Susceptibility of Vegetative Cells and Endospores of Bacillus cereus to Rhamnolipid Biosurfactants and Their Potential Application in Dairy.

Bacillus cereus is a Gram-positive, endospore-forming bacterium well-known as a food pathogen that causes great losses in the food industry, especially in dairy. In this study, rhamnolipid (RL) biosurfactants were evaluated as a bio-based alternative for controlling the growth of vegetative cells and endospores of B. cereus. RLs were tested against 14 B. cereus strains isolated from different types of foodstuffs. The antimicrobial activity against vegetative cells and endospores revealed minimal inhibitory concentration (MIC) values of 0.098 mg/mL for almost all strains tested and minimal bactericidal concentration (MBC) varying between 0.098 and >25 mg/mL. The presence of RLs inhibited endospore germination by more than 99%, reducing by 5.5 log the outgrowth of strain 0426. Scanning and transmission electron microscopy confirmed that exposure to RL causes damage to the structure of endospores. When skim milk was utilized as a food model, RL inhibited the growth of vegetative cells and endospores of B. cereus, showing MBC of 3.13 mg/mL for the vegetative cells of strain 0426. The surfactant also reduced bacterial growth in milk at refrigerator temperature. The results suggest that RLs are promising candidates for the development of novel strategies to control B. cereus in the food industry.

Microbial surfactants in nanotechnology: recent trends and applications.

The interest in nano-sized materials to develop novel products has increased exponentially in the last decade, together with the search for green methods for their synthesis. An alternative to contribute to a more sustainable approach is the use of microbial-derived molecules to assist nanomaterial synthesis. In this sense, biosurfactants (BSs) have emerged as eco-friendly substitutes in nano-sized materials preparation. The inherent amphiphilic and self-assembly character of BSs associated with their low eco-toxicity, biodegradability, biocompatibility, structural diversity, biological activity, and production from renewable resources are potential advantages over chemically-derived surfactants. In nanotechnology, these versatile molecules play multiple roles. In nanoparticle (NP) synthesis, they act as capping and reducing agents and they also provide self-assembly structures to encapsulation, functionalization, or templates and act as emulsifiers in nanoemulsions. Moreover, BSs can also play as active compounds owing to their intrinsic biological properties. This review presents the recent trends in the development of BS-based nanostructures and their biomedical and environmental applications. Fundamental aspects regarding their antimicrobial and anticancer activities are also discussed.

Development of collagen/nanohydroxyapatite scaffolds containing plant extract intended for bone regeneration.

In this study scaffolds of nanohydroxyapatite (nHA) and anionic collagen (C) combined with plant extracts intended for bone tissue repair were developed. Grape seed (P), pomegranate peel (R) and jabuticaba peel (J) extracts were used as collagen crosslinker agents in order to improve the materials properties. All crude extracts were effective against Staphylococcus aureus, but only for CR scaffold inhibition zone was noticed. The extracts acted as crosslinking agents, increasing enzymatic resistance and thermal stability of collagen. The extracts showed cytotoxicity at the concentrations tested, while nHA increased cell viability. The scaffolds presented porosity and pore size appropriate for bone growth. CR, CnHAP, CnHAR and CnHAJ increased the cell viability after 24 h. The combination of collagen, nHA and plant extracts offers a promising strategy to design novel biomaterials for bone tissue regeneration.

Chitosan and gelatin materials incorporated with phenolic extracts of grape seed and jabuticaba peel: Rheological, physicochemical, antioxidant, antimicrobial and barrier properties.

In this study, chitosan and gelatin materials incorporated with grape seed (Vitis vinifera L.) (VSE) and jabuticaba peel (Plinia cauliflora) (PPE) extracts were developed with potential application as food coatings. It was evaluated how the concentration of the extracts and their addition order in the polymeric matrix affect its properties. Samples with VSE presented a higher total phenolic content and also a more elastic behavior than samples with PPE. The addition order effect over viscosity was the opposite for the extracts, and for the samples with VSE a lower viscosity was obtained when the extract was added before gelatin. All samples were hydrophilic, a good result for application as coatings. Films with PPE were less soluble than chitosan/gelatin film, and CG5P sample was chosen as the most suitable for the desired application, due to its lower water vapor permeation value. The microbial permeation test showed that all samples avoid microorganism growth, extending shelf life of food. The results of this study revealed the extracts concentration was the main factor which influenced the studied parameters; however, their addition order had significant importance on rheological and barrier properties, the ones most influenced by the availability of extract compounds in the polymeric system.