Experimental and in silico approaches for the buffalo whey protein-folic acid complexation elucidation. Molecular changes impacting on protein structure and functionality.

Using a buffalo whey proteins concentrate (BWPC) as a nanocarrier of labile bioactive compounds as vitamins constitutes a very innovative approach with potential application in the food and nutraceutical industries. This work aims to deepen the knowledge of the phenomena occurring in the complexation process of vitamin B9 with BWPC, providing valuable information on the molecular and functional properties of complexes and intervening substances. For such purpose, analytical (SEC-FPLC, Fluorescence spectroscopy, FTIR, DLS, UV-vis spectroscopy) and in-silico methods (molecular docking) were performed to get complementary data. Five types of proteins were identified in the BWPC. Folic acid (FA) interacted with BWPC in buffer pH 7 through H-bonds and hydrophobic interactions, inducing conformational changes and modifying the secondary and tertiary protein structure. The resultant BWPC-FA complexes showed a size distribution in the nanoscale (100-150 nm) with no aggregation. Molecular docking showed that lactoferrin had the highest FA binding affinity. Complexation did not reduce the antioxidant activity of intervening substances. Indeed, the radical scavenging capacity of BWPC-FA was 20 % higher than single BWPC. The obtained results provide relevant data enabling the adding value of the main effluent of buffalo dairy industries.

Molecular interactions involved in the complexation process between buffalo whey proteins concentrate and folic acid.

Using buffalo whey proteins as carrier agents of sensitive molecules raises an interesting approach allowing adding value and minimizing the pollution impact of this by-product. In this context, this work aims to explore the molecular interactions between buffalo whey proteins concentrate (BWPC) and folic acid (FA). For this purpose, fluorescence, UV and FTIR analysis were performed on aqueous or solid dispersions of a buffalo whey protein concentrate (5 µM) (BWPC), with variable concentrations (0-20 µM) of FA. Fluorescence and absorption data were fitted by Stern-Volmer, Beckett, Förster resonance energy transfer, and sphere-of-action models (R2 > 0.9). Derived results suggest that BWPC strongly bind to FA through non-covalent interactions and form ground-state complexes. Additionally, BWPC improves the photostability of FA against UV radiation, and chemical denaturation negatively affects the binding properties. Obtained results encourage further studies of BWPC as carrier agents, which could promote innovative applications for this under-utilized proteins source.

Bio-Packaging Material Impact on Blueberries Quality Attributes under Transport and Marketing Conditions.

Blueberries are highly appreciated for their high antioxidant content but are also particularly susceptible to fungal deterioration. In this work, corn starch and chitosan, byproducts of the fishing industry, as well as active compounds obtained from citrus processing waste were used to obtain active biodegradable film packaging. Blueberries were packed in corn starch-chitosan (CS:CH) films and in active films containing lemon essential oil (LEO) or grapefruit seed extract (GSE). The effects of film packaging on the quality parameters of berries and the fungal incidence of disease during storage were studied and compared to benchmark materials. A conservation assay simulating transport and commercialization conditions was conducted. Blueberries packed in CS:CH films showed antioxidant capacity values closer to those packed in commercial PET containers (Clamshells), preserving 84.8% of the initial antioxidants content. Fruit packed in LEO films exhibited the greatest weight loss and rot incidence, and poor surface color. CS:CH and GSE films controlled the fruit respiration rate and weight loss, therefore they are materials with adequate barrier properties for blueberries conservation. Bags formulated with GSE showed adequate barrier properties to maintain fruit quality attributes without the incidence of rottenness, being an interesting option for blueberries exportation.

Moisture sorption properties and glass transition temperature of a non-conventional exudate gum (Prosopis alba) from northeast Argentine.

Water-solid interactions were explored in purified and freeze-dried Prosopis alba exudate gum as approach to get a deeper insight of structural and functional aspects of this novel biomaterial. Particularly, the study of water-binding properties combined with glass transition temperatures allowed obtaining interesting theoretical data for practical applications. The Guggenheim-Anderson-de Boer (GAB) and Generalized D'Arcy and Watt (GDW) models were applied to describe the sorption behavior and thermodynamic properties of the studied gum. The study of the relationship between relative humidity, water content and thermal transitions allowed to characterize the material in terms of water plasticizing susceptibility as well as define the suitable storage conditions that guarantee the quality, safety and physical stability of P. alba gum. Obtained results contribute to the characterization of a non-conventional exudate gum with great potential for its use in different food industry applications.

Phenolics composition, antioxidant properties and toxicological assessment of Prosopis alba exudate gum.

The objective of this work was to deepen on the study of functional properties of the phytochemicals present in Prosopis alba exudate gum (G), as well as to rule out possible adverse effects of some of its components. Commonly employed purification methods were compared. Filtration prevents further loss of potentially bioactive compounds. The filtrated gum showed a higher concentration of phenolics, flavonoids and tannins than arabic gum, which was correlated with better in vitro antioxidant properties. Particularly, tannins, commonly considered as toxic compounds in exudate gums, were found in lower concentration than in others gums obtained from genus Prosopis and Acacia. The toxicological evaluation performed on rats did not show symptoms of intoxication associated with the administration of the gum. These results provide useful evidence to support the potential use of G as a safe functional food additive with the added benefit of taking advantage of a non-exploited natural resource.

Impact of Prosopis alba exudate gum on sorption properties and physical stability of fish oil alginate beads prepared by ionic gelation.

This study was conducted to evaluate the effect of Prosopis alba exudate gum (G) as encapsulating matrix component on water-solid interactions, physical state, oxidative damage and appearance properties of alginate-chitosan encapsulates containing fish oil. With this purpose, water sorption isotherms were obtained at 25 °C. G increased the hygroscopicity of encapsulates, showing a higher monolayer water content (7.87 ±â€¯0.47% db.) than control (1.07 ±â€¯0.04% db.). G introduction reduced the plasticizing effect of water, increasing the aw range (aw < 0.45) at which samples were in amorphous state and providing the highest protection against lipid oxidation. Appearance properties (chromatic and optical) were affected by hydration and were better maintained in samples containing G at aw > 0.52. These results allow considering Prosopis alba exudate gum, as a novel excipient to protect fish oil encapsulated in low moisture polyelectrolyte systems, with the added benefits of employing an undervalued natural resource.

Prosopis alba exudate gum as novel excipient for fish oil encapsulation in polyelectrolyte bead system.

In this work, a bottom-up approach based on the study of polyelectrolyte interactions was performed in order to evaluate the effect of Prosopis alba exudate gum as novel excipient for fish oil encapsulation in composed calcium-alginate-chitosan beads. Emulsion and beads properties such as oil distribution, encapsulation efficiency, yield, microstructure and thermo-oxidative protection were evaluated. Alginate and gum exert a synergistic effect on emulsion stability properties, which conducted to better oil distribution in the beads and higher encapsulation efficiencies (98%) and yield (89%). The positive effect of including the gum as wall material was observed in terms of a higher oil retention capacity of the alginate beads, improved oxidative thermal stability and better microstructural features. Present results are promising and allowed considering P. alba gum as a novel non-conventional polyelectrolyte for improving Ca-alginate beads microstructure and stability with the added benefit of taking advantage of an available resource currently untapped.

Prosopis alba exudate gum as excipient for improving fish oil stability in alginate-chitosan beads.

The aim of the present work was to employ an exudate gum obtained from a South American wild tree (Prosopis alba), as wall material component to enhance the oxidative stability of fish oil encapsulated in alginate-chitosan beads. For this purpose, beads were vacuum-dried and stored under controlled conditions. Oxidation products, fatty acid profiles and lipid health indices were measured during storage. Alginate-chitosan interactions and the effect of gum were manifested in the FT-IR spectra. The inclusion of the gum in the gelation media allowed decreasing the oxidative damage during storage in comparison to the free oil and alginate-chitosan beads. The gum also improved wall material properties, providing higher oil retention during the drying step and subsequent storage. Fatty acids quality and lipid health indices were widely preserved in beads containing the gum. Present results showed a positive influence of the gum on oil encapsulation and stability, being the main mechanism attributed to a physical barrier effect.

Investigating the photoprotective role of cytochrome b-559 in photosystem II in a mutant with altered ligation of the haem.

Despite many years of study, the physiological role of cytochrome b-559 (Cyt b-559) within the photosystem II (PSII) complex still remains unclear. Here we describe the analysis of a mutant of the green alga Chlamydomonas reinhardtii in which the His ligand to the haem, provided by the alpha subunit, has been replaced by a Cys residue. The mutant is unable to grow photoautotrophically but can assemble oxygen-evolving PSII supercomplexes to 15-20% of the levels found in the wild-type control. Haem is still detected in the isolated PSII supercomplexes but at sub-stoichiometric levels consistent with weaker binding to the mutated cytochrome. Analysis of PSII activity in cells indicates slowed electron transfer in the mutant between plastoquinones QA and QB. We show that PSII activity in the mutant is more sensitive to chronic photoinhibition than the WT control because of two effects: a faster rate of damage and an impaired PSII repair cycle at the level of synthesis and/or incorporation of D1 into PSII. We also demonstrate that Cyt b-559 plays a role during the critical stage of assembling the Mn4CaO5 cluster. Overall we conclude that Cyt b-559 optimises electron transfer on the acceptor side of PSII and plays physiologically important roles in the assembly, repair and maintenance of the complex.