Transglutaminase-mediated macromolecular assembly: production of conjugates for food and pharmaceutical applications.

Various strategies have been explored in the last 20 years to modify the functional properties of proteins and, among these, protein/polymer conjugation resulted one of the most successful approaches. Thus, the surface modification of polypeptides of potential industrial interest by covalent attachment of different macromolecules is nowadays regarded as an extremely valuable technique to manipulate protein activities. Protein derivatives with a number of either natural or synthetic polymers, like different polysaccharides or polyethylene glycol, have been obtained by both chemical and enzymatic treatments, and in this context, the crosslinking enzyme transglutaminase is attracting an increasing attention as a simple and safe means for protein processing in vitro. In this short review, we summarized the most significant experimental findings demonstrating that a microbial form of the enzyme is an effective tool to obtain several biopolymer-based conjugates potentially useful for both food and pharmaceutical applications.

Swelling, mechanical, and barrier properties of albedo-based films prepared in the presence of phaseolin cross-linked or not by transglutaminase.

Edible films were obtained from Citrus paradisi grapefruit albedo homogenates and bean protein phaseolin modified or not by the enzyme transglutaminase. Swelling capability, barrier performance to water vapor, oxygen and carbon dioxide, and mechanical properties of such films were investigated. The addition of the protein, mostly in the presence of transglutaminase, provide films less swellable at pH values above 5 compared to films made by albedo homogenates only, whereas the action of the enzyme clearly improves mechanical properties producing more stretchable and elastic films. Moreover, transglutaminase-mediated cross-linking of phaseolin gives rise to films less permeable to carbon dioxide and able to offer a high barrier to water vapor. These findings suggest that albedo-phaseolin film prepared in the presence of transglutaminase can be a promising candidate to be used as food edible wrap.

Impact of dehulling on the physico-chemical properties and in vitro protein digestion of common beans (Phaseolus vulgaris L.).

The objective of this study was to understand the effect of dehulling on the microstructural, physico-chemical characteristics, and in vitro protein digestion of common bean flours with particular regard to differences between adults and infants. The microstructure of flour samples from undehulled (WB) and manually dehulled (SB) beans, observed through scanning electron microscopy, showed that WB starch granules appeared to be surrounded by an integral matrix, while the SB starch granule structure was still visible although covered by protein clusters. The starch granules were oval and spherical, with heterogeneous sizes ranging from 19 to 30 µm in diameter. Particle size analysis determined with a laser diffraction particle size analyzer showed similar bimodal particle size distributions of small (1-25 µm) and large (>100 µm) granules, though the particle size of WB was obviously higher than SB. Color and other physico-chemical analyses showed that dehulling had significant (P < 0.05) influence on all investigated characteristics. The in vitro gastric and duodenal digestion experiments carried out under physiological conditions showed that the SB samples are more likely to be digested by infants. From our results, it is possible to conclude that the dehulling process improves bean flour protein digestion which could be utilized in various food applications.

Fennel waste-based films suitable for protecting cultivations.

Biodegradable, flexible, and moisture-resistant films were obtained by recycling fennel waste and adding to fennel homogenates the bean protein phaseolin that was modified or not modified by the enzyme transglutaminase. All films were analyzed for their morphology, mechanical properties, water vapor permeability, and susceptibility to biodegradation under soil-like conditions. Our experiments showed that transglutaminase treatment of the phaseolin-containing fennel waste homogenates allowed us to obtain films comparable in their mechanical properties and water vapor permeability to the commercial films Ecoflex and Mater-Bi. Furthermore, biodegradability tests demonstrated that the presence of the enzyme in the film-casting sample significantly influences the integrity of such a product that lasts longer than films obtained either with fennel waste alone or with a mixture of fennel waste and phaseolin. These findings indicate the fennel-phaseolin film prepared in the presence of transglutaminase to be a promising candidate for a new environmentally friendly mulching bioplastic.