Spent Yeast Waste Streams as a Sustainable Source of Bioactive Peptides for Skin Applications.

Spent yeast waste streams are a byproduct obtained from fermentation process and have been shown to be a rich secondary source of bioactive compounds such as phenolic compounds and peptides. The latter are of particular interest for skin care and cosmetics as they have been shown to be safe and hypoallergenic while simultaneously being able to exert various effects upon the epidermis modulating immune response and targeting skin metabolites, such as collagen production. As the potential of spent yeast's peptides has been mainly explored for food-related applications, this work sought to understand if peptide fractions previously extracted from fermentation engineered spent yeast (Saccharomyces cerevisiae) waste streams possess biological potential for skin-related applications. To that end, cytotoxic effects on HaCat and HDFa cells and whether they were capable of exerting a positive effect upon the production of skin metabolites relevant for skin health, such as collagen, hyaluronic acid, fibronectin and elastin, were evaluated. The results showed that the peptide fractions assayed were not cytotoxic up to the highest concentration tested (500 µg/mL) for both cell lines tested. Furthermore, all peptide fractions showed a capacity to modulate the various target metabolites production with an overall positive effect being observed for the four fractions over the six selected targets (pro-collagen IαI, hyaluronic acid, fibronectin, cytokeratin-14, elastin, and aquaporin-9). Concerning the evaluated fractions, the overall best performance (Gpep > 1 kDa) was of an average promotion of 41.25% over the six metabolites and two cell lines assessed at a concentration of 100 µg/mL. These results showed that the peptide fractions assayed in this work have potential for future applications in skin-related products at relatively low concentrations, thus providing an alternative solution for one of the fermentation industry's waste streams and creating a novel and highly valuable bioactive ingredient with encompassing activity to be applied in future skin care formulations.

ß-lactoglobulin micro- and nanostructures as bioactive compounds vehicle: In vitro studies.

ß-Lactoglobulin (ß-Lg) is known to be capable to bind hydrophilic and hydrophobic bioactive compounds. This research aimed to assess the in vitro performance of ß-Lg micro- (diameter ranging from 200 to 300 nm) and nano (diameter < 100 nm) structures associated to hydrophilic and hydrophobic model compounds on Caco-2 cells and under simulated gastrointestinal (GI) conditions. Riboflavin and quercetin were studied as hydrophilic and hydrophobic model compounds, respectively. Cytotoxicity experiment was conducted using in vitro cellular model based on human colon carcinoma Caco-2 cells. Moreover, the digestion process was simulated using the harmonized INFOGEST in vitro digestion model, where samples were taken at each phase of digestion process - oral, gastric and intestinal - and characterized in terms of particle size, polydispersity index (PDI), surface charge by dynamic light scattering (DLS); protein hydrolysis degree by 2,4,6-trinitrobenzene sulfonic acid (TNBSA) assay and native polyacrylamide gel electrophoresis; and bioactive compound concentration. Caco-2 cell viability was not affected up to 21 × 10-3 mg mL-1 of riboflavin and 16 × 10-3 mg mL-1 quercetin on ß-Lg micro- and nanostructures. In the oral phase, ß-Lg structures' particle size, PDI and surface charge values were not changed comparing to the initial ß-Lg structures (i.e., before being subjected to in vitro GI digestion). During gastric digestion, ß-Lg structures were resistant to proteolytic enzymes and to acid environment of the stomach - confirmed by TNBSA and native gel electrophoresis. In vitro digestion results indicated that ß-Lg micro- and nanostructures protected both hydrophilic and hydrophobic compounds from gastric conditions and deliver them to target site (i.e., intestinal phase). In addition, ß-Lg structures were capable to enhance riboflavin and quercetin bioaccessibility and bioavailability potential compared to bioactive compounds in their free form. This study indicated that ß-Lg micro- and nanostructures were capable to enhance hydrophilic and hydrophobic compounds bioavailability potential and they can be used as oral delivery systems.

Development of iron-rich whey protein hydrogels following application of ohmic heating - Effects of moderate electric fields.

The influence that ohmic heating technology and its associated moderate electric fields (MEF) have upon production of whey protein isolate cold-set gels mediated by iron addition was investigated. Results have shown that combining heating treatments (90°C, 5min) with different MEF intensities let hydrogels with distinctive micro and macro properties - i.e. particle size distribution, physical stability, rheological behavior and microstructure. Resulting hydrogels were characterized (at nano-scale) by an intensity-weighted mean particle diameter of 145nm, a volume mean of 240nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3V∙cm-1 was combined with a cold gelation step using 33mmol∙L-1 of Fe2+. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10V∙cm-1. According to transmission electron microscopy, ohmic heating gave rise to a more homogenous and compact fine-stranded whey protein-iron microstructure. Ohmic heating appears to be a promising technique, suitable to tailor properties of whey protein gels and with potential for development of innovative functional foods.