In recent years, a strong interest has emerged in hybrid composites and their potential uses, especially in chitosan-titanium dioxide (CS-TiO 2 ) composites, which have interesting technological properties and applications. This review describes the reported advantages and limitations of the functionalization of chitosan by adding TiO 2 nanoparticles. Their effects on structural, textural, thermal, optical, mechanical, and vapor barrier properties and their biodegradability are also discussed. Evidence shows that the incorporation of TiO 2 onto the CS matrix improves all the above properties in a dose-dependent manner. Nonetheless, the CS-TiO 2 composite exhibits great potential applications including antimicrobial activity against bacteria and fungi; UV-barrier properties when it is used for packaging and textile purposes; environmental applications for removal of heavy metal ions and degradation of diverse water pollutants; biomedical applications as a wound-healing material, drug delivery system, or by the development of biosensors. Furthermore, no cytotoxic effects of CS-TiO 2 have been reported on different cell lines, which supports their use for food and biomedical applications. Moreover, CS-TiO 2 has also been used as an anti-corrosive material. However, the development of suitable protocols for CS-TiO 2 composite preparation is mandatory for industrial-scale implementation.Materials 2020, 13, 811 2 of 27 they are synthesized by different methods (intercalation of the polymer, sol-gel, hydrothermal, electro-deposition, chemical and physical vapor deposition, suspension and liquid phase deposition). These methods are effective to enhance the technological and mechanical properties of each individual component and also reveal new functionalities [1,3]. Currently, there is a special interest in combining natural polymers such as chitosan (CS) with inorganic materials like titanium dioxide (TiO 2 ) to obtain hybrid composites (CS-TiO 2 ) with beneficial properties [3][4][5][6].Chitosan (CS) is a natural biopolymer (linear polysaccharide comprising 1-4 linked 2-amino-deoxy-β-D-glucan) generally obtained by deacetylation of chitin, the main structural component of crustacean exoskeletons. CS exhibits a poly-cationic character and is non-toxic and biodegradable [7]. CS is considered a biological functional compound with multiple interesting properties. It can form films for food and pharmaceutical applications, including edible coatings, packaging material, or as drug-eluting carrier [5,7]. Its adsorbent capacity can have environmental applications during photocatalytic processes of waste-water treatment [8], and it also has inherent antibacterial and antifungal properties [9]. It is biocompatible with several organic and inorganic compounds by the presence of free amino and hydroxyl functional groups in its structure, which can react with other functional groups by electrostatic forces, hydrogen bonds, or by compound-soak up into the polymeric matrix, thus improving its mechanical and biological properties [10]...

In recent years, a strong interest has emerged in polysaccharide-hybrid composites and their potential applications, which have interesting functional and technological properties. This review summarizes and discusses the reported advantages and limitations of the functionalization of conventional and nonconventional polysaccharides by adding TiO2 nanoparticles as a reinforcement agent. Their effects on the mechanical, thermal, and UV-barrier properties as well as their water-resistance are discussed. In general, the polysaccharide–TiO2 hybrid materials showed improved physicochemical properties in a TiO2 content-dependent response. It showed antimicrobial activity against bacteria (gram-negative and gram-positive), yeasts, and molds with enhanced UV-protective effects for food and non-food packaging purposes. The reported applications of functionalized polysaccharide–TiO2 composites include photocatalysts (dye removal from aqueous media and water purification), biomedical (wound-healing material, drug delivery systems, biosensor, and tissue engineering), food preservation (fruits and meat), cosmetics (sunscreen and bleaching tooth treatment), textile (cotton fabric self-cleaning), and dye-sensitized solar cells. Furthermore, the polysaccharide–TiO2 showed high biocompatibility without adverse effects on different cell lines, indicating that their use in food, pharmaceutical, and biomedical applications is safe. However, it is necessary to evaluate the structural changes promoted by the storage conditions (time and temperature) on the physicochemical properties of polysaccharide–TiO2 hybrid composites to guarantee their stability during a determined time.

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Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight disease in bean, produces a toxin known as phaseolotoxin, whose synthesis involves the products of some of the genes found within the Pht region. This region, considered a pathogenicity island, comprises 23 genes arranged in five transcriptional units: two single-gene units (argK, phtL) and three arranged as operons (phtA, phtD, phtM), most with unknown function. In P. syringae pv. phaseolicola, maximal expression of most of the genes encoded in the Pht region and the synthesis of phaseolotoxin require the product of the phtL gene, of unknown function but that has been proposed to have a regulatory role. In order to evaluate the role of phtL gene in P. syringae pv. phaseolicola, we performed a comparative transcriptional analysis with the wild type and a phtL(-) mutant strains using microarrays. The microarray data analysis showed that PhtL regulates the expression not only of genes within the Pht region, but also alters the expression of genomic genes outside it, indicating that this gene has been integrated into the regulatory machinery of the bacterium. The expression changes of many of those genes were confirmed by RT-PCR. This study also demonstrated the importance of the PhtL protein in the process of iron response, and suggests that the effect of PhtL on the expression of pathogenicity related, respiration and oxidative stress genes, observed in this study, appears to be indirect through its influence on the Fur protein expression.

In this work, the ultrasound-assisted extraction (UAE) (operating conditions of sonication amplitude, pulse-cycle, and extraction time) was investigated to obtain an extract rich in biologically active compounds from Annona muricata leaves. In addition, the content of bioactive compounds from the extract by the optimal UAE conditions (UAE extract) was compared with extracts prepared by decoction and infusion. Moreover, Artemia salina toxicity was evaluated in all extracts. UAE extract (using optimal conditions: 80% amplitude, 0.7 s pulse-cycle, for 4.54 min) contained 178.48 mg/100 mL of soluble phenols, 20.18 mg/100 mL of total flavonoids, 27.81 mg/100 mL of hydrolyzable polyphenols, 167.07 mg/100 mL of condensed tannins, 30.44 mg/100 mL of total alkaloids and 14.62 mg/100 mL of total acetogenins. The UAE extract exhibited a high antioxidant capacity and a higher content of bioactive compounds from ~6 to ~927-fold than decoction or infusion, depending on the type of compound. Twenty-four different phenolic compounds were identified in the samples, and UAE extract produced the highest concentration. All extracts were considered non-toxic using the A. salina test. The UAE extract from A. muricata leaves is a rich source of bioactive compounds and can be utilized to formulate therapeutic drugs or nutraceutical foods.

Los hidrolizados proteínicos son una fuente de péptidos bioactivos (PB) y estos compuestos pueden ejercer un papel importante en la salud humana debido a sus diferentes acividades biológicas. El uso de proteasas de origen vegetal es una alternativa potencial para producir PB. El objetivo de este trabajo fue evaluar la capacidad de inhibición de la hemólisis oxidativa (IHO) y actividad antimicrobiana de hidrolizados y fracciones peptídicas obtenidas de la hidrólisis de proteínas de huevo (ovoalbúmina), leche y soya, con proteasas extraídas de frutos de Bromelia pinguin y Bromelia karatas. En general, todos los hidrolizados y fracciones peptídicas presentaron una alta IHO, siendo la fracción peptídica de ≤1 kDa, obtenida de la hidrólisis de ovoalbúmina con proteasas de B. karatas, la que presentó mayor actividad (98.19%). En contraste, ninguno de los hidrolizados registró actividad antimicrobiana, mientras que las fracciones peptídicas (≤5, ≤10 y ≤30 kDa), obtenidas de la hidrólisis de leche con proteasas de B. pinguin, mostraron la mayor actividad antimicrobina (22.26-23.79% de inhibición), contra Listeria innocua. Los resultados resaltan el potencial de las proteasas de B. pinguin y B. karatas para hidrolizar proteínas de diferentes alimentos y generar hidrolizados y PB con alta actividad antioxidante.

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