Browsing by Author "Tavaria, F. K."
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- Amino acid catabolism and generation of volatiles by lactic acid bacteriaPublication . Tavaria, F. K.; Dahl, S.; Carballo, F. J.; Malcata, F. X.Twelve isolates of lactic acid bacteria, belonging to the Lactobacillus, Lactococcus, Leuconostoc, and Enterococcus genera, were previously isolated from 180- d-old Serra da Estrela cheese, a traditional Portuguese cheese manufactured from raw milk and coagulated with a plant rennet. These isolates were subsequently tested for their ability to catabolize free amino acids, when incubated independently with each amino acid in free form or with a mixture thereof. Attempts were made in both situations to correlate the rates of free amino acid uptake with the numbers of viable cells. When incubated individually, leucine, valine, glycine, aspartic acid, serine, threonine, lysine, glutamic acid, and alanine were degraded by all strains considered; arginine tended to build up, probably because of transamination of other amino acids. When incubated together, the degradation of free amino acids by each strain was dependent on pH (with an optimum pH around 6.0). The volatiles detected in ripened Serra da Estrela cheese originated mainly from leucine, phenylalanine, alanine, and valine, whereas in vitro they originated mainly from valine, phenylalanine, serine, leucine, alanine, and threonine. The wild strains tested offer a great potential for flavor generation, which might justify their inclusion in a tentative starter/nonstarter culture for that and similar cheeses. (Key words: flavor, catabolism, starter cultures, cheese)
- Antimicrobial activity of extracts from agroindustrial subproductsPublication . Moreira, D. A.; Gullon, P.; Tavaria, F. K.
- Application of chitosan in the textile industry to control microbial growthPublication . Tavaria, F. K.; Soares, J.; Oliveira, V.; Silva, R.; Morgado, J.; Malcata, F. X.; Pintado, M. E.
- Biological activities of chitin, chitosan and respective oligomersPublication . Tavaria, F. K.; Fernandes, J. C.; Santos-Silva, A.; Silva, S. Baptista da; Sarmento, B.; Pintado, M. E.Chitin and chitosan have been receiving great attention as a novel functional material for their excellent biological properties such as biodegradation, immunological, antioxidant and antibacterial activities. However, the use has been scarcely developed due to its high molecular weight, which causes poor water solubility and high viscosity of the solutions. Compared with ordinary chitosan, chitosan oligomers have much improved water-solubility and some special biological functions due to the high absorption rate at intestinal level, thus permitting its entrance in blood circulation and distribution all over the body. The potential application of chitin and chitosan, and respective oligomers, is multidimensional and it has been found in food and nutrition, biotechnology, material science, drug delivery, agriculture and environmental protection, and recently gene therapy too. In the realm of this chapter we will focus on some biological activities attributed to those molecules, such as, antimicrobial and antifungal activities, wound healing, antioxidant, anti-inflammatory, anti-carcinogenic and anti-coagulant.
- Biological properties of chitosanPublication . Tavaria, F. K.; Costa, E. M.; Gens, E. J.; Pintado, M. E.; Malcata, F. X.
- Chitosan effect upon biofilm formation of multiresistant Staphylococcus aureus strainsPublication . Costa, E. M.; Silva, S.; Tavaria, F. K.; Pintado, M. M.
- Chitosan mouthwash: toxicity and in vivo validationPublication . Costa, E. M.; Silva, S.; Costa, M. R.; Pereira, M.; Campos, D. A.; Odila, J.; Madureira, A. R.; Cardelle-Cobas, A.; Tavaria, F. K.; Rodrigues, A. S.; Pintado, M. M.A previous study showed that a chitosan mouthwash would be a valid alternative to current mouthwashesas it demonstrated, in vitro, significantly higher antibiofilm activity than two commercial mouthwashes.As such, the aim of this work was to verify the safety of the developed product and to validate, in vivo, thebiological activity ascertained in vitro. Chitosan mouthwash safety was evaluated through Ames, MTT andV79 chromosomal aberration assay while antimicrobial activity was evaluated through in vivo assays. Theresults showed that the chitosan mouthwash was safe, presenting lower cytotoxicity than a commercialmouthwash, and that it effectively reduced viable counts of Streptococcus spp. and Enterococcus spp. by ca.5.5 log of CFU. Furthermore, in direct comparison with a commercial mouthwash the chitosan mouthwashpossessed significantly higher antimicrobial activity. The conjunction of these results proves that thechitosan mouthwash is a safe, effective, natural alternative to the existent chemical mouthwashes.
- Effect of storage and lyophilization on ovine and caprine casein degradation by extracts of Cynara cardunculus (L.)Publication . Tavaria, F. K.; Sousa, M. J.; Malcata, F. X.
- Free amino acid and organic acid profile of Serpa PDO cheeses from distinct dairy industriesPublication . Araújo-Rodrigues, H.; Tavaria, F. K.; Santos, M. T.; Alvarenga, N.; Pintado, M. M.
- Insights into chitosan antibiofilm activity against methicillin-resistant Staphylococcus aureusPublication . Costa, E. M.; Silva, S.; Tavaria, F. K.; Pintado, M. M.Aims: Chitosan is a natural compound that has been validated as a viable antimicrobial agent against Staphylococcus aureus. With this work we sought to evaluate the planktonic and sessile sensitivity of methicillin-resistant S. aureus to chitosan's activity and evaluate if methicillin-resistant S. aureus (MRSA) would be more or less sensitive to chitosan's activity than methicillin-sensitive S. aureus (MSSA). Methods and Results: A group comprised of reference strains and clinical multiresistant isolates of MSSA and MRSA were used. Methicilin resistance effect upon chitosan activity was assessed in planktonic setting and in different phases of sessile colonization, namely adhesion, biofilm formation and mature biofilm through biomass and metabolism inhibition. The results obtained showed that S. aureus methicillin resistance mechanism did not impair chitosan's activity as the highest bacterial susceptibility was registered for MRSA. Chitosan was highly effective in inhibiting MSSA and MRSA strains in both planktonic and sessile settings with biofilm inhibition percentages reaching as high as 90% for MRSA. Conclusions: Staphylococcus aureus methicillin resistance did not impair chitosan's antimicrobial and antibiofilm activities and MRSA and MSSA were inhibited both in planktonic and sessile settings at low concentrations with great efficacy. Significance and Impact of the Study: Considering the obtained results chitosan shows potential as an alternative for the control of biofilm-related recalcitrant MRSA infections.