Antioxidant and Anticoagulant Activity of Microbial Nano Cellulose-ZnO-Ag Composite Components.

<b>Background and Objectives:</b> Bacterial cellulose (BC) is a microbial extracellular biopolymer formed by microbial strains like <i>Gluconacetobacter xylinus</i>. The objective of this study was to determine the antioxidant and anticoagulant of a microbial nano cellulose-ZnO-Ag (CNCs) composite and its components separately. <b>Materials and Methods:</b> Three components were used for nano cellulose-ZnO-Ag composite synthesis, Ag-nanoparticles, ZnO-nanoparticles and BC. The DPPH method was used to calculate the scavenging of free radical behaviour of four different composite samples. <b>Results:</b> Results of silver nanoparticles were found to have the highest antioxidant activity with IC₅₀ 65 µg mL¹, followed by CNCs-ZnO-Ag composite (IC₅₀ 88.98 µg mL¹) but ZnONPs IC₅₀ was 263 µg mL¹ and BC (IC₅₀ 955 µg mL¹). The CNCs-ZnO-Ag composite, BC and AgNPs at 25 µg mL¹ had clotting times that were nearly identical to the control. The APTT increased to 56 Sec at 75 µg mL¹ of CNCs-ZnO-Ag composite related to control that recorded 33 Sec. <b>Conclusion:</b> Bacterial cellulose acquired new activity in nano form and also when conjugated with nanoparticles. The CNCs-ZnO-Ag composite is ready for pharmaceutical application as an antioxidant and anticoagulant after <i>in vivo</i> study.

Stable, efficient, and cost-effective system for the biosynthesis of recombinant bacterial cellulose in Escherichia coli DH5α platform.

BACKGROUND: Owing to its remarkable mechanical properties that surpass the plant-based cellulose, bacterial cellulose production has been targeted for commercialization during the last few years. However, the large-scale production of cellulose is generally limited by the slow growth of producing strains and low productivity which ultimately makes the commercial production of cellulose using the conventional strains non cost-effective. In this study, we developed a novel plasmid-based expression system for the biosynthesis of cellulose in E. coli DH5α and assessed the cellulose productivity relative to the typically used E. coli BL21 (DE) expression strain. RESULTS: No production was detected in BL21 (DE3) cultures upon expression induction; however, cellulose was detected in E. coli DH5α as early as 1 h post-induction. The total yield in induced DH5α cultures was estimated as 200 ± 5.42 mg/L (dry weight) after 18 h induction, which surpassed the yield reported in previous studies and even the wild-type Gluconacetobacter xylinum BRC5 under the same conditions. As confirmed with electron microscope micrograph, E. coli DH5α produced dense cellulose fibers with ~ 10 µm diameter and 1000-3000 µm length, which were remarkably larger and more crystalline than that typically produced by G. hansenii. CONCLUSIONS: This is the first report on the successful cellulose production in E. coli DH5α which is typically used for plasmid multiplication rather than protein expression, without the need to co-express cmcax and ccpAx regulator genes present in the wild-type genome upstream the bcs-operon, and reportedly essential for the biosynthesis.

Antimicrobial Profile of Actinomycin D Analogs Secreted by Egyptian Desert Streptomyces sp. DH7.

Egyptian deserts are an underexplored ecological niche, especially the Sinai Peninsula. In our recent study, we explored this extreme environment and shed light on the bioactive capabilities of desert Actinobacteria isolated from Sinai. Fifty desert Actinobacteria were isolated from the Sinai desert using mineral salt media, basal media, and starch casein media. The filtrate of Streptomyces sp. DH 7 displayed a high inhibitory effect against multidrug-resistant Staphylococcus aureus (MRSA) strains. The 16S rDNA sequencing confirmed that isolate DH7 belongs to the genus Streptomyces. The NJ phylogenetic tree showed relatedness to the Streptomyces flavofuscus strain NRRL B-2594 and Streptomyces pratensis strain ch24. The minimum inhibitory concentrations against MRSA were 16 and 32 µg/µL. Chemical investigation of the ethyl acetate extract of Streptomyces sp. DH7 led to the isolation and purification of natural products 1-4. Structure elucidation of the purified compounds was performed using detailed spectroscopic analysis including 1 and 2D NMR, and ESI-MS spectrometry. To the best of our knowledge, this is the first report for the isolation of compounds 1-4 from a natural source, while synthetic analogs were previously reported in the literature. Compounds 3-4 were identified as actinomycin D analogues and this is the first report for the production of actinomycin D analogs from the Sinai desert with an inhibitory effect against MRSA. We indorse further study for this analog that can develop enhanced antimicrobial activities. We confirm that the desert ecosystems in Egypt are rich sources of antibiotic-producing Actinobacteria.