational design of ZIF-based biocomposites and broadens the application of bioactive metal-organic frameworks.

Fabrication of Nano/Micro-Structured Electrospun Detection Card for the Detection of Pesticide Residues

A novel nano/micro-structured pesticide detection card was developed by combining electrospinning and hydrophilic modification, and its feasibility for detecting different pesticides was investigated. Here, the plain and hydrophilic-modified poly(ε-caprolactone) (PCL) fiber mats were used for the absorption of indolyl acetate and acetylcholinesterase (AChE), respectively. By pre-treating the fiber mat with ethanol, its surface wettability was improved, thus, promoting the hydrolysis of the PCL fiber mat. Furthermore, the absorption efficiency of AChE was improved by almost two times due to the increased hydrophilicity of the modified fiber mat. Noteworthily, this self-made detection card showed a 5-fold, 2-fold, and 1.5-fold reduction of the minimum detectable concentration for carbofuran, malathion, and trichlorfon, respectively, compared to the national standard values. Additionally, it also exhibited good stability when stored at 4 °C and room temperature. The food detection test showed that this nano/micro-based detection card had better detectability than the commercial detection card. Therefore, this study offers new insights into the design of pesticide detection cards, which also broadens the application of electrospinning technique.

Bioinspired Cooperative Photobiocatalytic Regeneration of Oxidized Nicotinamide Cofactors for Catalytic Oxidations

Invited for this month's cover is the group of Ning Li at South China University of Technology. The image shows an efficient photobiocatalytic system to regenerate oxidized nicotinamide cofactors for dehydrogenase-mediated oxidations. The Communication itself is available at 10.1002/cssc.202100184.

Bioinspired Cooperative Photobiocatalytic Regeneration of Oxidized Nicotinamide Cofactors for Catalytic Oxidations

Inspired by water-forming NAD(P)H oxidases, a cooperative photobiocatalytic system has been designed to aerobically regenerate the oxidized nicotinamide cofactors. Photocatalysts enable NAD(P)H oxidation with O₂ under visible-light irradiation, producing H₂ O₂ as a byproduct, which is subsequently used as an oxidant by the horseradish peroxidase mediator system (PMS) to oxidize NAD(P)H. The photobiocatalytic system shows a turnover frequency of 8800 min^-1 in the oxidation of NAD(P)H. Photobiocatalytic NAD(P)H oxidation proceeds smoothly at pH 6-9. In addition to natural NAD(P)H, synthetic biomimetics are also good substrates for this regeneration system. Total turnover numbers of up to 180000 are obtained for the cofactor when the photobiocatalytic regeneration system is coupled with dehydrogenase-catalyzed oxidations. It may be a promising protocol to recycle the oxidized cofactors for catalytic oxidations.

Fabrication of nanostructured multi-unit vehicle for intestinal-specific delivery and controlled release of peptide

An oral multi-unit delivery system was developed by incorporating the nanoparticle (NP) into the nanofiber mat and its efficiency for intestinal-specific delivery and controlled release of a peptide (insulin) was investigated. Initially, the influence of deacetylation degree (DD) of chitosan and ionic gelation methods on the properties of NPs was studied. High DD (95%) chitosan was attributed to higher encapsulation efficiency and stability when crosslinked with polyanion tripolyphosphate. Subsequently, the multi-unit system was fabricated using a pH-sensitive polymer (sodium alginate) as the coating layer to further encapsulate the NP. Fiber mat with an average diameter of 481 ± 47 nm could significantly decrease the burst release of insulin in acidic condition and release most amount of insulin (>60%) in the simulated intestinal medium. Furthermore, the encapsulated peptide remained in good integrity. This multi-unit carrier provides the better-designed vehicle for intestinal-specific delivery and controlled release of the peptide.

Oral fate and stabilization technologies of lactoferrin: a systematic review

Lactoferrin (Lf), a bioactive protein initially found in many biological secretions including milk, is regarded as the nutritional supplement or therapeutic ligand due to its multiple functions. Research on its mode of action reveals that intact Lf or its active peptide (i.e., lactoferricin) shows an important multifunctional performance. Oral delivery is considered as the most convenient administration route for this bioactive protein. Unfortunately, Lf is sensitive to the gastrointestinal (GI) physicochemical stresses and lactoferricin is undetectable in GI digesta. This review introduces the functionality of Lf at the molecular level and its degradation behavior in GI tract is discussed in detail. Subsequently, the absorption and transport of Lf from intestine into the blood circulation, which is pivotal to its health promoting effects in various tissues, and some assisting labeling methods are discussed. Stabilization technologies aiming at preserving the structural integrity and functional properties of orally administrated Lf are summarized and compared. Altogether, this work comprehensively reviews the structure-function relationship of Lf, its oral fate and the development of stabilization technologies for the enhancement of the oral bioavailability of Lf. The existing limitations and scope for future research are also discussed.

Biotechnology and bioengineering of pullulanase: state of the art and perspectives

Pullulanase (EC 3.2.1.41) is a starch-debranching enzyme in the α-amylase family and specifically cleaves α-1,6-glycosidic linkages in starch-type polysaccharides, such as pullulan, β-limited dextrin, glycogen, and amylopectin. It plays a key role in debranching and hydrolyzing starch completely, thus bring improved product quality, increased productivity, and reduced production cost in producing resistant starch, sugar syrup, and beer. Plenty of researches have been made with respects to the discovery of either thermophilic or mesophilic pullulanases, however, few examples meet the demand of industrial application. This review presents the progress made in the recent years from the first aspect of characteristics of pullulanases. The heterologous expression of pullulanases in different microbial hosts and the methods used to improve the expression effectiveness and the regulation of enzyme production are also described. Then, the function evolution of pullulanases from a protein engineering view is discussed. In addition, the immobilization strategy using novel materials is introduced to improve the recyclability of pullulanases. At the same time, we indicate the trends in the future research to facilitate the industrial application of pullulanases.

Combinatorial synthetic pathway fine-tuning and cofactor regeneration for metabolic engineering of Escherichia coli significantly improve production of D-glucaric acid

D-glucaric acid (GA) has been identified as among promising biotechnological alternatives to oil-based chemicals. GA and its derivatives are widely used in food additives, dietary supplements, drugs, detergents, corrosion inhibitors and biodegradable materials. The increasing availability of a GA market is improving the cost-effectiveness and efficiency of various biosynthetic pathways. In this study, an engineered Escherichia coli strain GA10 was constructed by systematic metabolic engineering. This involved redirecting metabolic flux into the GA biosynthetic pathways, blocking the conversion pathways of d-glucuronic acid (GlcA) and GA into by-products, introducing an in situ NAD⁺ regeneration system and fine-tuning the activity of the key enzyme, myo-inositol oxygenase (Miox). Subsequently, the culture medium was optimized to achieve the best performance of the GA10 strain. GA was produced at 5.35 g/L (extracellular and intracellular), with a maximized yield of ∼0.46 mol/mol on d-glucose and glycerol, by batch fermentation. This work demonstrates efficient biosynthetic pathways of GA in E. coli by metabolic engineering and should accelerate the application of GA biosynthetic pathways in industrial processes.

Bioprospecting of a novel endophytic Bacillus velezensis FZ06 from leaves of Camellia assamica: Production of three groups of lipopeptides and the inhibition against food spoilage microorganisms

Food contamination caused by microorganisms has become a threat to consumers' health. Exploring antagonistic endophytes from plants of food raw-material and applying bioactive metabolites to inhibit the contamination has been an alternative and safer solution. In this study, we isolated and screened potential antagonistic endophytes from fresh Camellia assamica leaves, which were widely used in tea beverage production. We focused on a strain that showed visible inhibitory activity to Gram-positive bacteria, Gram-negative bacteria, and fungi. It was identified as a member of Bacillus velezensis and named FZ06. The results of genome analysis showed the strain FZ06 had 167 single-copy specific genes, much higher than those of most related strains. Also, 11 potential gene clusters of antimicrobial metabolites were found. Three groups of lipopeptides (surfactin, iturin, and fengycin) were identified by UPLC-MS/MS in purified antimicrobial methanol fraction of strain FZ06. The results of minimum inhibitory concentration (MIC) test proved the lipopeptide extract showed significant inhibitory effect on food spoilage bacteria (MIC 512-2048 μg/mL) and toxigenic fungi (MIC 128-256 μg/mL). In conclusion, this study suggests that the endophytic B. velezensis FZ06 and its lipopeptide extract hold great potential applications in the inhibition of food spoilage bacteria and toxic fungi in food industry.

Recruiting a Phosphite Dehydrogenase/Formamidase-Driven Antimicrobial Contamination System in Bacillus subtilis for Nonsterilized Fermentation of Acetoin

Microbial contamination, especially in large-scale processes, is partly a life-or-death issue for industrial fermentation. Therefore, the aim of this research was to create an antimicrobial contamination system in Bacillus subtilis 168 (an ideal acetoin producer for its safety and acetoin synthesis potential). First, introduction of the formamidase (FmdA) from Helicobacter pylori and the phosphite dehydrogenase (PtxD) from Pseudomonas stutzeri enabled the engineered Bacillus subtilis to simultaneously assimilate formamide and phosphite as nitrogen (N) and phosphorus (P) sources. Thus, the engineered B. subtilis became the dominant population in a potentially contaminated system, while contaminated microbes were starved of key nutrients. Second, stepwise metabolic engineering via chromosome-based overexpression of the relevant glycolysis and acetoin biosynthesis genes led to a 1.12-fold increment in acetoin titer compared with the starting host. Finally, with our best acetoin producer, 25.56 g/L acetoin was synthesized in the fed-batch fermentation, with a productivity of 0.33 g/L/h and a yield of 0.37 g/g under a nonsterilized and antibiotic-free system. More importantly, our work fulfills many key criteria of sustainable chemistry since sterilization is abolished, contributing to the simplified fermentation operation with lower energy consumption and cost.

Facile and Green Production of Human Milk Fat Substitute through Rhodococcus opacus Fermentation

Human milk fat substitute (HMFS) is a class of structured lipids widely used in infant formulas. Herein, HMFS was prepared by Rhodococcus opacus fermentation. The substrate oils suitable for HMFS production were coconut oil (66.1-57.5%), soybean oil (17.5-26.5%), high oleic acid sunflower oil (5.4-4.5%), Antarctic krill oil (9-9.5%), and fungal oil (2%). Six HMFSs were prepared, among which HMFS V and VI were similar to human milk fat from Chinese in terms of fatty acid composition and triacylglycerol species. The sn-2 position of HMFS was occupied by palmitic acid (49.31 and 43.48% in HMFS V and VI, respectively). The major triacylglycerols were OPL, OPO, and LPL, accounting for 15.90, 9.49, and 6.84 and 17.52, 8.44, and 8.55% in HMFS V and VI, respectively. This study is the first to prepare structured lipids intended for infant formula through fermentation, providing a novel strategy for the edible oil industry.

Development of a novel nano-based detection card by electrospinning for rapid and sensitive analysis of pesticide residues

BACKGROUND

Increasing food safety awareness of consumers promotes the development of rapid and sensitive detection techniques for pesticide residues. In this study, a new type of rapid detection card for organophosphorus and carbamate pesticide residues was developed by electrospinning. The card involved enzyme fiber mat (EFM) and substrate fiber mat (SFM) which were prepared by mixing poly(vinyl alcohol) with acetylcholinesterase (AChE) and indolyl acetate (IA), respectively.

RESULTS

The mean diameter of fibers was 240 ± 53 nm for EFM and 387 ± 84 nm for SFM. Results of Fourier transform infrared and X-ray photoelectron spectroscopies confirmed that AChE and IA were successfully encapsulated into the fibers. The minimum concentrations of AChE and IA for effective detection were 1 and 3 mg mL^-1 , respectively, and the optimal detection time was 15 min. The limits of detection for this card were 0.5 mg L^-1 for omethoate, 1.5 mg L^-1 for malathion, 0.1 mg L^-1 for carbaryl and 0.02 mg L^-1 for carbofuran. The detection card exhibited good storage stability and its activity could be maintained when stored at room temperature for at least 4 months. Additionally, the EFM can be reused three times.

CONCLUSIONS

The detection card obtained here was superior to a commercial card in detecting pesticide residues in real food samples. Hence, this electrospun detection card has potential for simple, rapid and sensitive analysis of pesticide residues. © 2020 Society of Chemical Industry.

Carbon source modify lipids composition of Rhodococcus opacus intended for infant formula

Human milk fat substitutes (HMFSs) are the structured lipids intended for infant formula. It provides energy and essential fatty acid for infant. HMFSs are mainly prepared by enzymatic method. In this study, we aim to explore the potential for producing HMFSs by fermentation using R. opacus. The results indicated that different compounds with chain length from 12 to 18, used as carbon source, could be incorporated into triacylglycerols directly. Polyunsaturated fatty acids in term of ARA, EPA, DHA could enter the kennedy pathway directly and involved in the biosynthesis of triacylglycerols. GC, UPLC-MS and ¹³C-NMR analysis demonstrated that typical structured lipids β-OPL (40.09%) was synthesized in R. opacus. Transcriptome analysis revealed that β-oxidation, fatty acid elongation and kennedy pathways existed in R. opacus. It was concluded that fatty acid supplied as carbon source could enter the kennedy pathways directly or via the de novo fatty acid biosynthesis pathway depending on the chain length, thus, affect the triacylglycerol species formed in the Rhodococcus opacus.

A novel Pickering emulsion system as the carrier of tocopheryl acetate for its application in cosmetics

Pickering emulsion (PE) stabilized by bio-compatible polymer nanoparticles (NPs) was first developed for the encapsulation of lipophilic tocopheryl acetate (TA) for its application in cosmetics. The poly(lactide-co-glycolide) (PLGA)/poly(styrene-co-4-styrene-sulfonate) (PSS) NPs were prepared by solvent displacement, and then they were used as emulsifier particles to fabricate TA-encapsulated PE. It was found that the TA encapsulation efficiency was >98%. Scanning electron microscope analysis showed that the obtained PE exhibited 'shell' structure. The PE droplets had spherical shape with diameter around 2 μm and good dispersibility as evidenced by laser scanning confocal microscope. In addition, the PE was stable at the pH range of 4.29-7.07 which was compatible to skin pH. Meanwhile, the PE also showed good storage stability since there was no obvious change in its diameter, PDI and TA retention after storage at 4 °C for 30 days. The DPPH method confirmed that TA retained its antioxidation in the PE preparation process. Moreover, an improved UV irradiation stability was observed for the TA after being encapsulated in the PE. The results of cytotoxicity test suggested that the PE was compatible to the Hacat cell line (human immortalized keratinocytes). And there is negligible influence in the cellular uptake of TA after its encapsulation in the PE. However, the cellular antioxidant activity (CAA) of encapsulated TA presented a significant increase from 1.32 to 1.56 μM quercetin equivalent/mg·mL^-1. Hence, the prepared PE was promising as the carrier of TA for its cosmetic application.

Immobilization of Cofactor Self-Sufficient Recombinant Escherichia coli for Enantioselective Biosynthesis of (R)-1-Phenyl-1,2-Ethanediol

(R)-1-phenyl-1,2-ethanediol is an important synthon for the preparation of β-adrenergic blocking agents. This study identified a (2R,3R)-butanediol dehydrogenase (KgBDH) from Kurthia gibsonii SC0312, which showed high enantioselectivity for production of (R)-1-phenyl-1,2-ethanediol by reduction of 2-hydroxyacetophenone. KgBDH was expressed in a recombinant engineered strain, purified, and characterized. It showed good catalytic activity at pH 6–8 and better stability in alkaline (pH 7.5–8) than an acidic environment (pH 6.0–7.0), providing approximately 73 and 88% of residual activity after 96 h at pH 7.5 and 8.0, respectively. The maximum catalytic activity was obtained at 45°C; nevertheless, poor thermal stability was observed at >30°C. Additionally, the examined metal ions did not activate the catalytic activity of KgBDH. A recombinant Escherichia coli strain coexpressing KgBDH and glucose dehydrogenase (GHD) was constructed and immobilized via entrapment with a mixture of activated carbon and calcium alginate via entrapment. The immobilized cells had 1.8-fold higher catalytic activity than that of cells immobilized by calcium alginate alone. The maximum catalytic activity of the immobilized cells was achieved at pH 7.5, and favorable pH stability was observed at pH 6.0–9.0. Moreover, the immobilized cells showed favorable thermal stability at 25–30°C and better operational stability than free cells, retaining approximately 55% of the initial catalytic activity after four cycles. Finally, 81% yields (195 mM product) and >99% enantiomeric excess (ee) of (R)-1-phenyl-1,2-ethanediol were produced within 12 h through a fed-batch strategy with the immobilized cells (25 mg/ml wet cells) at 35°C and 180 rpm, with a productivity of approximately 54 g/L per day.