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Hydrodynamic cavitation treatment was used for the functional inactivation of quorum-sensing lactone molecules of Pseudomonas aeruginosa. Hydroxyl radicals formed as well as the shear effects during the cavitation process induced the inactivation of the signal molecules through hydrolysis reaction coupled with bacterial destruction. Concentration of two different types of homoserine lactones (HSL) molecules was tested after the treatment at various rotational speeds. It was found that the strongest effects can be achieved at speeds > 2000 rpm. This value is considered as an onset speed of dominant cavitation, and it is in agreement with literature data. The experimental trends were in agreement with the calculations based on the finite element modelling, which show a significant increase in average shear stress at higher rotational speeds. Overall, the work has demonstrated the possible effects of hydrodynamic cavitation on the quorum-sensing molecules of Pseudomonas aeruginosa for the first time.

In this study, a carboxyl-modified cellulosic hydrogel was developed as the base material for wound dressings. ε-poly-l-lysine, a natural polyamide, was then covalently linked to the hydrogel through a bioconjugation reaction, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). The antibacterial efficacy of the hydrogel was tested against two model bacteria, Staphylococcus aureus and Pseudomonas aeruginosa , two of the most commonly found bacteria in wound infections. Bacterial viability and biofilm formation after exposure of bacteria to the hydrogels were used as efficacy indicators. Live/Dead assay was used to measure the number of compromised bacteria using a confocal laser scanning microscope. The results show that the antibacterial hydrogel was able to kill approximately 99% of the exposed bacteria after 3 h of exposure. In addition, NIH/3T3 fibroblasts were used to study the biocompatibility of the developed hydrogels. Water-soluble tetrazolium salt (WST)-1 assay was used to measure the metabolic activity of the cells and Live/Dead assay was used to measure the viability of the cells after 24, 48, and 72 h. The developed antibacterial hydrogels are light weight, have a high water-uptake capacity, and show high biocompatibility with the model mammalian cells, which make them a promising candidate to be used for wound dressing applications.

Anthropogenic activities have increased the amount of urban wastewater discharged into natural aquatic reservoirs containing a high amount of nutrients such as phosphorus (Pi and PO 4 - 3 ), nitrogen (NH 3 and NO 3 - ) and organic contaminants. Most of the urban wastewater in Mexico do not receive any treatment to remove nutrients. Several studies have reported that an alternative to reduce those contaminants is using consortiums of microalgae and endogenous bacteria. In this research, a genome-scale biochemical reaction network is reconstructed for the co-culture between the microalga Chlorella vulgaris and the bacterium Pseudomonas aeruginosa . Metabolic Pathway Analysis (MPA), is applied to understand the metabolic capabilities of the co-culture and to elucidate the best conditions in removing nutrients. Theoretical yields for phosphorus removal under photoheterotrophic conditions are calculated, determining their values as 0.042 mmol of PO 4 - 3 per g DW of C. vulgaris , 19.43 mmol of phosphorus (Pi) per g DW of C. vulgaris and 4.90 mmol of phosphorus (Pi) per g DW of P. aeruginosa . Similarly, according to the genome-scale biochemical reaction network the theoretical yields for nitrogen removal are 10.3 mmol of NH 3 per g DW of P. aeruginosa and 7.19 mmol of NO 3 - per g DW of C. vulgaris . Thus, this research proves the metabolic capacity of these microorganisms in removing nutrients and their theoretical yields are calculated.

Nanocellulose from wood is a novel biomaterial, which is highly fibrillated at the nanoscale. This affords the material a number of advantages, including self-assembly, biodegradability and the ability to absorb and retain moisture, which highlights its potential usefulness in clinical wound-dressing applications. In these in vitro studies, the wound pathogen Pseudomonas aeruginosa PAO1 was used to assess the ability of two nanocellulose materials to impair bacterial growth (<48 h). The two nanocelluloses had a relatively small fraction of residual fibres (<4%) and thus a large fraction of nanofibrils (widths <20 nm). Scanning electron microscopy and confocal laser scanning microscopy imaging demonstrated impaired biofilm growth on the nanocellulose films and increased cell death when compared to a commercial control wound dressing, Aquacel(®). Nanocellulose suspensions inhibited bacterial growth, whilst UV-vis spectrophotometry and laser profilometry also revealed the ability of nanocellulose to form smooth, translucent films. Atomic force microscopy studies of the surface properties of nanocellulose demonstrated that PAO1 exhibited markedly contrasting morphology when grown on the nanocellulose film surfaces compared to an Aquacel(®) control dressing (p<0.05). This study highlights the potential utility of these biodegradable materials, from a renewable source, for wound dressing applications in the prevention and treatment of biofilm development., (Copyright © 2015 Elsevier Ltd. All rights reserved.)