Thymosin beta 10 loaded ZIF-8/sericin hydrogel promoting angiogenesis and osteogenesis for bone regeneration.

Angiogenesis is pivotal for osteogenesis during bone regeneration. A hydrogel that promotes both angiogenesis and osteogenesis is essential in bone tissue engineering. However, creating scaffolds with the ideal balance of biodegradability, osteogenic, and angiogenic properties poses a challenge. Thymosin beta 10 (TMSB10), known for its dual role in angiogenesis and osteogenesis differentiation, faces limitations due to protein activity preservation. To tackle this issue, ZIF-8 was engineered as a carrier for TMSB10 (TMSB10@ZIF-8), and subsequently integrated into the self-assembled sericin hydrogel. The efficacy of the composite hydrogel in bone repair was assessed using a rat cranial defect model. Characterization of the nanocomposites confirmed the successful synthesis of TMSB10@ZIF-8, with a TMSB10 encapsulation efficiency of 88.21 %. The sustained release of TMSB10 from TMSB10@ZIF-8 has significantly enhanced tube formation in human umbilical vein endothelial cells (HUVECs) in vitro and promoted angiogenesis in the chicken chorioallantoic membrane (CAM) model in vivo. It has markedly improved the osteogenic differentiation ability of MC 3 T3-E1 cells in vitro. 8 weeks post-implantation, the TMSB10@ZIF-8/ Sericin hydrogel group exhibited significant bone healing (86.77 ± 8.91 %), outperforming controls. Thus, the TMSB10@ZIF-8/Sericin hydrogel, leveraging ZIF-8 for TMSB10 delivery, emerges as a promising bone regeneration scaffold with substantial clinical application potential.

Kaempferol 3-O-Rutinoside, a Flavone Derived from Tetrastigma hemsleyanum Diels et Gilg, Reduces Body Temperature through Accelerating the Elimination of IL-6 and TNF-α in a Mouse Fever Model.

Fever is a serious condition that can lead to various consequences ranging from prolonged illness to death. Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) has been used for centuries to treat fever, but the specific chemicals responsible for its antipyretic effects are not well understood. This study aimed to isolate and identify the chemicals with antipyretic bioactivity in T. hemsleyanum extracts and to provide an explanation for the use of T. hemsleyanum as a Chinese herbal medicine for fever treatment. Our results demonstrate that kaempferol 3-rutinoside (K3OR) could be successfully isolated and purified from the roots of T. hemsleyanum. Furthermore, K3OR exhibited a significant reduction in rectal temperature in a mouse model of fever. Notably, a 4 µM concentration of K3OR showed more effective antipyretic effects than ibuprofen and acetaminophen. To explore the underlying mechanism, we conducted an RNA sequencing analysis, which revealed that PXN may act as a key regulator in the fever process induced by lipopolysaccharide (LPS). In the mouse model of fever, K3OR significantly promoted the secretion of IL-6 and TNF-α during the early stage in the LPS-treated group. However, during the middle to late stages, K3OR facilitated the elimination of IL-6 and TNF-α in the LPS-treated group. Overall, our study successfully identified the chemicals responsible for the antipyretic bioactivity in T. hemsleyanum extracts, and it answered the question as to why T. hemsleyanum is used as a traditional Chinese herbal medicine for treating fever. These findings contribute to a better understanding of the therapeutic potential of T. hemsleyanum in managing fever, and they provide a basis for further research and development in this field.

Anti-Inflammatory Effect of Columbianadin against D-Galactose-Induced Liver Injury In Vivo via the JAK2/STAT3 and JAK2/p38/NF-κB Pathways.

Angelicae pubescentis radix (APR) has been traditionally used for thousands of years in China to treat rheumatoid arthritis (RA), an autoimmune disorder. As the main active coumarin of APR, columbianadin (CBN) exhibits a significant anti-inflammatory effect in vitro. However, the anti-inflammatory activity and underlying mechanism of CBN in vivo remain unclear. This work aimed to elucidate the anti-inflammatory activity of CBN in vivo and its related signaling pathways in a D-Gal-induced liver injury mouse model. Analysis of biochemical indices (ALT and AST) and pro-inflammatory cytokines (IL-1ß and IL-6) in serum indicated that CBN significantly ameliorated D-Gal-induced liver injury. CBN treatment also significantly increased the activities of antioxidant enzymes (SOD, CAT, GPx), and decreased the levels of pro-inflammatory cytokines (TNF-α, IL-1ß and IL-6) in liver tissue. Liver histology revealed that CBN treatment reduced hepatic inflammation. Western blot analysis indicated that CBN down-regulates the expression of phosphorylated JAK2, STAT3, MAPK, and NF-κB in the related signaling pathways. These findings support the traditional use of APR as a remedy for the immune system, and indicate that the JAK2/STAT3 and JAK2/p38/NF-κB signaling pathways may be important mechanisms for the anti-inflammatory activity of CBN in vivo.

Enhanced catalytic activity and stability of lactate dehydrogenase for cascade catalysis of D-PLA by rational design.

Serving as a vital medical intermediate and an environmentally-friendly preservative, D-PLA exhibits substantial potential across various industries. In this report, the urgent need for efficient production motivated us to achieve the rational design of lactate dehydrogenase and enhance catalytic efficiency. Surprisingly, the enzymatic properties revealed that a mutant enzyme, LrLDHT247I/D249A/F306W/A214Y (LrLDH-M1), had a viable catalytic advantage. It demonstrated a 3.3-fold increase in specific enzyme activity and approximately a 2.08-fold improvement of Kcat. Correspondingly, molecular docking analysis provided a supporting explanation for the lower Km and higher Kcat/Km of the mutant enzyme. Thermostability analysis exhibited increased half-lives and the deactivation rate constants decreased at different temperatures (1.47-2.26-fold). In addition, the mutant showed excellent resistance abilities in harsh environments, particularly under acidic conditions. Then, a two-bacterium (E. coli/pET28a-lrldh-M1 and E. coli/pET28a-ladd) coupled catalytic system was developed and realized a significant conversion rate (77.7%) of D-phenyllactic acid, using 10 g/L L-phenylalanine as the substrate in a two-step cascade reaction.

A review on chitosan/metal oxide nanocomposites for applications in environmental remediation.

A cleaner and safer environment is one of the most important requirements in the future. It has become increasingly urgent and important to fabricate novel environmentally-friendly materials to remove various hazardous pollutants. Compared with traditional materials, chitosan is a more environmentally friendly material due to its abundance, biocompatibility, biodegradability, film-forming ability and hydrophilicity. As an abundant of -NH2 and -OH groups on chitosan molecular chain could chelate with all kinds of metal ions efficiently, chitosan-based materials hold great potential as a versatile supporting matrix for metal oxide nanomaterials (MONMs) (TiO2, ZnO, SnO2, Fe3O4, etc.). Recently, many chitosan/metal oxide nanomaterials (CS/MONMs) have been reported as adsorbents, photocatalysts, heterogeneous Fenton-like agents, and sensors for potential and practical applications in environmental remediation and monitoring. This review analyzed and summarized the recent advances in CS/MONMs composites, which will provide plentiful and meaningful information on the preparation and application of CS/MONMs composites for wastewater treatment and help researchers to better understand the potential of CS/MONMs composites for environmental remediation and monitoring. In addition, the challenges of CS/MONM have been proposed.

Degradation Kinetic Studies of BSA@ZIF-8 Nanoparticles with Various Zinc Precursors, Metal-to-Ligand Ratios, and pH Conditions.

Nanosized zeolitic imidazolate framework particles (ZIF-8 nanoparticles [NPs]) have strong potential as effective carriers for both in vivo and in vitro protein drug delivery. Synthesis of ZIF-8 and stability of protein encapsulation within ZIF-8 are affected by several factors, notably the metal ion source and molar ratio. To systematically investigate these factors, we investigated such effects using BSA as a model test protein to synthesize BSA@ZIF-8 NPs at various metal-to-ligand (M:L) ratios. SEM, FTIR, XRD, and DLS were applied to characterize the morphology and structure of BSA@ZIF-8 NPs and their effects on protein loading capacity. Degradation kinetics and protein release behavior of BSA@ZIF-8 NPs were evaluated at pH 5.0 (to simulate the tumor environment) and pH 7.4 (to mimic the blood environment). Our objective was to define optimal combinations of the high protein loading rate and rapid release under varying pH conditions, and we found that (i) the yield of BSA@ZIF-8 NPs decreased as the M:L ratio increased, but the protein content increased. This highlights the need to strike a balance between cost-effectiveness and practicality when selecting ZIF-8 NPs with different molar ratios for protein-based drug formulation. (ii) BSA@ZIF-8 NPs exhibited cruciate flower-like shapes when synthesized using Zn(NO3)2 as the zinc precursor at M:L ratios of 1:16 or 1:20. In all other cases, the NPs displayed a regular rhombic dodecahedral structure. Notably, the release behavior of the NPs did not differ significantly between these morphologies. (iii) When Zn(OAc)2 was used as the zinc precursor, the synthesized ZIF-8 NPs exhibited a smaller size compared to the Zn(NO3)2-derived ZIF-8 NPs. (iv) The release rate and amount of BSA protein were higher at pH 5.0 compared to pH 7.4. (v) Among the different formulations, BSA@ZIF-8 with an M:L ratio of 1:16 at pH 5.0 was observed to have a shorter time to reach a plateau (0.5 h) and higher protein release, making it suitable for locally rapid administration in a tumor environment. BSA@ZIF-8 prepared from Zn(OAc)2 at an M:L ratio of 1:140 showed the slower release of BSA protein over a 24-h period, indicating its suitability for sustained release delivery. In conclusion, our findings provide a useful basis for the practical application of ZIF-8 NPs in protein-based drug delivery systems.

Development of a Strategy for L-Lactic Acid Production by Rhizopus oryzae Using Zizania latifolia Waste and Cane Molasses as Carbon Sources.

As a biodegradable and renewable material, polylactic acid is considered a major environmentally friendly alternative to petrochemical plastics. Microbial fermentation is the traditional method for lactic acid production, but it is still too expensive to compete with the petrochemical industry. Agro-industrial wastes are generated from the food and agricultural industries and agricultural practices. The utilization of agro-industrial wastes is an important way to reduce costs, save energy and achieve sustainable development. The present study aimed to develop a method for the valorization of Zizania latifolia waste and cane molasses as carbon sources for L-lactic acid fermentation using Rhizopus oryzae LA-UN-1. The results showed that xylose derived from the acid hydrolysis of Z. latifolia waste was beneficial for cell growth, while glucose from the acid hydrolysis of Z. latifolia waste and mixed sugars (glucose and fructose) from the acid hydrolysis of cane molasses were suitable for the accumulation of lactic acid. Thus, a three-stage carbon source utilization strategy was developed, which markedly improved lactic acid production and productivity, respectively reaching 129.47 g/L and 1.51 g/L·h after 86 h of fermentation. This work demonstrates that inexpensive Z. latifolia waste and cane molasses can be suitable carbon sources for lactic acid production, offering an efficient utilization strategy for agro-industrial wastes.

Lupeol-loaded chitosan-Ag+ nanoparticle/sericin hydrogel accelerates wound healing and effectively inhibits bacterial infection.

Lupeol, a pentacyclic triterpene, has demonstrated significant wound healing properties; however, its low water solubility has limited its clinical applicability. To overcome this limitation, we utilized Ag+-modified chitosan (CS-Ag) nanoparticles to deliver lupeol, resulting in the formation of CS-Ag-L-NPs. These nanoparticles were then encapsulated within a temperature-sensitive, self-assembled sericin hydrogel. Various analytical methods, including SEM, FTIR, XRD, HPLC, TGA assay, hemolysis and antibacterial activity tests, were employed to characterize the nanoparticles. Additionally, an infectious wound model was used to evaluate the therapeutic and antibacterial efficacy of the CS-Ag-L-NPs modified sericin hydrogel. Our results showed that the encapsulation efficiency of lupeol in CS-Ag-L-NPs reached 62.1 %, with good antibacterial activity against both gram-positive and gram-negative bacteria and a low hemolysis ratio (<5 %). The CS-Ag-L-NPs sericin gel exhibited multiple beneficial effects, including inhibiting bacterial proliferation in wound beds, promoting wound healing via accelerated re-epithelialization, reducing inflammation, and enhancing collagen fiber deposition. We conclude that the CS-Ag-L-NPs loaded sericin hydrogel has tremendous potential for development as a multifunctional therapeutic platform capable of accelerating wound healing and effectively suppressing bacterial infections in clinical settings.

Isolation and screening of a chitin deacetylase producing Bacillus cereus and its potential for chitosan preparation.

Chitosan is a biopolymer material extracted from marine biomass waste such as shrimp and crab shells, which has good biocompatibility and degradability with great potential for application in the field of wastewater treatment and soil remediation. The higher the degree of deacetylation (DD), the better the adsorption performance of chitosan. Chitin deacetylase (CDA) can specifically catalyze the deacetylate of chitin in a green reaction that is environmentally friendly. However, the scarcity of high yielding chitin deacetylase strains has been regarded as the technical bottleneck of chitosan green production. Here, we screened a natural chitin degrading bacterium from coastal mud and identified it as Bacillus cereus ZWT-08 by re-screening the chitin deacetylase activity and degree of deacetylation values. By optimizing the medium conditions and enzyme production process, ZWT-08 was cultured in fermentation medium with 1% (m/V) glucose and yeast extract at pH 6.0, 37°C, and a stirring speed of 180 r/min. After fermenting in 5 L fermenter for 48 h, the deacetylation activity of the supernatant reached 613.25 U/mL. Electron microscopic examination of the chitin substrate in the fermentation medium revealed a marshmallow-like fluffy texture on its structural surface. Meanwhile, 89.29% of the acetyl groups in this chitin substrate were removed by enzymatic digestion of chitin deacetylase produced by ZWT-08, resulting in the preparation of chitosan a degree of deacetylation higher than 90%. As an effective strain for chitosan production, Bacillus cereus ZWT-08 plays a positive role in the bioconversion of chitin and the upgrading of the chitosan industry.

Comparing the Volatile and Soluble Profiles of Fermented and Integrated Chinese Bayberry Wine with HS-SPME GC-MS and UHPLC Q-TOF.

To evaluate the flavor characteristics of Chinese bayberry alcoholic beverages, fermented bayberry wine (FBW) and integrated bayberry wine (IBW) were investigated for their volatile and soluble profiles using HS-SPME GC-MS and UHPLC Q-TOF and were analyzed with multidimensional statistical analysis, including PCA and OPLS-DA. The volatile compounds 1-pentanol, ß-caryophyllene and isopentanol were only detected in IBW. ß-caryophyllene, the key flavor component of bayberry, was found to be the most abundant volatile compound in IBW (25.89%) and was 3.73 times more abundant in IBW than in FBW. The levels of ethyl octanoate, ethyl nonanoate, and ethyl decanoate were also several times higher in IBW than in FBW. These compounds contributed to the strong bayberry aroma and better fruity flavor of IBW. On the other hand, high levels of ethyl acetate and octanoic acid in FBW, representing pineapple/overripe or sweat odor, were key contributors to the fermented flavor of FBW. Soluble sugars, such as sucrose, D-glucose, and D-tagatose, as well as amino acids, such as L-glutamate and L-aspartate, had much higher levels in IBW. The anthocyanin pigment cyanidin 3-glucoside, which generates red color, was also higher in IBW. On the other hand, most of the differentially expressed alcohols, acids, amino acids, purines/pyrimidines and esters were present in higher concentrations in FBW compared to IBW. This demonstrated that IBW has a much sweeter and more savory taste as well as a better color generated by more anthocyanins, while FBW presents a more acidic and drier taste as well as a complex formation of alcohols and esters. The study also prompts the need for further research on the flavor profiles of IBW and its potential application and market value.

A two-enzyme system in an amorphous metal-organic framework for the synthesis of D-phenyllactic acid.

In this study, we synthesized an amorphous metal-organic framework by adjusting the concentration of precursors, and established a two-enzyme system consisting of lactate dehydrogenase (LDH) and glucose dehydrogenase (GDH), which successfully achieved coenzyme recycling, and applied it to the synthesis of D-phenyllactic acid (D-PLA). The prepared two-enzyme-MOF hybrid material was characterized using XRD, SEM/EDS, XPS, FT-IR, TGA, CLSM, etc. In addition, reaction kinetic studies indicated that the MOF-encapsulated two-enzyme system exhibited faster initial reaction velocities than free enzymes due to its amorphous ZIF-generated mesoporous structure. Furthermore, the pH stability and temperature stability of the biocatalyst were evaluated, and the results indicated a significant improvement compared to the free enzymes. Moreover, the amorphous structure of the mesopores still maintained the shielding effect and protected the enzyme structure from damage by proteinase K and organic solvents. Finally, the remaining activity of the biocatalyst for the synthesis of D-PLA reached 77% after 6 cycles of use, and the coenzyme regeneration still maintained at 63%, while the biocatalyst also retained 70% and 68% residual activity for the synthesis of D-PLA after 12 days of storage at 4 °C and 25 °C, respectively. This study provides a reference for the design of MOF-based multi-enzyme biocatalysts.

Identification and hepatoprotective activity of total glycosides of paeony with high content of paeoniflorin extracted from Paeonia lactiflora Pall.

The aims of this work were to obtain total glucosides of paeony (TGP) with high content of paeoniflorin and evaluate the hepo-protective properties of TGP. After optimization by response surface methodology, optimized conditions were as follows: extraction time 33.0 min, extraction temperature 48 °C, ethanol content 44%, and the yield of TGP was 47.68 mg/g. Moreover, under established macroporous resin purification, paeoniflorin content of TGP achieved 67.6% in 1.5 L scale-up verification experiment. Purified TGP (p-TGP) was further analyzed by UHPLC-Q-Orbitrap-MS/MS, and 35 compouds including paeoniflorin were identified. The obtained p-TGP effectively reduced biochemical indexes and inflammatory cytokines in liver tissue of acute alcoholic liver injury mice model. Depending on this work, TGP with definitive compound composition exhibited great protective effect against acute alcoholic liver injury in vivo. Furthermore, the finding of this work will be helpful to understand the relationship between compound composition and functional properties of Chinese herb extracts.

Osthole Alleviates D-Galactose-Induced Liver Injury In Vivo via the TLR4/MAPK/NF-κB Pathways.

Osthole, a coumarin derivative, is found in several medicinal herbs. However, the protective effects of osthole against D-galactose (D-Gal)-induced liver injury still remain unclear. In this study, osthole treatment effectively reversed D-Gal-induced liver injury, according to the results of liver HE staining, and improved ALT and AST activities. Feeding with D-Gal significantly increased MDA content, and reduced the level or activity of SOD, CAT and GSH-Px, which were all alleviated by osthole intervention. Meanwhile, osthole treatment significantly inhibited the D-Gal-induced secretion of pro-inflammatory cytokines, such as TNF-α, IL-1ß and IL-6, in both serum and liver tissue. Investigations revealed that osthole ameliorated the D-Gal-induced activation of TLR4, MYD88 and its downstream signaling pathways of MAPK (p38 and JNK) and NF-κB (nucleus p65). Therefore, osthole mediates a protective effect against D-Gal-induced liver injury via the TLR4/MAPK/NF-κB pathways, and this coumarin derivative could be developed as a candidate bioactive component for functional food.

Adsorptive removal of anionic azo dye by Al3+-modified magnetic biochar obtained from low pyrolysis temperatures of chitosan.

Magnetic γ-Fe2O3/Al3+@chitosan-derived biochar (m-Fe2O3/Al3+@CB) was prepared by introducing magnetic maghemite (γ-Fe2O3) nanoparticles and aluminum sulfate [Al2(SO4)3] into chitosan-derived biochar (CB) obtained at low pyrolysis temperatures. m-Fe2O3/Al3+@CB was used to remove typical anionic azo dye (Congo red, CR). Effects of initial CR concentration, contact time, initial pH value, background electrolytes, and temperature on CR adsorption by m-Fe2O3/Al3+@CB were studied. Compared with magnetic chitosan-derived biochar (m-Fe2O3@CB), m-Fe2O3/Al3+@CB exhibited excellent performance for a wider range of pH values (pH 1-7) and in the presence of background electrolyte. The introduction of Al3+ is an effective method for improving the properties of magnetic chitosan-derived biochar. High CR adsorption capacity (636.94 mg g-1) of m-Fe2O3/Al3+@CB could result from collaborative effect of flocculation/coagulation and electrostatic attraction. These results demonstrated that m-Fe2O3/Al3+@CB is a potential adsorbent for effective removal of organic dyes from aqueous solution due to its high adsorption capacity and convenient magnetic recovery and stronger anti-interference ability against coexisting anions in wastewater.

Construction of a red emission fluorescent probe for selectively detection of cysteine in living cells.

Cysteine (Cys) is a vital amino acid in the body, and its abnormal expression level is associated with many diseases. In this study, a novel fluorescent probe ACHB was synthesized, showing high selectivity, anti-interference ability and achieving accurate detection of cysteine. Different from most previous off-on probes, ACHB showed an on-off fluorescence response to Cys. Acrylic ester was used as a recognizer while green fluorescence protein (GFP) chromophore derivative 4-hydroxybenzylidene-imidazolinone (HBI) was used as the fluorophore. The addition of Cys leads to the hydrolysis of the red-emitting probe (613 nm), releasing a precursor with a lower fluorescent signal and showing an on-off spectral signal, which was ideal for obtaining sensitive detection with high specificity. Furthermore, the probe was successfully applied for simultaneous determination of cysteine (Cys) in living cells and biological sample (mouse serum). In conclusion, probe ACHB is a promising tool to display the intracellular cysteine concentration level, providing a good visualization method for clinical diagnosis and scientific basic research.

Magnetic Fe3O4 embedded chitosan-crosslinked-polyacrylamide composites with enhanced removal of food dye: Characterization, adsorption and mechanism.

The water solubility in acid solution, relative low adsorption capacities and unsatisfactory separation performance limit application of traditional chitosan-based adsorbents in wastewater treatment. To break the limitation, a hydrophilic magnetic Fe3O4 embedded chitosan-crosslinked-polyacrylamide composites (abbreviated as m-CS-c-PAM) were prepared by a two-step method. The m-CS-c-PAM composites were systematically characterized using SEM, XRD, FTIR, VSM, TGA and BET. Sunset yellow (SY) was selected as model food dye to investigate adsorption kinetics and thermodynamic parameters of food dye adsorption onto m-CS-c-PAM. Compared with magnetic Fe3O4/chitosan, m-CS-c-PAM can adapt to a wider range of pH (2-10) and resist the presence of inorganic salts. m-CS-c-PAM was proved to have high adsorption capacity (359.71 mg g-1) for SY dye at 298 K, much higher than magnetic Fe3O4/chitosan and many reported adsorbents. Moreover, m-CS-c-PAM could be rapidly and efficiently separated from treated solution within 15 s by an external magnet and regenerated by NaOH solution. With its excellent adsorption capacity, pH-independent adsorption capability for food dye, easy and convenient separation ability, satisfactory reusability, m-CS-c-PAM can be a promising material for food wastewater treatment.

Efficient Co-production of Docosahexaenoic Acid Oil and Carotenoids in Aurantiochytrium sp. Using a Light Intensity Gradient Strategy.

Aurantiochytrium is a promising source of docosahexaenoic acid (DHA) and carotenoids, but their synthesis is influenced by environmental stress factors. In this study, the effect of different light intensities on the fermentation of DHA oil and carotenoids using Aurantiochytrium sp. TZ209 was investigated. The results showed that dark culture and low light intensity conditions did not affect the normal growth of cells, but were not conducive to the accumulation of carotenoids. High light intensity promoted the synthesis of DHA and carotenoids, but caused cell damage, resulting in a decrease of oil yield. To solve this issue, a light intensity gradient strategy was developed, which markedly improved the DHA and carotenoid content without reducing the oil yield. This strategy produced 30.16 g/L of microalgal oil with 15.11 g/L DHA, 221 µg/g astaxanthin, and 386 µg/g ß-carotene. This work demonstrates that strain TZ209 is a promising DHA producer and provides an efficient strategy for the co-production of DHA oil together with carotenoids.

Simultaneous improvement of the thermostability and activity of lactic dehydrogenase from Lactobacillus rossiae through rational design.

d-Phenyllactic acid, is a versatile organic acid with wide application prospects in the food, pharmaceutical and material industries. Wild-type lactate dehydrogenase LrLDH from Lactobacillus rossiae exhibits a high catalytic performance in the production of d-phenyllactic acid from phenylpyruvic acid or sodium phenylpyruvate, but its industrial application is hampered by poor thermostability. Here, computer aided rational design was applied to improve the thermostability of LrLDH. By using HotSpot Wizard 3.0, five hotspot residues (N218, L237, T247, D249 and S301) were identified, after which site-saturation mutagenesis and combined mutagenesis were performed. The double mutant D249A/T247I was screen out as the best variant, with optimum temperature, t 1/2, and T 10 50 that were 12 °C, 17.96 min and 19 °C higher than that of wild-type LrLDH, respectively. At the same time, the k cat/K m of D249A/T247I was 1.47 s-1 mM-1, which was 3.4 times higher than that of the wild-type enzyme. Thus rational design was successfully applied to simultaneously improve the thermostability and catalytic activity of LrLDH to a significant extent. The results of molecular dynamics simulations and molecular structure analysis could explain the mechanisms for the improved performance of the double mutant. This study shows that computer-aided rational design can greatly improve the thermostability of d-lactate dehydrogenase, offering a reference for the modification of other enzymes.

Lactate dehydrogenase encapsulated in a metal-organic framework: A novel stable and reusable biocatalyst for the synthesis of D-phenyllactic acid.

In this study, we synthesized a novel biocatalyst by encapsulating lactate dehydrogenase (LDH) in the metal-organic framework ZIF-90 by one-pot embedding. It showed strong biological activity for efficient synthesis of D-phenyllactic acid (D-PLA). The morphology and structure of LDH@ZIF-90 was systematically characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, confocal laser scanning microscopy (CLSM) and gas sorption. According to thermogravimetric analysis (TGA), the enzyme loading of the biocatalyst was 3 %. The Michaelis-Menten constant (Km) and maximal reaction rate (Vmax) of LDH@ZIF-90 were similar to those of free LDH, which proved that ZIF-90 had good biocompatibility to encapsulate LDH. At the same time, LDH@ZIF-90 exhibited enhanced tolerance to temperature, pH and organic solvents, and its reusability was greatly improved with 68 % of initial enzyme activity remaining after 7 rounds of recylcing. Overall, LDH encapsulated in ZIF-90 may be an economically competitive and environmentally friendly novel biocatalyst for the synthesis of D-PLA.

Enhanced Antimicrobial Cellulose/Chitosan/ZnO Biodegradable Composite Membrane.

In this study, chitosan and sugarcane cellulose were used as film-forming materials, while the inorganic agent zinc oxide (ZnO) and natural compound phenyllactic acid (PA) were used as the main bacteriostatic components to fabricate biodegradable antimicrobial composite membranes. The water absorption and antimicrobial properties were investigated by adjusting the concentration of PA. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results demonstrated that the components of the composite membrane were successfully integrated. The addition of ZnO improved the mechanical and antimicrobial properties of the composite membrane, while the addition of PA with high crystallinity significantly reduced the water absorption and swelling. Moreover, the addition of 0.5% PA greatly improved the water absorption of the composite membrane. The results of antimicrobial experiments showed that PA improved the antimicrobial activity of the composite membrane against Staphylococcus aureus, Escherichia coli, Aspergillus niger and Penicillium rubens. Among them, 0.3% PA had the best antimicrobial effect against S. aureus, E. coli and A. niger, while 0.7% PA had the best antimicrobial effect against P. rubens.