Application of electric fields to clean ultrafiltration membranes fouled with whey model solutions

Enhanced membrane fouling control and trace organic compounds removal during microfiltration by coupling coagulation and adsorption in an electric field

Coupling electric field, coagulation, and powdered activated carbon (PAC) adsorption in the microfiltration (MF) process was an effective strategy for membrane fouling alleviation and trace organic compounds (TrOCs) elimination. In the electric field, the surface charges of bovine serum albumin (BSA) molecules and kaolin particles distributed along the direction of the electric field and formed electric dipoles, which lowered electrostatic repulsion between BSA-BSA, BSA-kaolin, and kaolin-kaolin, resulting in enhanced particle aggregation and turbidity reduction. Electrophoretic migration also strengthened the interaction between particles and polyaluminum chloride (PACl). Protein removal showed a significant linear correlation with the transmembrane pressure (TMP), and the slope variation of the fitting curves reflected the role of the electric field in the BSA removal and membrane fouling control. Under the synergistic function of electric field, coagulation, and PAC adsorption, the MF system achieved an 80.7% reduction on membrane fouling, an average BSA removal of 76.4%, and TrOCs elimination of 65.3%-81.7%. Electrochemical oxidation was the main contributor to the TrOCs removal when 2.5 V voltage was applied, and could also prolong the service life of PAC.

The effect of composite enzyme catalysis whey protein cross-linking on filtration performance

In this study, enzymatic cross-linked whey protein coupling ultrafiltration was used to reduce membrane fouling and increase whey protein recovery rate. The filtration efficiency and protein interaction with the membrane surface were investigated. The results showed that the protein recovery rate and relative flux of transglutaminase catalysis protein followed by tyrosinase each increased by approximately 30% during ultrafiltration. The total membrane resistance was reduced by approximately 20%. The shape of the transglutaminase and tyrosinase cross-linked protein had somewhat spherical and cylindrical structure similar to an elongated shape based on fluorescence microscopy imaging, which indicated membrane resistance reduction. Fluorescence excitation-emission matrix spectroscopy (EEM) showed that the permeation peak intensities of transglutaminase followed by tyrosinase catalysis protein decreased sharply in the tryptophan and aromatic-like protein fields, indicating that most protein was rejected after ultrafiltration. The repulsive interaction energy was increased between the cross-linked proteins and membrane based on extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis.

Membrane Fractionation of Protein Hydrolysates from By-Products: Recovery of Valuable Compounds from Spent Yeasts

Spent brewer’s yeast (Saccharomyces sp.), the second most generated by-product from the brewing industry, contains bioactive and nutritional compounds with high added value such as proteins (40–50%), polysaccharides, fibers and vitamins. Molecules of interest from agro-industrial by-products need to be extracted, separated, concentrated, and/or purified so that a minimum purity level is achieved, allowing its application. Enzymatic hydrolysis has been successfully used in the production of peptides and protein hydrolysates. The obtained hydrolysates require efficient downstream processes such as membrane technology, which is an important tool for the recovery of thermolabile and sensitive compounds from complex mixtures, with low energy consumption and high specificity. The integration of membrane techniques that promote the separation through sieving and charge-based mechanisms is of great interest to improve the purity of the recovered fractions. This review is specifically addressed to the application of membrane technologies for the recovery of peptides from yeast protein hydrolysates. Fundamental concepts and practical aspects relative to the ultrafiltration of agro-industrial protein hydrolysates will be described. Challenges and perspectives involving the recovery of peptides from yeast protein hydrolysates will be presented and thoroughly discussed.

Recovery of high-concentration volatile fatty acids from wastewater using an acidogenesis-electrodialysis integrated system

Recovery of volatile fatty acids (VFAs) from wastewater is an important route for wastewater valorization. Selective acidogenic fermentation enables an efficient production of VFAs from wastewater, whereas electrodialysis (ED) provides an effective approach to concentrate VFAs. However, these two processes have not been coupled in one single system previously. In this study, an acidogenesis-ED integrated system that coupled a continuous acidogenesis with a batch process of VFA concentration was developed for recovery of high-concentration VFAs from wastewater. Under 20.0 V voltage, the acetate was concentrated by 4-fold and the propionate and butyrate were concentrated by over 3-fold in the integrated system after 528-h operation. The declined VFAs recovery ratios at the later stage due to significant reverse diffusion indicate a need to prevent product over-accumulation. This work demonstrated the feasibility of the acidogenesis-ED integrated reactor for wastewater valorization and discussed the remaining challenges and opportunities.