New facile synthesis route for obtaining phase pure LiFePO4/C composite

Carbon-coated, olivine-structured LiFePO4 suitable for cathode material in rechargeable lithium batteries has been prepared via simple, both time and energy low-consuming synthesis route. Procedure involves soaking of cellulose-containing substrate with aqueous precursor solution followed by rapid (several minutes long) single heating step. Cellulose acts as (i) reducing agent and (ii) carbon source which suppresses growth and prevents agglomeration of LiFePO4 particles and also creates a conductive network in LiFePO4/C composite. The crystalline structure, morphology and charge/discharge performance of the as-prepared composite were investigated by means of XRD analysis, electron microscopy and galvanostatic charge-discharge tests. LiFePO4/C powder appears to be nanocrystalline (with mean crystallite size of 37 nm) and electrochemically stable achieving 97% (165 mAhg-1) of its theoretical capacity

Immobilization of alginate-PAC on Sepabeads EC-HA support

Penicillin acylase (PAC) is an important industrial enzyme for the production of many β-lactam antibiotics. It is capable of catalyzing the hydrolysis of penicillin G (Pen G) to generate phenylacetic acid (PAA) and 6-aminopenicillanic acid (6-APA). In this paper, in order to prevent enzyme inactivation, an attempt of coupling enzyme modification and immobilization was presented. Chemical modification was promoted to introduce carbohydrate moiety into the PAC molecule, capable of being covalently linked to an amino support. This seems to provide a possibility to couple the enzyme without risking a reaction at the active site which might cause a loss of activity. PAC molecules were modified by cross-linking with polyaldehyde derivatives of alginate in order to add them new and useful functions. Immobilization of alginate-PAC on Sepabeads EC-HA was used as a model system in order to demonstrate the potential of this strategy. Optimal conditions for covalent immobilization of alginate-PAC from Escherichia coli on support Sepabeads EC-HA, were investigated. The immobilized enzyme was then characterized by evaluating the potential effects of immobilization on its thermal stability, temperature and pH profile in comparison with native non-modified PAC and modified non-immobilized PAC. The maximum amount of the alginate-PAC coupled on the dry support of 99 mg/g was satisfactory. Deactivation rate constants at 50 ºC for free PAC, alginate-PAC and alginate-PAC immobilized on Sepabeads EC-HA were 2,32; 50,65 and 1,68 h-1, respectively. Alginate-PAC and alginate-PAC immobilized on Sepabeads EC-HA had the same pH and temperature optimum as the native non-modified PAC

Antioxidant properties of hydrolysates of wheat gluten as influenced by process conditions

The effects of some relevant process parameters for the Alcalase-catalyzed wheat gluten hydrolysis such as gluten concentration (X1; 1-9% w/v), temperature (X2; 40-60 oC), pH (X3; 7-9) and enzyme/substrate ratio, [E]/[S] ratio (X4; 0.25– 0.75 AU/g of protein) were investigated by the means of an experimental design. The second-order models developed for the degree of hydrolysis, DH, DPPH and ABTS radical scavenging activity of gluten hydrolysates were significant (p<0.01) with a high value of coefficients of determination (0.981-0.992). The statistical analysis showed that each variable had a significant effect on degree of hydrolysis and the antioxidant capacity of both tested systems. Hydrolysis up to around DH = 15% improved DPPH radical scavenging activity, while excessive hydrolysis worsened it. It seemed there was not a correspondence between degree of hydrolysis and ABTS activity at different protein concentrations, suggesting that there were peptides with considerable size presenting a good antioxidant capacity

Peptides with improved antimicrobial activity screened by membrane ultrafiltration from egg white protein hydrolysates

This contribution was aimed at the fractionation and identification of peptides with improved antimicrobial activity from egg white protein hydrolysates, obtained by membrane ultrafiltration. For this purpose, the thermal treated egg white proteins were intensively hydrolysed with a commercial food-grade bacterial endopeptidase from Bacillus licheniformis, namely Alcalase. Thus, obtained hydrolysates were further separated by sequential ultrafiltration into four peptide fractions viz. fraction I (> 30kDa), II (10 - 30 kDa), III (1 - 10 kDa) and IV (< 1kDa) which were investigated in terms of their antimicrobial activity. The antimicrobial activity was tested against Gram-positive bacteria (Staphylococcus aureus ATCC 25923), Gram-negative bacteria (Escherichia coli ATCC 25922) and against yeast Candida albicans (ATCC 24433) by fractions' susceptibility of agar diffusion. Our results showed that these peptide fractions have an intense inhibitory activity on Gram-positive bacteria, poor on Gram-negative bacteria and none inhibitory activity on growth of C. albicans. The results showed interesting antimicrobial potentials versus the tested microorganisms, especially fractions with peptides molecular weight of 10-30 kDa and 1-10 kDa. It can be concluded, that the controlled enzymatic hydrolysis of egg white proteins and their subsequent membrane ultrafiltration is considered to be a suitable way for production of biocative peptides with exhibit antimicrobial efficiency

The synergistic effect of heat treatment on alcalase-assisted hydrolysis of wheat gluten proteins: Functional and antioxidant properties

In order to confirm the gluten potential for inclusion into functional foods, the synergistic effect of the heat treatment and controlled enzymatic hydrolysis on the functional and the antioxidant properties of alcalase-assisted wheat gluten hydrolysates (AWGHs) will be discussed. For this purpose, wheat gluten was heat-treated during 30min at 75 degrees C and intensively hydrolyzed with alcalase at degree of hydrolysis (DH) 16.1%, 22.9%, and 30.2%. All the hydrolysates had excellent solubility over a pH range of 2-12. Emulsifying activity and stability were also improved, while proteolysis was deleterious to foam capacity and stability, water-holding capacity, fat-binding capacity and did not show improvement at higher DH (22.9% and 30.2%). As well, controlled hydrolysis of heat-treated gluten resulted in a remarkable improvement in antioxidant activities. The results show that the heat-treated AWGHs were superior to the untreated hydrolysate in the functional and antioxidant properties tested. Practical applicationsThis report examines existing evidence regarding the wheat gluten proteins (WGP), which is a byproduct from wheat starch processing. It is known that enzymatic hydrolysis is frequently used to improve functional properties of protein hydrolysates and largely dependent on the degree of hydrolysis (DH), which needs to be controlled to elude redundant proteolysis that can deteriorate functionality and cause unfavorable effects. The DH is a substantial factor which affect the hydrolysates' performances and an appropriate selection of protease for WGP hydrolysis will result in maximum biological activity and improved functionalities. Heat treatment is often used to facilitate the proteolysis of proteins. Thus, functional and antioxidant properties of WGP hydrolysates, as a function of heat treatment and the DH were adequately examined in this study and results showed that by combining heat prehydrolysis treatment under controlled conditions, hydrolysates with improved properties can be produced enhancing utilization of WGP in food products

Enzyme encapsulation technologies and their applications in food processing

Applications of enzymes in the food industry have been intensively studied and improved in recent years. Moreover, some food processes without enzymatic reactions are too long or even not possible. Enzyme market is dynamic, not only regarding the economical aspect that is expressed by an annual growth of 7-9 per cent, but also concerning new innovations and studies that have been done in recent years

Controlled enzymatic hydrolysis for improved exploitation of the antioxidant potential of wheat gluten

The aim of the study was to find the optimal operational and process parameters for the enzymatic hydrolysis of wheat gluten in a batch stirred bioreactor regarding both degree of hydrolysis and antioxidant capacity of the obtained hydrolysates. It appeared that impeller geometry and agitation speed influenced the mass transfer resulting in enhanced gluten hydrolysis. The highest initial reaction rate (0.83 0.02 min(-1)) and degree of hydrolysis (30.47%) were achieved with the pitched four-bladed impeller and agitation speed of 350-450 rpm, conditions which provided proper balance between requirements for adequate mass/heat transfer and low shear stress. The impact of other process conditions including gluten concentration, temperature, pH and enzyme gluten (E/S) ratio on the enzymatic reaction was investigated by applying a Box-Behnken experimental design from the viewpoint of the degree of hydrolysis (DH) and antioxidant activity. Three models obtained allowed calculation of the hydrolysis degree, and both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulpfonic acid) radical scavenging activity from a given set of reaction conditions with good predictability. The statistical analysis showed that each variable had a significant effect on degree of hydrolysis and the antioxidant capacity of both tested systems. Hydrolysis up to around DH 15% improved DPPH radical scavenging activity, while excessive hydrolysis worsened it. The ABTS activity of the hydrolysates was not associated with the DPPH activity nor with the DH, revealing that it was not possible to fulfill all desirable quality requirements (maximum degree of hydrolysis and protein yield, maximum DPPH and ABTS scavenging activities) by using the Same reaction conditions. Overall, the study might contribute to approve wheat gluten, a by-product of wheat starch industry, as an accessible and cheap source of bioactive compounds for the development of novel nutraceuticals, cosmetics and drugs

Hydrolysis of egg white and wheat proteins with protease from bacillus licheniformis: fractionation and identification of bioactive peptides

Wheat gluten is a relatively inexpensive industrial byproduct from wheat starch processing, and in Europe also from manufacturing of bioethanol fuel. Egg producers are also faced with problems of excess of egg white because mayonnaise industry and bakery industry use relatively high egg yolk amounts and egg white is the remainder. Of high importance is the production of new value-added products based on gluten and/or egg white proteins with improved properties and specialized functionality to be used in food and biobased consumer products. The objective of this research was a production of both wheat gluten and egg white protein hydrolysates with improved antioxidant properties. For this purpose, both substrates were pretreated by thermal treatment and then intensively hydrolysed with a commercial food-grade bacterial protease, Alcalase. Thus, the obtained hydrolysates were further separated by sequential ultrafiltration into four peptide fraction viz. Fraction I (> 30kDa), II (10 - 30 kDa), III (1 - 10 kDa) and IV (< 1kDa) which were investigated in terms of their antioxidant activity. The antioxidant activity of hydrolysates and peptide fractions were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical scavenging assays and measuring ferric reducing antioxidant power assay. Scavenging of 2,2′- diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) by Fraction III, prepared with gluten protein was found to be significantly higher than other gluten or egg white fractions. The results show that the fractionated hydrolysates were superior to the original hydrolysate in the antioxidative activity tested in all cases and can be concluded that by combining thermal pretreatment and controlled enzymatic hydrolysis, the hydrolysates with improved antioxidant properties can be produced enhancing utilization of egg white and gluten in food products