Effects of Neutralization on the Physicochemical, Mechanical, and Biological Properties of Ammonium-Hydroxide-Crosslinked Chitosan Scaffolds.

It has been reported that chitosan scaffolds, due to their physicochemical properties, stimulate cell proliferation in different tissues of the human body. This study aimed to determine the physicochemical, mechanical, and biological properties of chitosan scaffolds crosslinked with ammonium hydroxide, with different pH values, to better understand cell behavior depending on the pH of the biomaterial. Scaffolds were either neutralized with sodium hydroxide solution, washed with distilled water until reaching a neutral pH, or kept at alkaline pH. Physicochemical characterization included scanning electron microscopy (SEM), elemental composition (EDX), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), and mechanical testing. In vitro cytotoxicity was assessed via dental-pulp stem cells' (DPSCs') biocompatibility. The results revealed that the neutralized scaffolds exhibited better cell proliferation and morphology. It was concluded that the chitosan scaffolds' high pH (due to residual ammonium hydroxide) decreases DPSCs' cell viability.

Biosurfactant from Bacillus subtilis DS03: Properties and Application in Cleaning Out Place System in a Pilot Sausages Processing.

Biosurfactants (BS) are amphiphilic molecules that align at the interface reducing the surface tension. BS production is developed as an alternative to synthetic surfactants because they are biodegradable, with low toxicity and high specificity. BS are versatile, and this research proposes using a biosurfactant crude extract (BCE) as part of cleaning products. This paper reported the BCE production from Bacillus subtilis DS03 using a medium with molasses. The BCE product was characterized by different physical and chemical tests under a wide pH range, high temperatures, and emulsifying properties showing successful results. The water surface tension of 72 mN/m was reduced to 34 mN/m with BCE, achieving a critical micelle concentration at 24.66 ppm. BCE was also applied to polystyrene surface as pre-treatment to avoid microbial biofilm development, showing inhibition in more than 90% of Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes above 2000 ppm BCE. The test continued using BCE as post-treatment to remove biofilms, reporting a significant reduction of 50.10% Escherichia coli, 55.77% Staphylococcus aureus, and 59.44% Listeria monocytogenes in a concentration higher than 250 ppm BCE. Finally, a comparison experiment was performed between sodium lauryl ether sulfate (SLES) and BCE (included in commercial formulation), reporting an efficient reduction with the mixtures. The results suggested that BCE is a promising ingredient for cleaning formulations with applications in industrial food applications.