Within the last decade, pork consumption has steadily increased and continues to be the most consumed meat globally. However, pathogenic bacterial strains resistant to antibiotics have also been increasingly found in pig farms, animals, and the environment. Bacterial food poisoning cases due to Salmonella spp. and Escherichia coli (E. coli) O157:H7 appear to be linked with a variety of pork products. The meat industry has recognized that research is needed to combat the multi-drug resistance in foodborne pathogens with alternative methods of control. This study evaluated the effects of both E. coli- and Salmonella-specific lytic bacteriophages and lactic acid (LA) on E. coli O157:H7, Salmonella Enteritidis, Salmonella Montevideo, and Salmonella Heidelberg growth in raw pork loins ready for marination. The efficacy of the treatments was determined after 1 h of application and marination. Lytic bacteriophage 5% significantly (PSalmonella spp. population by 2.30 log CFU/cm2 when compared with the initial surface attachment. Moreover, the combined treatment of LA 2.5% + phage 5% significantly (PSalmonella population by 2.35 log CFU/cm2 after 1 hour of attachment. In the post-tenderization surface samples, the combination of both phage and LA showed (PP>0.05) when analyzing the translocation of Salmonella spp. on pork loins. Similar treatment efficacy results were observed in the application of E. coli O157:H7 on pork. Following antimicrobial treatments, both control and treated loin samples were enumerated after 1 h at 4°C. Both the lytic bacteriophage 5% and the combination of lytic bacteriophage 5% with lactic acid 2.5% had a significant reduction of E. coli O157:H7 on surface attachment after 1 h of treatment application. Lytic bacteriophage 5% and Lactic acid 2.5% significantly (P < 0.05) reduced the surface bacterial population by 1.89 log CFU/cm2. Lytic bacteriophage 5% alone significantly (P < 0.05) reduced the surface bacterial population by 1.90 log CFU/cm2 when compared with the initial surface attachment groups. Moreover, in the post-tenderization surface samples, lytic bacteriophage 5% and the combination of lytic bacteriophage 5% with lactic acid 2.5% were the only treatments that had a significant reduction (P < 0.05) when compared with the control group. Interestingly, lactic acid 2.5% was the only treatment that had a significant reduction (P < 0.05) of 0.76 log CFU/cm2 when analyzing the translocation of pathogens on pork chops.

The relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the  crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the conformational distortion of the α’ phase. The conformation of an α’ chain was determined to have tg’t-103 conformation with tg’t-31 units randomly distributed along the chain. Departure of the O-C α dihedral angle was also confirmed. The structural disorder leads to different thermal properties for α’ and α crystalline forms, which was quantified by measuring the enthalpic change at melting for both crystals ( = 57 ± 3 J/g and =9 6 ± 3 J/g). The transformation from α’ to α and the mechanism of order formation in PLA were also elucidated. The relationship between chain configuration of EVA random copolymers and crystallization behavior was established. For three different EVA samples, the distribution of methylene sequences was calculated and compared to a distribution of crystallite sizes formed. This comparison revealed that only a small fraction of the total methylene segments present actually crystallized. Cocrystallization with highly mobile oligomers was explored to enhance the crystallization of EVA copolymers. When blended, EVA28 (28 weight percentage) cocrystallizes with C36H74 n-alkane resulting in faster crystallization kinetics and a higher degree of crystallinity. The observed increase in degree of crystallinity was directly related to the chain configuration. Compositional mapping using Raman spectroscopy provided evidence for oligomer nucleation. The cocrystallization kinetics and morphology of EVA and n-alkane blends was found to depend on the chain length of oligomer. In both systems studied, crystallization kinetics determines the morphologies formed, which are undoubtedly related to the details of molecular architecture.

No description available.

No description available.

Yes / The shape memory effect of highly oriented long‐chain‐branched poly(lactic acid) (LCB‐PLA) prepared through solid‐phase die drawing technology was studied by comparison with PLA. When the recovery temperature increased from 60°C to 120°C, for PLA, only one‐step recovery at about 80°C can be observed and the recovery ratio was below 21.5%, while, for LCB‐PLA, multiple recovery behavior with high recovery ratio of 78.8% can be achieved. For oriented PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just free drawing; while for oriented LCB‐PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just die drawing. After shape recovery, the mechanical properties of LCB‐PLA showed a linear downward trend with the recovery temperature. Together with amorphous phase, the oriented mesomorphic phase, which formed during solid die drawing, can act as switching domains. And thus, upon heating, the chain segment of amorphous phase relaxed at first and triggered the first macroscopical shape recovery, leading to the decrease of long period (Lac) and the thickness of the amorphous layer (La). Then, with further increasing temperature, the oriented mesomorphic phase gradually relaxed resulting subsequently multi‐shape recovery, and the Lac and the La further decreased. Therefore, by regulating the recovery temperature of oriented LCB‐PLA, the shape recovery ratio and mechanical strength can be controlled effectively, and thus the self‐reinforced and self‐fastening effect can be achieved simultaneously for PLA as bone fixation material.

This research is the first systematic investigation of solid-state orientation as a novel method for controlling drug release from biodegradable polymers. The effect of various degrees of polymer orientation was studied in oriented Poly (L-lactic acid) (PLA) films containing curcumin and theophylline as model drugs. Additionally, direction specific drug release was studied from oriented PLA rods containing paracetamol. The films oriented to 2X uniaxial constant width (UCW) or 2X2Y biaxial draw ratio showed retardation of drug release, when their nematic structure was stabilised by the presence of crystalline theophylline. Contrarily, the same films when contained solid solution of curcumin, shrunk in the release medium and exhibited a release profile similar to the un-oriented films. All films oriented to the UCW draw ratio ≥ 3X contained α crystalline form of PLA and showed acceleration of drug release proportionate to the draw ratio. According to the proposed mechanism augmented formation of water filled channels in these films was responsible for faster drug release. Similarly, the paracetamol loaded PLA rods die-drawn to uniaxial draw ratios ≥ 3X exhibited enhancement of drug release. Importantly, the amount of drug released along the oriented chain axis was significantly larger than that in the perpendicular direction. Drug release from the die-drawn rods was accelerated by a greater degree than that observed from the oriented films. This can be correlated to the differences in their size, geometry and the crystalline form of PLA. In conclusion, the current study provided substantial evidence that solid-state orientation can offer a control over drug release from PLA.

RESUMEN El objetivo de esta tesis fue la obtención y caracterización de films biodegradables con características antimicrobianas y/o antioxidantes a partir de quitosano (CH). Para modular sus propiedades y mejorar su funcionalidad, se estudió la combinación con otras matrices poliméricas: almidón de trigo (WS), polivinil alcohol (PVA) y ácido poliláctico (PLA). Además se incorporaron aceites esenciales (EO) de tomillo (Th) o albahaca (B), ¿-tocoferol (Tp) y ácido cítrico (CA). Se evaluó el efecto del tratamiento de homogenización de las dispersiones formadoras de films (FFD) en films de quitosano con EO en diferentes proporciones. La microfluidización dio lugar a una reducción en el tamaño de gota, a una mayor carga superficial de las mismas y una menor viscosidad de las dispersiones. Además, intensificó todos los efectos provocados por la incorporación de EO sobre las propiedades mecánicas de los films debido a potenciación de las interacciones con el polímero. A baja proporción de EO, la microfluidización mejoró las propiedades de barrera al vapor de agua de los films, pero no tuvo un impacto significativo en la permeabilidad al oxígeno. Los films ejercieron un papel protector frente a la oxidación en grasa de cerdo. La presencia de EO en los films, a pesar de aumentar la permeabilidad al oxígeno, dio lugar a una menor velocidad de oxidación de las muestras (especialmente a alta humedad relativa), probablemente por el efecto antioxidante de los componentes de los EO. Los films de quitosano se mostraron efectivos en el control del deterioro microbiano cuando se aplicaron en carne de cerdo picada, pero la incorporación de los EO no mejoró su actividad antimicrobiana. Se incorporó CH en films de WS en diferentes proporciones. La adición de CH en cantidades crecientes dio lugar a un aumento en la viscosidad y estabilidad de las FFD. Ambos polímeros mostraron un alto grado de compatibilidad lo que dio lugar a una microestructura homogénea. El aumento de la proporción de CH dio lugar a films con mejores propiedades mecánicas ya que el CH pareció inhibir la retrogradación del almidón. Los films WS:CH dieron lugar a una reducción de la carga microbiana cuando se aplicaron en muestras de carne de cerdo picada. Se incorporaron diferentes antioxidantes (aceite esencial de tomillo y albahaca, ácido cítrico y ¿-tocoferol) en films mezcla de WS (80%) y CH (20%). Los films presentaron una microestructura heterogénea por la inmiscibilidad de componentes, principalmente el film con ¿-tocoferol que presentó separación de fases. Esto llevó asociado una superficie más rugosa, con menor brillo y, en el caso del ¿-tocoferol, un color más amarillo. No obstante la incorporación de antioxidantes conllevó un aumento de la transparencia y una disminución de la permeabilidad al oxígeno. El CA provocó un aumento en el módulo de elasticidad y un descenso de la extensibilidad de los films. La incorporación de CH en matrices de PVA dio lugar a films altamente homogéneos, debido a la compatibilidad de ambos polímeros. Se obtuvieron films más resistentes y rígidos, pero menos extensibles. Se observó una reducción del grado de cristalinidad y un aumento de la estabilidad térmica, además de una reducción de la trasmisión de la luz UV. Así mismo, cuando se aplicaron a muestras de carne de cerdo picada presentaron una acción antimicrobiana. La incorporación de CH en una matriz de PLA mediante extrusión no afectó al comportamiento térmico del PLA ni a su grado de cristalinidad. Ambos polímeros se mostraron incompatibles. La reducción del tamaño de las partículas de CH minimizó el impacto negativo sobre las propiedades mecánicas y de barrera al vapor de agua. En su aplicación a muestras de carne de cerdo picada, la presencia de CH mejoró las propiedades antimicrobianas de los films. / Bonilla Lagos, MJ. (2013). Desarrollo de films y recubrimientos comestibles bio-activos como soporte de agentes antioxidantes y antimicrobianos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28370

Tesis por compendio / [EN] The current PhD thesis deals with the development and characterization of novel nanocomposites based on biodegradable poly(mannitol sebacate) (PMS) matrices with tailored properties and shape-memory capabilities for biomedical applications. Two types of fillers -cellulose nanocrystals (CNC) and electrospun poly(lactic acid) nanofibers (NF-PLA)- were used as reinforcement in order to induce and/or enhance the shape-memory properties of PMS matrices. Also, different crosslinking profiles and stoichiometric ratios between mannitol and sebacic acid (1:1 and 1:2) were studied and evaluated to obtain samples with low and high degrees of crosslinking. An appropriate combination of the crosslinking profile and the monomer ratio for PMS matrix, as well as the addition of low content of CNC, allowed the development of PMS/CNC nanocomposites with a wide range of mechanical properties and degradation profiles. On the other hand, highly oriented poly(lactic acid) (PLA) nanofiber mats obtained by electrospinning were embedded in the PMS matrices. An enhancement of up to 53-fold in the Young's modulus was observed for PMS/NF-PLA nanocomposites filled with 15 wt% of PLA nanofibers. The incorporation of fillers (CNC and NF-PLA) allowed the development of thermally active shape-memory nanocomposites with an enhancement of parameters such as recovery stress and shape fixity. The electrospun PLA-reinforced nanocomposites, offered the best balance of mechanical and thermal properties, as well as a greater control of the transition temperature for switching the change of shape, within a useful range of temperatures. Owing to that, these materials may be of interest as smart responsive systems in long-term biomedical applications. / [ES] La presente tesis doctoral, se centra en el desarrollo y caracterización de nuevos nanocompuestos biodegradables, a partir de matrices de poli(mannitol sebacato) (PMS) con propiedades a medida y capacidades de memoria de forma para aplicaciones biomédicas. Dos tipos de cargas -nanocristales de celulosa (CNC) y nanofibras de ácido poliláctico (NF-PLA) obtenidas mediante electrospinning- se han utilizado como refuerzo, con la finalidad de inducir y/o mejorar las propiedades de memoria de forma en matrices de PMS. Se han estudiado y evaluado diferentes tratamientos de curado y ratios de reacción entre el mannitol y ácido sebácico (1:1 y 1:2), con la finalidad de obtener muestras con bajo y alto grado de reticulación. Una combinación adecuada del tratamiento de curado y el ratio entre monómeros del PMS, así como la adición de bajos contenidos de CNC, permitió desarrollar nanocompuestos de PMS/CNC con un amplio rango de propiedades mecánicas y perfiles de degradación. Por otro lado, se han producido mats de nanofibras de ácido poliláctico (PLA) con alta orientación mediante la técnica de electrospinning, para embeberse en matrices de PMS, observándose una mejora de hasta 53 veces en el módulo de Young para nanocompuestos de PMS/NF-PLA con un 15% en peso de nanofibras. La incorporación de cargas (CNC y NF-PLA) permitió el desarrollo de nanocompuestos con memoria de forma activada térmicamente, con una mejora de parámetros tales como la fuerza de recuperación y la capacidad de fijación. Los nanocompuestos reforzados con NF-PLA obtenidas por electrospinning, ofrecieron el mejor balance de propiedades mecánicas y térmicas, así como un mayor control de la temperatura de transición para la activación del cambio de forma en un intervalo útil de temperaturas. Por todo ello, estos materiales pueden resultar de interés como sistemas activos en aplicaciones biomédicas de larga duración. / [CA] La present tesi doctoral se centra en el desenvolupament i caracterització de nous nanocompostos biodegradables a partir de matrius de poli(mannitol sebacato) (PMS) amb propietats a mesura i capacitats de memòria de forma per a aplicacions biomèdiques. Dos tipus de càrregues -nanocristals de cel·lulosa (CNC) i nanofibres d'àcid polilàctic (NF-PLA) obtingudes mitjançant electrospinning- s'han utilitzat com a reforç amb la finalitat d'induir i/o millorar les propietats de memòria de forma en matrius de PMS. S'han estudiat i avaluat diferents tractaments de curat i ràtios de reacció entre el mannitol i àcid sebàcic (1:1 i 1:2) amb la finalitat d'obtenir mostres amb baix i alt grau de reticulació. Una combinació adequada del tractament de curat i el ràtio entre monòmers del PMS, així com l'addició de baixos continguts de CNC, va permetre desenvolupar nanocompostos de PMS/CNC amb un ampli rang de propietats mecàniques i perfils de degradació. D'altra banda, s'han produït mats de nanofibres d'àcid polilàctic (PLA) amb alta orientació mitjançant la tècnica de electrospinning, per embeure's en matrius de PMS, observant-se una millora de fins a 53 vegades en el mòdul de Young per nanocompostos de PMS/NF-PLA amb un 15% en pes de nanofibres. La incorporació de càrregues (CNC i NF-PLA) va permetre el desenvolupament de nanocompostos amb memòria de forma activada tèrmicament, amb una millora de paràmetres tals com la força de recuperació i la capacitat de fixació. Els nanocompostos reforçats amb NF-PLA obtingudes per electrospinning, van oferir el millor balanç de propietats mecàniques i tèrmiques, així com un major control de la temperatura de transició per a l'activació del canvi de forma en un interval útil de temperatures. Per tot això, aquests materials poden resultar d'interés com a sistemes actius en aplicacions biomèdiques de llarga durada. / Sonseca Olalla, A. (2015). DEVELOPMENT OF SHAPE-MEMORY COMPOSITES BASED ON A BIODEGRADABLE POLYESTER ELASTOMER [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54129 / Compendio

La sicurezza e la qualità degli alimenti sono tutt’ora un problema critico per i paesi in via di sviluppo. Le diete a basso contenuto di acido folico, per esempio, possono causare gravi problemi di salute, soprattutto nei bambini. Gravi disturbi legati al tubo neurale (DTN) nei neonati possono derivare infatti da madri che hanno insufficiente apporto di acido folico (400-600 g / giorno) durante il periodo di gravidanza. Inoltre, se non adeguatamente protetti o trattati, I prodotti alimentari possono essere vettori di funghi e batteri patogeni rappresentando una fonte potenziale di malattie per l’uomo e una perdita economica per le industrie agro-alimentari. Nella seguente tesi si è quindi quindi studiato il ruolo di batteri lattici selezionati (LAB) in grado di aumentare il valore nutrizionale del latte attraverso la produzione di acido folico durante il processo di fermentazione. Inoltre, ci si è concentrati sul loro uso come "bio-conservanti" contro funghi e batteri, attraverso la sintesi di composti antimicrobici (batteriocine) in grado di inibire la crescita di funghi filamentosi e/o batteri patogeni. / The safety and quality of food are still a critical issue in developing countries. Diets with a low content of folic acid, for example, may cause serious health problems, especially in children. Severe disorders related to neural tube (NTD) in infants may arise from mothers having inadequate intakes of folic acid (400-600 g/dia) during the mother pregnancy period. Moreover foods, when not properly protected or treated, can be vectors of pathogenic fungi and bacteria thereby representing a potential source of human diseases and an economical loss for the food industry. In the following thesis we have therefore investigated the role of selected lactic acid bacteria (LAB) in increasing the nutritional value of milk through the production of folic acid during the fermentation process. In addition, we focused on their use as “bio-preservatives” against fungal and bacterial spoilage, through the synthesis of antimicrobial compounds (bacteriocins) able to inhibit the growth of filamentous fungi and /or pathogenic bacteria.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The equine gastro-intestinal tract (GIT) is a relatively unexplored niche concerning the presence of natural microbiota. Studies have shown that disruption of the microbial population naturally present in the GIT leads to the onset of several forms of gastro-intestinal disorders. To maintain a balanced microbiota, probiotic bacteria need to be administered at specific levels. Beneficial microorganisms assist with digestion of the feed, absorption of nutrients from the GIT, strengthens the immune system and improves the animal‟s growth. Various combinations of lactic acid bacteria (LAB) have been administered to horses, but have failed to benefit the host in any of the latter criteria. The screening for alternative strains with probiotic properties is thus necessary. Two strains (Lactobacillus equigenerosi Le1 and Lactobacillus reuteri Lr1) were originally isolated from horse faeces. Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA, both bacteriocin-producing strains, were isolated from sorghum beer and soy beans, respectively. All four strains survived growth at acidic conditions (pH 3) and the presence of 0.5%, 1.0% and 1.5% (w/v) bile salts. L. reuteri Lr1 was the most resistant to these conditions. All strains adhered to buccal (cheek) epithelium cells sampled from horses. L. equigenerosi Le1 and E. mundtii ST4SA, however, invaded the cells, but without visible signs of disrupting the cells. None of the strains contained genes encoding adhesion to collagen (Ace), resistance to vancomycin A, B and C, or, production of aggregation substance (AS), cytolysin (Cyl) and, non-cytolysin (β hemolysin III), suggesting that they are non-virulent. Of all strains, L. equigenerosi Le1 competed the best with Clostridium sp. C6 for adherence to epithelial cells. L. equigenerosi Le1 and L. reuteri Lr1, showed the highest level of co-aggregation with Clostridium sp. C6. When the four strains were administered to horses over a period of 10 days, L. reuteri Lr1 was retained the longest (8 days) in the GIT. The numbers of viable cells of Clostridium spp. and Salmonella spp. remained constant during administration of the four strains. Blood analyses showed no negative effects from administering the strains. Total white blood cell counts remained unchanged. However, a small but tentative increase in neutrophil and eosinophil cell numbers has been recorded, suggesting that the LAB may have elicited a mild, transient, intolerance reaction. The glucose, lactate and urea levels decreased during administration with the four LAB strains. / AFRIKAANSE OPSOMMING: Die spysverteringstelsel (SVS) van die perd is 'n relatief onbekende nis wat die voorkoms van natuurlike mikrobiota betref. Studies het getoon dat versteuring van die natuurlike mikrobiese populasie in die SVS aanleiding kan gee tot die ontwikkeling van menige vorms van gastro-intestinale ongesteldhede. Om 'n gebalanseerde mikrobiota te verseker, moet probiotiese bakterieë teen 'n spesifieke vlak toegedien word. Voordelige mikroorganismes bevorder vertering en absorpsie van nutriënte vanaf die SVS, versterk die immuunsisteem en bevorder die groei van die dier. Verskeie kombinasies van melksuurbakterieë is reeds aan perde toegedien, maar sonder ooglopende voordele vir die dier. Die soeke na alternatiewe stamme met probiotiese eienskappe is dus noodsaaklik. Twee melksuurbakterieë (Lactobacillus equigenerosi Le1 en Lactobacillus reuteri Lr1) is oorspronklik uit perdemis geïsoleer. Lactobacillus plantarum 423 en Enterococcus mundtii ST4SA, beide bakteriosienproduserende stamme, is afsonderlik van sorghumbier en sojabone geïsoleer. Al vier spesies groei by lae pH (pH 3) en in die teenwoordigheid van 0.5%, 1.0% en 1.5% (m/v) galsoute. L. reuteri Lr1 is die mees bestand onder hierdie toestande. Al vier stamme het aan wang epiteelselle van perde geheg. L. equigenerosi Le1 en E. mundtii ST4SA het egter die epiteelselle binnegedring, maar sonder opsigtelike vernietiging van die selle. Nie een van die stamme besit gene wat kodeer vir aanhegting aan kollageen (Ace), bestandheid teen vankomisien A, B en C, of produksie van, sel-aggregasie (AS), sitolisien (Cyl) en nie-sitolisien (β-hemolisien III), wat daarop dui dat hulle nie-virulent is. Van al die stamme het L. equigenerosi Le1 die beste met Clostridium sp. C6 vir aanhegting aan epiteelselle gekompeteer. L. equigenerosi Le1 en L. reuteri Lr1, het die beste vlak van ko-aggregasie met Clostridium sp. C6 getoon. Met die toediening van 'n kombinasie van die vier stamme aan die perde oor 'n periode van 10 dae, het L. reuteri Lr1 die langste retensie (8 dae) in die SVS getoon. Die aantal lewende selle van Clostridium spp. en Salmonella spp. het konstant gebly tydens toediening van die vier stamme. Toediening van die vier stamme het geen negatiewe effek getoon met resultate verkry van bloed analises nie. Die totale witbloed seltellings het onveranderd gebly. 'n Klein, maar tentatiewe, toename in neutrofiel- en eosinofiel selgetalle is waargeneem, wat daarop dui dat die melksuurbakterieë 'n geringe allergiese reaksie teweeggebring het. Die glukose, laktaat en ureum vlakke het gedaal tydens die toediening van die vier melksuurbakterie stamme.