Dilek Ercili-Cura

One-step method for isolation and purification of native β-lactoglobulin from bovine whey.

BACKGROUND The major whey protein β-lactoglobulin (BLG) has been widely studied for its functional properties. The aim of this study was to develop an efficient, inexpensive and rapid one-step method for the isolation and purification of BLG while preserving its native structure. RESULTS BLG was purified from defatted whey obtained from raw cows milk by anion exchange chromatography. Protein purity and identity were determined using reverse phase high-performance liquid chromatography and mass spectrometry. Total BLG yield was 80% with protein purity from 97 to 99%. BLG isoforms A and B were separated into fractions of 91 and 99% purity respectively. The structure and native conformation of the isolated BLG were compared with those of standard commercial BLG by circular dichroism spectrometry, susceptibility to various crosslinking enzymes and enzyme-linked immunosorbent assay inhibition. CONCLUSION The proposed method is very useful for the rapid preparation of BLG suitable for studying antigenic and molecular characteristics of this protein, as well as the effect of food processing on these properties. The procedure requires only 1 day for the purification of about 300 mg of BLG from a single run using a small column (2.5 cm × 20 cm) of diethylaminoethyl Sephadex and has potential for scaling up.

Directing enzymatic cross-linking activity to the air–water interface by a fusion protein approach

Enzymatic cross-linking of proteins is of great interest due to an effective and controlled way of modifying the structures of protein networks. Enzyme-aided structural engineering aims at enhanced stabilisation of foams, emulsions and dispersions by enzymatically inducing intra- and intermolecular cross-links between proteins in continuous phase and/or at interfaces. Formation of stronger interfacial structures protects air bubbles or oil droplets against coalescence, and in some applications, may even be preferable to bulk reactions. In this work we studied direction of enzymatic cross-linking reactions to the air–water interface by enhancing the functionality of enzymes as fusion proteins. We used a hydrophobin–laccase fusion protein, HFBI–MaL, where the surface active hydrophobin component facilitates the access for laccase to cross-link β-casein film directly at the air–water interface. As a result, enhanced cross-linking was shown by means of surface dilatational rheology, where increased G moduli indicated formation of a stronger film with the fusion protein compared to native laccase.

Impact of Total Solid Content and Extraction pH on Enzyme-Aided Recovery of Protein from Defatted Rapeseed (Brassica rapa L.) Press Cake and Physicochemical Properties of the Protein Fractions

Pectinase treatment was used to facilitate protein recovery from defatted rapeseed (Brassica rapa) cold-pressing residue in water-lean conditions and without pH adjustment. Effect of extraction pH on protein yield and physiochemical properties of the protein concentrates was assessed. Enzymatic hydrolysis of carbohydrates was feasible at high (40%) solid content and improved protein recovery at pH 6. Comparable protein yields (40-41% of total protein) from enzyme-aided water extraction (pH 6) and nonenzymatic alkaline extraction (pH10) at 10% solid content suggested that after enzymatic treatment, rapeseed protein could be extracted without exposure to alkali. However, water extraction required dilute conditions, whereas alkaline extraction was feasible also at 20% solid content. The water extracts possessed better protein solubility, higher ζ-potential, and smaller particle size than isoelectric precipitates from alkaline extraction, indicating higher dispersion stability. This is suggested to be mediated by electrostatic interactions between proteins and pectic carbohydrates in the water extracts.

Structuring colloidal oat and faba bean protein particles via enzymatic modification

Oat and faba bean protein isolates were treated with transglutaminase from Streptomyces mobaraensis and tyrosinase from Trichoderma reesei to modify the colloidal properties of protein particles in order to improve their colloidal stability and foaming properties. Transglutaminase crosslinked faba bean protein extensively already with 10nkat/g enzyme dosage. Oat protein was crosslinked to some extent with transglutaminase with higher dosages (100 and 1000nkat/g). Transglutaminase increased the absolute zeta-potential values and reduced the particle size of oat protein particles. As a result, the colloidal stability and foaming properties were improved. Tyrosinase had limited crosslinking ability on both plant protein materials. Tyrosinase greatly reduced the solubility of oat protein despite limited crosslinking. Tyrosinase did not have effect on zeta-potential or colloidal stability of either protein, but it impaired foaming properties of both. Thus, the crosslinking enzymes studied caused significantly different end product functionality, presumably due to the different mechanism of action.

Protein From Oat: Structure, Processes, Functionality, and Nutrition

Abstract Oat is a robust high-protein cereal that grows well in northern regions. Unlike Triticeae cereals, the major storage protein is a globulin, which is higher in essential amino acids than prolamin storage proteins. Oat protein can be tolerated by most celiac individuals, making it an interesting raw material for the ever-expanding gluten-free market. Although well-suited in bakery products, the applicability of oat protein is still limited in liquid and semisolid foods because of its low solubility at neutral and mildly acidic conditions. Enzymatic modifications have shown promising results, and could be utilized for the expansion of applications in the future. The recent developments in new sustainable technologies for oat fractionation have enabled production of oat protein ingredients with better functionalities.Oat is a robust high-protein cereal that grows well in northern regions. Unlike Triticeae cereals, the major storage protein is a globulin, which is higher in essential amino acids than prolamin storage proteins. Oat protein can be tolerated by most celiac individuals, making it an interesting raw material for the ever-expanding gluten-free market. Although well-suited in bakery products, the applicability of oat protein is still limited in liquid and semisolid foods because of its low solubility at neutral and mildly acidic conditions. Enzymatic modifications have shown promising results, and could be utilized for the expansion of applications in the future. The recent developments in new sustainable technologies for oat fractionation have enabled production of oat protein ingredients with better functionalities.