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- Enhancement of bacteriocin production and antimicrobial activity of pediococcus acidilactici HA-6111-2Publication . Garcia, J. M.; Castro, S. M.; Casquete, R.; Silva, J.; Queirós, R.; Saraiva, J. A.; Teixeira, P.The effect of sequential treatments of pressure (50-150 MPa, 10 degrees C, 5 min) and temperature (57 degrees C, 15 min) on the survival and bacteriocin production of Pediococcus acidilactici HA-6111-2 cells in the exponential growth phase was assessed. The growth curves were fi tted with the modifi ed Gompertz model, and the estimated maximum specifi c growth rate was considered to be pressure dependent. A delay in the maximum value of bacteriocin production was registered for more severe pressure conditions, but it was found more notorious for pressure followed by temperature treatments. At lower pressure intensity treatment, regardless of the application order, there was an enhancement of bacteriocin production per cell when compared to the control while maintaining the maximum production value. Bacteriocin production after the treatments can be described by an exponential model.
- Bioactive polysaccharides extracts from sargassum muticumby high hydrostatic pressurePublication . Rodrigues, Dina; Freitas, Ana C.; Queirós, Rui; Rocha-Santos, Teresa A. P.; Saraiva, Jorge A.; Gomes, Ana M. P.; Duarte, Armando C.Sargassum muticum is an important source of bioactive polysaccharides; hence, high hydrostatic pressure (HHP) was used to improve their extraction efficiency. Response surface methodology and a Box-Behnken full factorial design were employed to assess and optimize the effects of extraction conditions on the yield, total sugars, total sulfated sugars and antioxidant activity of S. muticum extracts. The extraction yield ranged between 32 and 40.4% independently of the extraction conditions or seaweed solid/liquid ratio resulting in average increases of 3.6 to 4.8-fold for total sugars and sulfated sugars, as compared to conventional extraction. Extracts displayed improved antioxidant activities, yet maximum values were achieved under different optimum conditions of HHP processing, for example, 5–5.5 min, 300 MPa and 1 g of dry seaweed for yield. In conclusion, the optimal HHP technology conditions described in this paper enables to obtain enriched bioactive polysaccharide S. muticum extracts.
- Biopreservation strategies in combination with mild high pressure treatments in traditional Portuguese ready-to-eat meat sausagePublication . Castro, S. M.; Kolomeytseva, M.; Casquete, R.; Silva, J.; Queirós, R.; Saraiva, J. A.; Teixeira, P.Thrombomodulin (TM) is an endothelial cell membrane protein that acts as a major cofactor in the protein C anticoagulant pathway. The EGF-like domains 4-6 of TM (TM456) are essential for PC activation. In this study, we proposed a liposomal recombinant TM conjugate to mimic the membrane TM structure and its anticoagulant activity. First, a DSPE-PEG2000-TM456 was successfully synthesized by site-specific conjugation of azido-TM456 with DSPE-PEG2000-DBCO via copper-free click chemistry quantitatively. Then, liposome-TM456 was fabricated via direct liposome formation with the DSPE-PEG2000-TM456 and other lipids. This liposomal formulation of TM456 retained protein C activation activity as that of TM456. Also, liposome-TM456 was much more stable and had a longer plasma half-life than TM456 and DSPE-PEG2000-TM456, respectively. Moreover, liposome-TM456 showed in vivo anticoagulant effect by decreasing the mortality from 80% to 20% in a thrombin-induced thromboembolism mouse model. The reported liposome-TM456 conjugate mimics the endothelial TM anticoagulation activity and may serve as an effective anticoagulant agent candidate for future development.
- High pressure extraction of phenolic compounds from citrus peelsPublication . Casquete, R.; Castro, Sónia; Villalobos, M.C.; Serradilla, M.J.; Queirós, R.P.; Saraiva, J.A.; Córdoba, M.G.; Teixeira, PaulaThis study evaluated the effect of high pressure processing on the recovery of high added value compounds from citrus peels. Overall, the total phenolic content in orange peel was significantly (P <.05) higher than that in lemon peel, except when pressure treated at 500MPa. However, lemon peel demonstrated more antioxidant activity than orange peel. Pressure-treated samples (300 MPa, 10min; 500 MPa, 3min) demonstrated higher phenolic content and antioxidant activity comparatively to the control samples. For more severe treatments (500MPa, 10min), the phenolic content and antioxidant activity decreased in both lemon and orange peels.
- Combined effect of pediocin bacHA-6111-2 and high hydrostatic pressure to control listeria innocua in fermented meat sausagePublication . Castro, S. M.; Silva, J.; Casquete, R.; Queirós, Rui; Saraiva, J. A.; Teixeira, P.In and ex situ production of bacteriocin (bacHA-6111-2) combined with high hydrostatic pressure (300 MPa, 5 min, 10ºC) were assessed on the survival of Listeria innocua reviously inoculated in Alheira, a traditional Portuguese fermented meat product. The effect was evaluated immediately after each treatment, alone and combined, and during 60 days of storage (4ºC). For higher concentrations of L. innocua, a bacteriostatic effect was verified: i) during the first days of storage for the pressure treatment alone and in combination with ex situ production of bacteriocin; and ii) for longer periods, when pressure was combined with in situ production of bacteriocin. After this effect, the first treatments revealed rapid growth up to the initial values; while the latest treatment, and for lower initial cells, resulted in a decrease > 2 log CFU g-1, from day 3 of storage until the end of the study. A similar result was obtained for analogous pressurized L. innocua samples with ex situ production of bacteriocin. The developed work has demonstrated the potential of using the combination of natural antimicrobial compounds (pediocin bacHA-6111-2, produced either in or ex situ) with mild pressure (300 MPa, 5 min) treatments to control effectively L. innocua in fermented meat products such as Alheiras, when contaminated with values closed to the ones that might potentially arise by natural postcontamination.