AMB Express最新文献

Cellulose, a linear glucan linked by β-1,4 glycosidic bonds, is the most abundant renewable polysaccharide on earth. Complete enzymatic hydrolysis of cellulose liberates the readily metabolizable glucose that could be further converted to valuable biocommodities, and essential to this process are cellulases that hydrolyze the β-1,4 glycosidic bonds. Cellulases are among the most intensively studied and best understood enzymes, and many key residues have been uncovered and interrogated with respect to their functions in catalysis and/or substrate binding. However, it remains to be explored whether additional residues, especially in many poorly characterized cellulases such as processive endoglucanases, might also be functionally important. Here, we investigated a processive endoglucanase from an alkaliphilic bacterium Acetivibrio alkalicellulosi AaCel5A that consists of a glycohydrolase family 5 (GH5) domain and two tandem carbohydrate-binding module family 6 (CBM6) domains. Via structure-guided engineering, we uncovered the functional importance of a previously underexplored but relatively conserved histidine (histidine70 or His⁷⁰). His⁷⁰ itself appears to be largely dispensable for hydrolyzing β-1,4 glycosidic bonds, but it is important for efficient hydrolysis of short cellodextrins such as cellotriose, cellotetraose, and cellopentaose, likely through its ability to coordinate substrate binding. Our work thus provides important mechanistic insights into how processive endoglucanases may act on short cellodextrins.

Aurantiochytrium are protists found in marine and estuarine environments, known for producing high quantities of omega-3 fatty acids, particularly docosahexaenoic acid (DHA). The commercial viability of this species is currently hindered by the lack of reliable screening methods for the rapid identification of strains with high DHA content. This study developed a high-throughput screening platform based on the sulfo-phospho-vanillin (SPV) reaction, which produces a pink chromophore upon reacting with C-C double bonds in lipids. Analysis of 200 strains derived through the UV mutagenesis of the Aurantiochytrium limacinum strain BL10 revealed 7 strains that exhibited significantly elevated SPV reactivity, compared to the naïve strain (P < 0.01). Gas chromatography-mass spectrometry analysis revealed that in 4 of the 7 strains, DHA levels were significantly higher than those of the naïve strain. Among those 4 strains, the SPV reactivity values of two strains were precisely correlated with their DHA/DPA content. The SPV reaction protocol proposed in this paper has considerable potential for the high-throughput screening of Aurantiochytrium strains particularly those derived through UV mutagenesis.

Phenolic compounds are concentrated in grape seeds; 60-70% of the extractable grape phenols are found in the seeds. The focus of this research was to isolate the phytochemicals from grape seed and to determine their ability to prevent haemolysis, their antioxidant and microbiological activities. By using the extraction procedure, three solvents were used (distilled water, ethanol and methanol). A high-performance liquid chromatographic (HPLC) test was performed to analyse the phenolic compounds and flavonoids content that were used to determine the efficiency of the various solvents used in the extraction process. All the variables under study, namely yield percentage, phenolic component concentration, and flavonoid content got significantly affected by the choice of the solvent used. The flavonoid content of the extracts was in the order methanolic extract > ethanolic extract > water extract. The methanolic extract of the grape seeds exhibited the most powerful antioxidant and hemolysis inhibitory effects among the three extracts, followed by the ethanolic and water extracts. The antibacterial activity of methanolic extract was found to be higher as compared to the ethanolic extract against Staphylococcus aureus. The antibacterial activity of the ethanolic and methanolic extracts against Salmonella enteritidis, Bacillus subtilis, Aspergillus niger and Escherichia coli were found to be equivalent. In conclusion, grape seeds contained several bioactive compounds that exerted an antioxidant, hemolysis inhibition and anti-microbial activities. These activities depends on the concentration of phenolic compounds and flavonoids in the grape seed extracts. Methanol was the superior solvent in the extraction process followed by ethanol.

Natural sweeteners have attracted widespread attention because they are eco-friendly, healthy, low in calories, and tasty. The demand for natural sweeteners is increasing together with the popularity of green, low-carbon, sustainable development. With the development of synthetic biology, microbial cell factories have emerged as an effective method to produce large amounts of natural sweeteners. This technology has significantly progressed in recent years. This review summarizes the pathways and the enzymes related to the biosynthesis of natural sweeteners, such as mogrosides, steviol glycosides, glycyrrhizin, glycyrrhetinic acid, phlorizin, trilobatin, erythritol, sorbitol, mannitol, thaumatin, monellin, and brazzein. Moreover, it focuses on the research about the microbial production of these natural sweeteners using synthetic biology methods, aiming to provide a reference for future research on the production of natural sweeteners.

One of the complication of diabetes mellitus is chronic wounds. The healing of wounds in diabetic patients is retarded by the elevation in the pro-inflammatory cytokines secretion and free radicles accumulation. Wound management in diabetic patients requires preventing bacterial biofilm development. Due to the wound healing activity of chitosan (CS), lecithin (Le) and melatonin (M), the present study aimed to load melatonin on CS/Le NPs and examine their effect on diabetic wounds infected with Staphylococcus aureus. Melatonin loaded chitosan/lecithin nanoparticles (M-CS/Le NPs) were physically characterized and their antioxidant, anti-inflammatory and antimicrobial activities were examined in vitro. Male Sprague Dawley rats included two division (non-diabetic and diabetic) which were further divided in nine groups. Diabetes induction and follow up throughout the experimental period was confirmed by measuring the levels of fructosamine and blood glucose. Full-thickness wounds was induced in both non-diabetic and diabetic animals followed by infection with Staphylococcus aureus according to the experimental design. The wound healing effect of M-CS/Le NPs was evaluated through measurements of the oxidative stress, inflammatory cytokines and apoptotic proteins. Our results showed the anti-microbial, free radical scavenging and hemolysis inhibition effects of M-CS/Le NPs in vitro. Moreover, the preparation of M-CS/Le NPs decreased the dose of used melatonin (when compared to free melatonin). M-CS/Le NPs significantly decreased the wound area percent in treated infected wounds of both non-diabetic and diabetic rats more than free melatonin or unloaded CS/Le NPs. In conclusion, M-CS/Le NPs promoted the wound healing in Staphylococcus aureus-infected wounds in diabetic rats.

African swine fever (ASF) is a contagious viral disease in pigs, caused by the African swine fever virus (ASFV). Currently, there are no effective vaccines and drugs for ASFV, making diagnostic methods crucial for the prevention and control of ASF. In this study, the ASFV p30 protein was successfully expressed using a prokaryotic expression system and used as an immunogen to prepare monoclonal antibody (mAb) 2A5. The antigenic epitope recognized by the mAb 2A5 was identified as ⁵⁸VKYDIVKSARIYAGQGY⁷⁴. Then, a blue latex microsphere immunochromatographic strip method for detecting ASFV antigens was established. Wherein a rabbit polyclonal antibody (pAb) against p30 stored in our laboratory was coupled with blue latex microspheres to prepare an immune probe, with mAb 2A5 as the test line and goat anti-rabbit IgG as the control line. The immunochromatographic strip exhibited excellent sensitivity, with a minimum detection limit of 10 ng/mL for the p30 protein. It demonstrated good specificity, showing no cross-reactivity with PRRSV, PCV2, PPV, and PEDV. Moreover, it maintained good stability and could be stored for at least 100 days at 37 °C. The concordance rate between the immunochromatographic strip and qPCR test kit was 92.2%. The immunochromatographic strip method can meet the requirements of clinical testing and provide technical support for ASFV diagnosis.

Marbled eels are migratory between freshwater, brackish, and saltwater environments. Eel mucus contains biological components that are essential in protecting against environmental pathogens. The biological activity of mucus depends on endogenous and exogenous factors. This study aimed to determine the influence of solvents in extracting bioactive compounds from marbled eel mucus for aquaculture and human healthcare applications. The results show that different solvents affect the composition and biological activity of the extract from marbled eel mucus. The extracts have 19-23 other peaks of compounds, with retention times ranging from 0.8 to 60.0 min on high-performance liquid chromatography (HPLC). The selective extraction rate of components (% area) has significant differences between extracts with different solvents. The eel mucus extracted with acetone solvent exhibited the highest biological activity in all tests: IC50 = 36.603 mg/mL and SC% = 98.424% at 100 mg/mL for antioxidant activity; Antibacterial activity was demonstrated against S. aureus (IC50 = 65.00 ± 3.01 µg/mL) and B. subtilis (IC50 = 112.00 ± 7.89 µg/mL); The ability to inhibit human skin cancer cells (IC50 = 465.96 ± 8.54 µg/mL) and normal cells (IC50 = 453.36 ± 17.88 µg/mL). Extracts extracted with n-Hexane solvent showed higher safety for cells than extracts from other solvents (IC50 = 632.43 ± 18.80 µg/mL, higher than the value IC50 = 545.25 ± 26.36 µg/mL for skin cancer cells). These results provide important data for selecting and applying products derived from extracts of marbled eel mucus in the future, sparking excitement and optimism about this research's potential impact on aquaculture and human health care.

This investigation aimed to examine the synergistic effects of fresh royal jelly and local wild Artemisia monosperma leaf extract as antibacterial, antioxidant, antibiofilm, and anti-Alzheimer activity. Gas chromatography-mass spectrometry (GC-MS) identified 16 compounds in Artemisia monosperma, including tricosadiynoic acid, hexadecenoic acid, octadecenoic acid. In contrast, fresh royal jelly contained 13 compounds, including dodecanoic acid, octadecynoic acid, hexadecenoic acid, heptatriacotanol, and their derivatives. The Artemisia monosperma extract exhibited significant antioxidant activity in the DPPH assay, with IC₅₀ value of 5.48 ± 0.002 µg/mL. Fresh royal jelly exhibited an IC₅₀ value of 14.56 ± 0.004 µg/mL. Both substances exhibited significant antibacterial activity in comparison to gentamycin. The Synergistic combination (1:1) effectively suppressed the growth of multidrug-resistant bacterial species, including Bacillus subtilis (ATCC 6633), Enterococcus faecalis (ATCC 10541), Staphylococcus aureus (ATCC 6538), Klebsiella pneumoniae (ATCC 13883), Salmonella typhi (ATCC 6539), and Pseudomonas aeruginosa (ATCC 90274), and decreased biofilm activity. Additionally, in vitro the of inhibition activity (IC₅₀) of the Butyrylcholinesterase enzyme (BChE) for the plant extract, royal jelly and the Synergistic combination were 4.35 ± 0.002 µg/mL, 4.9 ± 0.002 µg/mL, and 3.55 ± 0.002 µg/mL, respectively while the IC₅₀ of rivastigmine (positive control) was 3.9 ± 0.002 µg/mL. in silico analysis reported that the bioactive compounds demonstrated high binding affinities, between - 6.6 and - 10.3 kcal/mol, against the human acetylcholinesterase protein, beside ADMET analysis exhibited high gastrointestinal absorption and potential inhibitory effects on CYP1A2 and CYP2C9 enzymes. Our study indicated that the synergistic effect of Artemisia monosperma and royal jelly bioactive compounds exhibited a promising antibacterial, antioxidant, antibiofilm, and acetylcholinesterase inhibitory activities.

Acinetobacter baumannii is a prevalent clinical pathogen commonly found to be multidrug-resistant (MDR), causing serious to life-threatening infections, particularly hospital-acquired infections with limited therapeutic options. The MDR phenotype developed against this critical pathogen is increasingly developed globally, reaching a pan-drug-resistant phenotype conferring non-susceptibility to all antimicrobials used in its treatment according to the standard guidelines. Therefore, it is critical to develop innovative treatment approaches, such as phage therapy, considering the rise in drug-resistant A. baumannii infections. In this review, we highlight and discuss the up-to-date antimicrobial resistance of A. baumannii, the use of phages, their limitations, and future perspectives in treating A. baumannii infections. In addition, the combination of phages with antimicrobials, preclinical and clinical studies including pharmacokinetics and pharmacodynamics properties have been discussed.