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Potential use of wool-associated Bacillus species for biodegradation of keratinous materials

Publication . Queiroga, A. Catarina; Pintado, Manuela E.; Malcata, F. Xavier

Five wool-degrading bacterial strains were selected from a set of 115 isolates from a less conventional source, i.e., the wool of Portuguese Merino sheep, based on their promising keratinolytic abilities. All selected strains belong to the genus Bacillus, probably Bacillus subtilis/licheniformis, according to 16S rRNA sequencing. They were able to grow on and hydrolyse feathers and wool (in both native and milled forms), and human hair and nails to a lesser extent. The maximum keratinase activity was recorded on milled chicken feathers. Biodegradation of such keratin-rich matrices increased the amount of soluble proteins in the fermentation broth and implied the action of extracellular enzymes from those adventitious microorganisms. Therefore, such novel strains have a potential for effective use in solid waste management strategies encompassing keratin-rich materials based on submerged fermentation. Concomitantly, the nutritional value of the broth may be improved for eventual formulation of animal feed.

2012Journal article

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Chitosan: antimicrobial action upon staphylococci after impregnation onto cotton fabric

Publication . Tavaria, F.K.; Soares, J.C.; Reis, I.L.; Paulo, M.H.; Malcata, F.X.; Pintado, M.E.

Background: High levels of viable Staphylococcus aureus, which are often found on inflamed skin surfaces, are usually associated with atopic dermatitis. Textiles, owing to their high specific surface area and intrinsic hydrophilicity, retain moisture while also providing excellent environmental conditions for microbial growth and proliferation. Recently, a number of chemicals have been added to textiles, so as to confer antimicrobial activity. Aims: To evaluate the antimicrobial action of chitosan upon selected skin staphylococci. Methods and Results: We isolated staphylococci from normal skin of 24 volunteers and studied their survival upon contact with chitosan-impregnated cotton fabric. Low and high molecular weight chitosans were used at two concentrations; all four did effectively reduce the growth of some staphylococci (namely Staph. aureus), by up to 5 log cycles, thus unfolding a potential towards control and even prevention of related skin disorders. Conclusion: Our data suggest an effective, but selective antibacterial action of chitosans towards skin bacteria. Significance and Impact of the Study: The possibility to use a natural biopolymer incorporated in a textile to alleviate and even treat some of the symptoms associated with this skin condition may raise an alternative to existing medical treatments. The selectivity observed prevents full elimination of bacteria from the skin surface, which is an advantage.

2012Journal article

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Influence of abiotic factors on the antimicrobial activity of chitosan

Publication . Tavaria, Freni K.; Costa, Eduardo M.; Gens, Eduardo J.; Malcata, Francisco Xavier; Pintado, Manuela E.

In an effort to bypass the adverse secondary effects attributed to the traditional therapeutic approaches used to treat skin disorders (such as atopic dermatitis), alternative antimicrobials have recently been suggested. One such antimicrobial is chitosan, owing to the already proved biological properties associated with its use. However, the influence of abiotic factors on such activities warrants evaluation. This research effort assessed the antimicrobial activity of chitosan upon skin microorganisms (Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli) in vitro when subject to a combination of different abiotic factors such as pH, ionic strength, organic acids and free fatty acids. Free fatty acids, ionic strength and pH significantly affected chitosan's capability of reducing the viable numbers of S.aureus. This antimicrobial action was potentiated in the presence of palmitic acid and a lower ionic strength (0.2% NaCl), while a higher ionic strength (0.4% NaCl) favored chitosan's action upon the reduction of viable numbers of S.epidermidis and E.coli. Although further studies are needed, these preliminary results advocate that chitosan can in the future be potentially considered as an antimicrobial of choice when handling symptoms associated with atopic dermatitis.

2013Journal article

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