Enzymatic modification and adsorption of hydrophobic zein proteins on lactic acid bacteria stabilize Pickering emulsions.

The effect of enzymatic and physical modifications of the surface of two different strains from lactic acid bacteria, Lactobacillus rhamnosus (LGG) and Lactobacillus delbruekii subs. lactis ATCC 4797 (LBD), to stabilize medium-chain triglyceride (MCT) oil based Pickering emulsions were investigated. A section of cell wall degrading enzymes, lysozyme from chicken egg white and human, lysostaphin, mutanolysin from Streptomyces globisporus and proteinase k and the hydrophobic protein zein were used for enzymatic and physical surface modifications. Cell surface modifications were characterized by optical microscopy, scanning electron cryo-microscopy (Cryo-SEM), transmission electron microscopy (TEM), microbial adhesion to hexadecane (MATH) test and zeta potential measurements. The modified cell hydrophobicity in terms of MATH values were increased (around four times) by the enzymatic and physical modifications for LBD and LGG compared to the control. Emulsions stabilized by modified bacterial cells showed higher stability in comparison with unmodified samples, especially for the samples modified with chicken egg lysozyme. Confocal microscopy revealed that the modified bacterial cells were absorbed at the interface between oil and water and preventing the oil particles from coalescence. Thus, modified bacterial cells can be used to formulate food-grade stable Pickering emulsions. Such Pickering emulsions can potentially be clean label alternatives to replace the conventional emulsion preparations.

Multi-species colloidosomes by surface-modified lactic acid bacteria with enhanced aggregation properties.

HYPOTHESIS: Surface modification of lactic acid bacteria enhances their adsorption and aggregation at air-water interface and enables stabilization of microbubbles that spontaneously transform into water-filled colloidosomes, which can be further modified using LBL formulations. EXPERIMENTS: The bacterial physicochemical properties were characterized using water contact angle (WCA) measurement, bacterial aggregation assay and zeta potential measurement. Cell viability was enumerated using plate-counting method. The LBL reinforcement of colloidosomes was examined by zeta potential measurement and the formed microstructure was investigated using bright-field microscopy, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Shell permeability of colloidosomes was evaluated using a dye release study. FINDINGS: Bacteria surface-modified using octenyl succinic anhydride (OSA) expressed strong adsorption and aggregation at air-water interface when producing microbubbles. Bacteria with enhanced aggregation ability formed stable shells, enabling complete removal of air and air-water interface without shell disintegration. The formed colloidosomes were studied as they were, or were further reinforced by LBL deposition using polymer or hybrid formulations. Hybrid coating involved assembly of two bacterial species producing colloidosomes with low shell porosity. The findings can be exploited to organize different living bacteria into structured materials and to encapsulate and release substances of diverse sizes and surface properties.

Efficient chemical hydrophobization of lactic acid bacteria - One-step formation of double emulsion.

A novel concept of stabilizing multiple-phase food structure such as emulsion using solely the constitutional bacteria enables an all-natural food grade formulation and thus a clean label declaration. In this paper, we propose an efficient approach to hydrophobically modifying the surface of lactic acid bacteria Lactobacillus rhamnosus (LGG) using lauroyl ahloride (LC) in non-aqueous media. Compared to the unmodified bacteria, cell hydrophobicity was dramatically altered upon modification, according to the higher percentages of microbial adhesion to hexadecane (MATH) and water contact angles (WCA) of LC-modified bacteria. No evident changes were found in bacterial surface charge before and after LC modification. By using one-step homogenization, all the modified bacteria were able to generate stabile water-in-oil-in-water (W/O/W) double emulsions where bacteria were observed on oil-water interfaces of the primary and secondary droplets. Modification using high LC concentrations (10 and 20 w/w%) led to rapid autoaggregation of bacteria in aqueous solution. A long-term lethal effect of modification primarily came from lyophilization and no apparent impact was detected on the instantaneous culturability of modified bacteria.

Effects of high hydrostatic pressure on the rheological properties and foams/emulsions stability of Alyssum homolocarpum seed gum.

The ability to modify food and increase the shelf life by enhanced stability using nonthermal process is of interest to many food companies. Here, we investigate the effects of high hydrostatic pressure (HHP), as a nonthermal process, at various pressure levels (200, 400, and 600 MPa for 30 min) on the functional properties of aqueous dispersions of Alyssum homolocarpum seed gum (AHSG). In this regard, the rheological properties, foam stability, and emulsion stability of the HHP-treated gums were analyzed and compared. Dynamic oscillatory test indicated that the HHP-treated gums had more gel-like behavior than viscous-like behavior (storage modulus > loss modulus) at designated pressures. When AHSG was treated by HHP, both elastic (G') and viscous (G″) moduli were increased compared to the native AHSG. The native- and HHP-treated gums exhibited a shear-thinning (pseudoplastic) behavior. Furthermore, the pressure levels have a significant effect on consistency coefficient, flow behavior index, and yield stress (p < .05) of AHSG. The results showed that the HHP-treated gums lead to improve the foam and emulsion stability of AHSG. Finally, we assume that HHP-treated AHSG improves texture in the food materials.

The dependency of rheological properties of Plantago lanceolata seed mucilage as a novel source of hydrocolloid on mono- and di-valent salts.

The effects of NaCl and CaCl2 (0-200 mM) on the rheological properties of Plantago lanceolata seed mucilage (PLSM) as a novel potential source of polysaccharide gum were investigated in this study. Furthermore, FTIR analysis was measured to supply more structural information. The FTIR spectra revealed that PLSM with the presence of glycoside bonds and carboxyl and hydroxyl groups behave like a typical polyelectrolyte. It was observed that the gum solutions exhibited viscoelastic properties under the given conditions and the addition of salts had significant affection on the rheological parameters of gum solutions. The weak gel-like behavior (0.1 < tan Î´ < 1) observed for all solutions at different ion types and ionic strengths. The limiting values of strain mostly increased with enhance cation concentration due to the intermolecular interaction and therefore increase the stiffness of gum solutions in the concentrated domain. The frequency sweep results showed that developing ion concentration had a positive effect on the viscoelasticity of gum solutions which Ca2+ was more effective than Na+. Tanglertpaibul&Rao model showed the highest efficiency to evaluate the intrinsic viscosity of PLSM for all co-solutes. The results of this study could be useful when considering the effects of salts on food systems.

Enhanced Transepithelial Permeation of Gallic Acid and (-)-Epigallocatechin Gallate across Human Intestinal Caco-2 Cells Using Electrospun Xanthan Nanofibers.

Electrospun xanthan polysaccharide nanofibers (X) were developed as an encapsulation and delivery system of the poorly absorbed polyphenol compounds, gallic acid (GA) and (-)-epigallocatechin gallate (EGCG). Scanning electron microscopy was used to characterize the electrospun nanofibers, and controlled release studies were performed at pH 6.5 and 7.4 in saline buffer, suggesting that the release of polyphenols from xanthan nanofibers follows a non-Fickian mechanism. Furthermore, the X-GA and X-EGCG nanofibers were incubated with Caco-2 cells, and the cell viability, transepithelial transport, and permeability properties across cell monolayers were investigated. An increase of GA and EGCG permeability was observed when the polyphenols were loaded into xanthan nanofibers, compared to the free compounds. The observed in vitro permeability enhancement of GA and EGCG was induced by the presence of the polysaccharide nanofibers, which successfully inhibited efflux transporters, as well as by tight junctions opening.

In vitro permeability enhancement of curcumin across Caco-2 cells monolayers using electrospun xanthan-chitosan nanofibers.

Xanthan-Chitosan (X-Ch) polysaccharides nanofibers were prepared using electrospinning processing as an encapsulation and delivery system of curcumin (Cu). The X-Ch-Cu nanofibers remained stable in aqueous HBSS medium at pH 6.5 and pH 7.4, mainly due to the ability of oppositely charged xanthan-chitosan polyelectrolytes to form ionically associated electrospun nanofibers. The xanthan-chitosan-curcumin nanofibers were incubated with Caco-2 cells, and the cell viability, transepithelial transport and permeability properties across cell monolayers were investigated. After 24 h of incubation, the exposure of Caco-2 cell monolayers to X-Ch-Cu nanofibers resulted in a cell viability of ∼80%. A 3.4-fold increase of curcumin permeability was observed when the polyphenol was loaded into X-Ch nanofibers, compared to the free curcumin. This increased in vitro transepithelial permeation of curcumin without compromising cellular viability was induced by interactions upon contact between the nanofibers and the Caco-2 cells, leading to the opening of the tight junctions. The results obtained revealed that X-Ch nanofibers can be used for oral delivery applications of poorly water-soluble compounds at the gastrointestinal tract.

Electrospun Phospholipid Fibers as Micro-Encapsulation and Antioxidant Matrices.

Electrospun phospholipid (asolectin) microfibers were investigated as antioxidants and encapsulation matrices for curcumin and vanillin. These phospholipid microfibers exhibited antioxidant properties which increased after the encapsulation of both curcumin and vanillin. The total antioxidant capacity (TAC) and the total phenolic content (TPC) of curcumin/phospholipid and vanillin/phospholipid microfibers remained stable over time at different temperatures (refrigerated, ambient) and pressures (vacuum, ambient). ¹H-NMR confirmed the chemical stability of both encapsulated curcumin and vanillin within phospholipid fibers. Release studies in aqueous media revealed that the phenolic bioactives were released mainly due to swelling of the phospholipid fiber matrix over time. The above studies confirm the efficacy of electrospun phospholipid microfibers as encapsulation and antioxidant systems.