Manuel Horue

Organoclays were prepared using Argentinean montmorillonite (Mt), hexadecyltrimethylammonium, or benzalkonium chloride at different concentrations. Surfactant incorporation, a key factor in biocide capacity, was estimated using interlayer space and thermogravimetric analysis (TGA). Subsequently, Fe oxides were grown on the organoclays. Saturation magnetization indicated that all magnetic composites could respond to an external magnetic field. Inhibition experiments showed high antibacterial activity against Enterococcus faecium , Escherichia coli , and Salmonella typhimurium . The synthesized nanocomposites loaded with 150% CEC (cation exchange capacity) of hexadecyltrimethylammonium were the most effective. Those results were more precisely investigated using the viable plate count method. The magnetic materials had a similar antimicrobial effect to those without magnetic properties, indicating that Fe oxides can be nucleated to impart a magnetic response without affecting the biocide properties. The organoclays showed higher antibacterial activity against E. coli than against the other bacteria assayed. In addition, the agar disk-diffusion method revealed that antimicrobial agents were not released from clays, which is a relevant fact in the water treatment process.

Bacterial cellulose (BC) is produced by several microorganisms as extracellular structures and can be modified by various physicochemical and biological strategies to produce different cellulosic formats. The main advantages of BC for biomedical applications can be summarized thus: easy moldability, purification, and scalability; high biocompatibility; and straightforward tailoring. The presence of a high amount of free hydroxyl residues, linked with water and nanoporous morphology, makes BC polymer an ideal candidate for wound healing. In this frame, acute and chronic wounds, associated with prevalent pathologies, were addressed to find adequate therapeutic strategies. Hence, the main characteristics of different BC structures—such as membranes and films, fibrous and spheroidal, nanocrystals and nanofibers, and different BC blends, as well as recent advances in BC composites with alginate, collagen, chitosan, silk sericin, and some miscellaneous blends—are reported in detail. Moreover, the development of novel antimicrobial BC and drug delivery systems are discussed.

The antibiotic norfloxacin was adsorbed on clay and carbon-clay nanocomposites (MD-210 and MDac3-210-500, synthesized by hydrothermal carbonization of dextrose) but maintained its antimicrobial activity once adsorbed. To degrade it, direct (DP) and indirect (IP, with sulfate radicals) photolysis were performed. Antimicrobial activity tests were performed to evaluate the degradation generated. There were no significant differences between DP and IP for unabsorbed norfloxacin solution. The IP treatment caused a loss of antibiotic activity in all cases. For DP, the carbon samples showed better results than those of clay, evidencing the importance of oxygenated carbonaceous groups in the photolysis of norfloxacin.

BACKGROUND: Recycling food wastes into high‐value‐added products not only impacts beneficially on the environment but also on local economies. Mango wastes represent more than 92 000 tons per year in Peru. Bioconversion of mango waste into bacterial cellulose (BC) can provide valuable products in biomedicine.RESULTS: Screening of BC producers in kombucha tea allows the selection of wild‐type strains. One of the selected wild‐type strains, named SU12, was cultured in batch using Hestrin–Schramm (HS) synthetic medium under static conditions and was able to produce a membrane in the liquid–air interface. The membrane was purified and characterized by chemical (Congo red), spectroscopic (Fourier transform infrared), thermogravimetric analysis and differential scanning calorimetric techniques as BC. The strain SU12 was tested using chemical and molecular techniques (16S rRNA) and identified phylogenetically as Komagataeibacter rhaeticus SU12 with 99.85% similarity and 96.5/1/98 values of Shimodaira–Hasegawa approximate similarity test/aBayes/bootstrap analyses. HS medium supplemented with mango extracts was optimized using Plackett–Burmann's design followed by factorial design of relevant parameters and adjusted by regression to a first‐order polynomial equation. Optimized major parameters of mango extract, yeast extract, ethanol concentration and incubation time produced 25.34 g L⁻¹ dry cellulose in 21 days.CONCLUSIONS: The study demonstrated the isolation of wild‐type strain identified as K. rhaeticus SU12 capable of producing BC using synthetic medium supplemented with extracts of mango wastes and high BC production comparable with other members of the same species. © 2021 Society of Chemical Industry (SCI).