Preparation and characterization of a novel porous whey protein concentrate/pullulan gel induced by heating for Cu2+ absorption

Xylan derived fluorescence carbon dots composite with cotton cellulose paper as 'turn-off' fluorescence platform for sensitive and selective detection Cu2+ in real samples

The pollution of heavy metals such as Cu2+ is still serious and the discharge of sewage of Cu2+ will cause damage to soil environment and human health. Herein, a biomass-based solid-state fluorescence detection platform (CPU-CDs) was developed as fluorescent sensor for detection Cu2+ via fluorescence and colorimetric dual-model methods in real time. CPU-CDs was composed of xylan-derived CDs (U-CDs) and cotton cellulose paper, which exhibiting good reusability, non-toxicity, excellent fluorescence characteristics and high biocompatibility. Further, CPU-CDs displayed high effectiveness and sensitivity for Cu2+ with the detection limit as low as 0.14 μM, which was well below U.S. EPA safety levels (20 μM). Practical application indicated that CPU-CDs could achieve precision response of Cu2+ change in real environment water samples with good recovery range of 90 %-119 %. This strategy demonstrated a promising biomass solid-state fluorescence sensor for Cu2+ detection for water treatment research, which is of great significance in dealing with water pollution caused by heavy metal ions.

Adsorption of azo dyes by a novel bio-nanocomposite based on whey protein nanofibrils and nano-clay: Equilibrium isotherm and kinetic modeling

Excessive discharge of synthetic azo dyes into the aquatic ecosystem is a global concern. Here, we develop a green approach to remediate dye pollutants by fabricating an easily separable bio-nanocomposite, based on nanofibrils from whey protein concentrate together with montmorillonite. The nanocomposite was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and surface area analysis. Nanofibrils lead to a uniform dispersion of montmorillonite in the matrix and also reinforce the nanocomposite. The adsorption efficacy was monitored using cationic (Chrysoidine-G, Bismarck brown-R), reactive (reactive black-5, reactive orange-16), acidic (acid red-88, acid red-114) and direct (direct violet-51, Congo red) dyes. The nanocomposite adsorbed different dyes with different kinetics, cationic dyes quicker and reactive dyes slower. Greater than 93% of Chrysoidine-G was adsorbed over a wide range of dye concentration and pH. Acidic pH and higher temperature are more favorable for the process. Equilibrium adsorption data were reasonably fitted with a linear (Nernst) isotherm model indicating the existence of an unlimited number of adsorption sites which is consistent with the high experimental uptake of 731 mg/g. Kinetic data were well-described by pseudo-second-order and intra-particle diffusion models. We conclude that this environmentally friendly nanocomposite has good potential for use in wastewater treatment and related purposes.

Interaction of the Exopolysaccharide from Lactobacillus plantarum YW11 with Casein and Bioactivities of the Polymer Complex

There has been an increased application of exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) in fermented dairy products, but interactions between EPS and casein (CAS), and bioactivities of their complex are poorly studied. In this study, EPS produced by Lactobacillus plantarum YW11 (EPS-YW11) was studied for interactions with CAS in a simulated fermentation system acidified by D-(+)-gluconic acid δ-lactone. The results showed that there was interaction between EPS-YW11 and CAS when EPS (up to 1%, w/v) was added to the casein solution (3%, w/v) as observed with increased viscoelasticity, water holding capacity, ζ-potential and particle size of EPS-YW11/CAS complex compared with CAS alone. Microstructural analysis showed that a higher concentration of EPS facilitated more even distribution of CAS particles that were connected through the polysaccharide chains. Infrared spectroscopy further confirmed interactions between EPS and CAS by intermolecular hydrogen bonding, electrostatic and hydrophobic contacts. Further evaluation of the bioactivities of EPS-YW11/CAS complex revealed significantly increased antibiofilm, antioxidation, and bile acids binding capacity. The present study provides further understanding on the mechanism of interactions between EPS produced by LAB and CAS, which would benefit potential applications of EPS in fermented dairy products with enhanced functionality.

Effect of pullulan concentration and pH on the interactions between whey protein concentrate and pullulan during gelation

BACKGROUND

Whey protein concentrate (WPC)/pullulan (PUL) hydrogel is applied as a microencapsulation wall material to protect probiotics. However, the interactions between WPC and PUL during gelation have not been clarified. In the present study, the effects of PUL concentration and pH on the interactions between WPC and PUL during gelation were evaluated with respect to appearance, zeta-potential, sulfhydryl group amount, surface hydrophobicity and infrared spectroscopy measurements. The rheological properties of WPC/PUL gels were also determined.

RESULTS

The results obtained showed that a proper concentration (0.40 g mL^-1 ) of PUL could improve the gel by enhancing the strength of hydrogen bonding, electrostatic interactions and exposure of hydrophobic groups, whereas too much PUL inhibited the formation of disulfide bonds. Furthermore, hydrophobic interactions, disulfide bonds and hydrogen bonds were destroyed in varying degrees under an alkaline environment. The rheological results also demonstrated a similar effect of PUL concentration and pH on the storage modulus (G') of WPC/PUL gels.

CONCLUSION

When the WPC/PUL gel was formed at PUL concentration of 0.40 g mL^-1 and pH 7.0, the interaction between WPC and PUL could be enhanced, which is beneficial for the future application of WPC/PUL gels in the food industry. © 2020 Society of Chemical Industry.