A green approach to starch modification by solvent-free method with betaine hydrochloride

Quaternization of cassava starch and determination of antimicrobial activity against bacteria and coronavirus

This study describes the novel development of quaternized cassava starch (Q-CS) with antimicrobial and antiviral properties, particularly effective against the MHV-3 coronavirus. The preparation of Q-CS involved the reaction of cassava starch (CS) with glycidyltrimethylammonium chloride (GTMAC) in an alkaline solution. Q-CS physicochemical properties were determined by FTIR, NMR, elemental analysis, zeta potential, TGA, and moisture sorption. FTIR and NMR spectra confirmed the introduction of cationic groups in the CS structure. The elemental analysis revealed a degree of substitution (DS) of 0.552 of the cationic reagent on the hydroxyl groups of CS. Furthermore, Q-CS exhibited a positive zeta potential value (+28.6 ± 0.60 mV) attributed to the high positive charge density shown by the quaternary ammonium groups. Q-CS demonstrated lower thermal stability and higher moisture sorption compared to CS. The antimicrobial activity of Q-CS was confirmed against Escherichia coli (MIC = 0.156 mg mL-1) and Staphylococcus aureus (MIC = 0.312 mg mL-1), along with a remarkable ability to inactivate 99% of MHV-3 coronavirus after only 1 min of direct contact. Additionally, Q-CS showed high cell viability (close to 100%) and minimal cytotoxicity effects, guaranteeing its safe use. Therefore, these findings indicate the potential use of Q-CS as a raw material for antiseptic biomaterials.

Effects of dual modification by cationization and acetylation on the physicochemical and structural characteristics of glutinous rice starch

In this research, the effects of cationization, acetylation and dual modification by cationization and acetylation on the physicochemical and structural characteristics of glutinous rice starches were investigated. The rapid viscosity analyzer revealed a substantial increased paste viscosity post modification. Particularly, for dually modified starch, the peak viscosity increased from 3071.67 to 4082.00 cP. The freeze-thaw stability substantially enhanced, with both single cationic and dually-modified starches standing out by exhibiting no water syneresis even at 21 freeze-thaw cycles, while native starch exhibited higher syneresis, up to 74.55 %. Both single cationization and cationization-acetylation destroyed the starch granules, characterized by the roughness and cracks. But, for single acetylation, there was no notable changes on granules' morphology. Fourier transform infrared spectroscopy exhibited notable shifts after modification, both acetylation and dual modification, resulting in a new peak at 1728 cm-1. 13C cross-polarization magic angle spinning nuclear magnetic resonance spectra displayed new peaks at 52-55 and 19-22 ppm following cationization and acetylation, respectively. These structural alterations indicate the successful incorporation of functional groups during modification. Overall, this study provides valuable insights for the industrial utilization of these three modified glutinous rice starches.

Mechanism analysis of a novel natural cationic modified dextran flocculant and its application in the treatment of blue algal blooms

Blue algae, a type of harmful microalgae, are responsible for causing harmful algal blooms that result in severe environmental issues. To address this problem, a biopolysaccharide-based flocculant was developed for treating blue algae blooms. This flocculant was created by modifying high molecular weight dextran using the natural cationic monomer betaine (Dex-Bet), making it environmentally friendly. Various techniques were used to characterize the prepared Dex-Bet flocculant, including infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The effectiveness of the Dex-Bet flocculant was evaluated using kaolin-simulated wastewater. The results showed that the treated supernatant had a transmittance of up to 98.25 %. Zeta potential analysis revealed that the main mechanisms of flocculation were charge neutralization, charge patching, and adsorption bridging. The application of Dex-Bet in treating blue-green algae resulted in a maximum removal rate of 98.2 %. This study provides a potential flocculant for blue algae bloom treatment.

Alkaline Hydrolysis of Waste Acrylic Fibers Using the Micro-Water Method and Its Application in Drilling Fluid Gel Systems

Filtrate reducer is a drilling fluid additive that can effectively control the filtration loss of drilling fluid to ensure the safe and efficient exploitation of oilfields. It is the most widely used treatment agent in oilfields. Due to its moderate conditions and controllable procedure, alkaline hydrolysis of high-purity waste polyacrylonitrile has been utilized for decades to produce filtrate reducer on a large scale in oilfields. However, the issues of long hydrolysis time, high viscosity of semi-finished products, high drying cost, and tail gas pollution have constrained the development of the industry. In this study, low-purity waste acrylic fiber was first separated and purified using high-temperature hydroplastization, and the hydrolyzed product was obtained using alkaline hydrolysis with the micro-water method, which was called MW-HPAN. The hydrolysis reaction was characterized using X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis, and the elemental analysis showed a hydrolysis degree of 73.21%. The experimental results showed that after aging at 180 °C for 16 h, the filtration volume of the freshwater base slurry with 0.30% dosage and 4% brine base slurry with 1.20% dosage was 12.7 mL and 18.5 mL, respectively. The microstructure and particle size analysis of the drilling fluid gel system showed that MW-HPAN could prevent the agglomeration of clay and maintain a reasonable particle size distribution even under the combined deteriorating effect of high temperature and inorganic cations, thus forming a dense filter cake and achieving a low filtrate volume of the drilling fluid gel system. Compared with similar commercially available products, MW-HPAN has better resistance to temperature and salt in drilling fluid gel systems, and the novel preparation method is promising to be extended to practical production.

Solid state cationization reaction of microporous starch with betaine hydrochloride under repeated heating/cooling cycles: Design of a green approach for corn starch modification

In this research, the cationization process of microporous starch with betaine hydrochloride (BHC) in the presence of H3PO4 (as a catalyst) under heating/cooling cycles was reported for the first time. Granular microporous starch was initially prepared from normal corn starch (NS) through amyloglucosidase treatment. Then, solid state cationization reaction of microporous starch (MS) with betaine hydrochloride (BHC) was performed under repeated dry-heat modification. The cationic microporous starch showed higher substitution degree (0.031) and reaction efficiency (89.1 %) in comparison with cationic starch based on NS (0.021, 60.3 %), which this can be attributed to the increased probability of effective collision between BHC molecules and starch granules after enzymatic treatment. The analysis of cationic starches by FTIR and 13C NMR confirmed the presence of cationic functional groups on starch chains. Further examinations on the modified starches by single and dual treatments were accomplished with respect to morphology, particle size distribution, X-ray powder diffraction (XRD), colour parameters, zeta potential, amylose content, viscosity, solubility, and swelling power. The greenness of the suggested dual treatment (score: 82) in this work was evaluated and compared to a conventional method reported in literature (score: 67) on the preparation of cationic starches.