Addressing challenges in the ultrafiltration of biomolecules from complex aqueous environments

An innovative exploration to identify and isolate the dominant-flocculated-species from polytitanium chloride synthesized by electrodialysis

Abundance of dominant-flocculated-species is the key to determine coagulation performance of coagulant. Titanium-based coagulants have garnered considerable attention due to their high coagulation efficiency, but with a current challenge of the identification and isolation of the dominant-flocculated-species. Herein, polytitanium chloride (PTC), enriched with dominant-flocculated-species, was successfully synthesized by electrodialysis through accurate micro-interface control of the reaction among Ti-hydrolyzed-species and OH-. Special attention was paid to a feasible and high-effective strategy to isolate the dominant-flocculated-species from PTC through one-step rapid ultrafiltration. Selective preference was the ultrafiltration membranes (made of polyethersulfone) with a molecular weight cut-off of 5 kDa, which enabled the isolation of the dominant-flocculated-species, named PTC-5k. Results from the electrospray time-of-flight mass spectrometry (ESI-TOF-MS) proved a large proportion of the small and medium-sized hydrolyzed products as dominant-flocculated-species in PTC-5k, with the main signals concentrated between m/z 100 and 500. This composition achieved approximately 15.0% higher removal of organic matter with a 33.0% reduction in dosage compared to PTC. Unique snowflake-like branched structure of PTC-5k enhanced the coagulation mechanisms of sweeping and adsorption-bridging flocculation. Worth noting was the more compact flocs formed by PTC-5k than PTC, which was the probable reason for the mitigated fouling of ceramic membrane when PTC-5k was utilized as pre-treatment methodology. Continuous operation of ceramic membrane filtration up to 30 h, demonstrated 30% improvement in stable flux compared to PTC. This study provides the strategy for the isolation of Ti-dominant-flocculated-species, and lays the foundation for practical application.

Two-dimensional chromatography in screening of bioactive components from natural products

INTRODUCTION

Screening and analysis of bioactive components from natural products is a fundamental part of new drug development and innovation. Two-dimensional (2D) chromatography has been demonstrated to be an effective method for screening and preparation of specific bioactive components from complex natural products.

OBJECTIVE

To collect details of application of 2D chromatography in screening of natural product bioactive components and to outline the research progress of different separation mechanisms and strategies.

METHODOLOGY

Three screening strategies based on 2D chromatography are reviewed, including traditional separation-based screening, bioactivity-guided screening and affinity chromatography-based screening. Meanwhile, in order to cover these aspects, selections of different separation mechanisms and modes are also presented.

RESULTS

Compared with traditional one-dimensional (1D) chromatography, 2D chromatography has unique advantages in terms of peak capacity and resolution, and it is more effective for screening and identifying bioactive components of complex natural products.

CONCLUSION

Screening of natural bioactive components using 2D chromatography helps separation and analysis of complex samples with greater targeting and relevance, which is very important for development of innovative drug leads.

Biomolecule-Enabled Liquid Separation Membranes: Potential and Recent Progress

The implementation of membrane surface modification to enhance the performance of membrane-based separation has become a favored strategy due to its promise to address the trade-off between water permeability and salt rejection as well as to improve the durability of the membranes. Tremendous work has been committed to modifying polymeric membranes through physical approaches such as surface coating and ontology doping, as well as chemical approaches such as surface grafting to introduce various functional groups to the membrane. In the context of liquid separation membranes applied for desalination and water and wastewater treatment, biomolecules have gained increasing attention as membrane-modifying agents due to their intriguing structural properties and chemical functionalities. Biomolecules, especially carbohydrates and proteins, exhibit attractive features, including high surface hydrophilicity and zwitterionic and antimicrobial properties that are desired for liquid separation membranes. In this review, we provide an overview of the recent developments in biomolecule-enabled liquid separation membranes. The roles and potentials of some commonly explored biomolecules in heightening the performance of polymeric membranes are discussed. With the advancements in material synthesis and the need to answer the call for more sustainable materials, biomolecules could serve as attractive alternatives for the development of high-performance composite membranes.

Effect of Polyphenylsulfone and Polysulfone Incompatibility on the Structure and Performance of Blend Membranes for Ultrafiltration

This study deals with the modification of polyphenylsulfone ultrafiltration membranes by introduction of an incompatible polymer polysulfone to the polyphenylsulfone casting solution to improve the permeability. The correlation between properties of the blend polyphenylsulfone/polysulfone solutions and porous anisotropic membranes for ultrafiltration prepared from these solutions was revealed. The blend polyphenylsulfone/polysulfone solutions were investigated using a turbidity spectrum method, optical microscopy and measurements of dynamic viscosity and turbidity. The structure of the prepared blend flat sheet membranes was studied using scanning electron microscopy. Membrane separation performance was investigated in the process of ultrafiltration of human serum albumin buffered solutions. It was found that with the introduction of polysulfone to the polyphenylsulfone casting solution in N-methyl-2-pyrrolidone the size of supramolecular particles significantly increases with the maximum at (40–60):(60:40) polyphenylsulfone:polysulfone blend ratio from 76 nm to 196–354 nm. It was shown that polyphenylsulfone/polysulfone blend solutions, unlike the solutions of pristine polymers, are two-phase systems (emulsions) with the maximum droplet size and highest degree of polydispersity at polyphenylsulfone/polysulfone blend ratios (30–60):(70–40). Pure water flux of the blend membranes passes through a maximum in the region of the most heterogeneous structure of the casting solution, which is associated with the imposition of a polymer-polymer phase separation on the non-solvent induced phase separation upon membrane preparation. The application of polyphenylsulfone/polysulfone blends as membrane-forming polymers and polyethylene glycol (M_n = 400 g·mol⁻¹) as a pore-forming agent to the casting solutions yields the formation of ultrafiltration membranes with high membrane pure water flux (270 L·m⁻²·h⁻¹ at 0.1MPa) and human serum albumin rejection of 85%.