Preparation and structural properties of starch phosphate modified by alkaline phosphatase

An antibacterial packaging film based on amylose starch with quaternary ammonium salt chitosan and its application for meat preservation

A new generation of food packaging films is gradually replacing traditional plastic packaging films because of their biodegradability, safety, and some functional properties such as anti-bacterial and oxidant resistance. In the present work, an antibacterial packing film based on amylose starch and 2-hydroxypropyl-trimethylammonium chloride chitosan (HTCC) was prepared for meat preservation. The interfacial bonding mechanism between amylose, HTCC, and glutaraldehyde (GA) was determined experimentally and through molecular dynamics (MD) simulation. The macromolecular chains of amylose starch and HTCC became entangled via inter-molecular H-bonds and then cross-linked with GA via the Schiff base reaction. The interaction of amylose starch and HTCC improved the mechanical properties of the amylose films. Compared with the amylose films, the tensile strength and elongation at break of the optimal HTCC/amylose films reached to 16.13 MPa (an increase of 206.65 %) and 53.86 % (an increase of 109.49 %). The HTCC/amylose films were found to provide obvious bacteriostatic performance, a relatively low cytotoxicity, the lower transmittance in the UV region, and thus the ability to enhance the preservation of fresh meat. These excellent characteristics therefore suggest that HTCC/amylose films might be promising candidates for application in antibacterial food packaging films.

Research Progress in Modifications, Bioactivities, and Applications of Medicine and Food Homologous Plant Starch

Starchy foods are an essential part of people's daily diet. Starch is the primary substance used by plants to store carbohydrates, and it is the primary source of energy for humans and animals. In China, a variety of plants, including edible medicinal plants, such as Pueraria root, yam tuber and coix seed, are rich in starch. However, limited by their inherent properties, kudzu starch and other starches are not suitable for the modern food industry. Natural starch is frequently altered by physical, chemical, or biological means to give it superior qualities to natural starch as it frequently cannot satisfy the demands of industrial manufacturing. Therefore, the deep processing market of modified starch and its products has a great potential. This paper reviews the modification methods which can provide excellent functional, rheological, and processing characteristics for these starches that can be used to improve the physical and chemical properties, texture properties, and edible qualities. This will provide a comprehensive reference for the modification and application of starch from medicinal and edible plants.

Low-Cytotoxicity, Broad-Spectrum Corn Starch-Based Antibacterial Particles that Inhibit Multidrug-Resistant Bacteria

Antimicrobial resistance is a serious problem in biomedical applications that seriously increases the risk of medical failure. Therefore, developing highly efficient antibacterial agents that inhibit the growth of multidrug-resistant bacteria is a long-standing research goal. In this report, a low-cytotoxicity and highly efficient alternative to antibiotics was designed and prepared using edible corn starch as the scaffold and 2-hydroxypropyl-trimethylammonium chloride chitosan (HTCC) as the antimicrobial agent. The HTCC/starch particles were found to have a positively charged surface over a wide pH range and to possess broad-spectrum and highly efficient antimicrobial properties. These particles inhibited the growth of standard Gram-positive and Gram-negative bacteria from the China Pharmacopoeia and a clinical multidrug-resistant bacterial strain. Moreover, after treating the HTCC/starch particles with simulated gastric fluid (SGF, pH 1.2) for 4 h, the growth of clinical multidrug-resistant Escherichia coli (NT 2036) was inhibited effectively, indicating that these particles tolerate a gastric acid environment. Although the mass of SGF-treated HTCC/starch particles required to achieve similar antibacterial activity was ∼20-fold that of chloramphenicol or ampicillin, antibiotic-containing products require considerable amounts of pharmaceutical excipients to prepare. Therefore, the HTCC/starch particles described herein are potentially cost-effective alternatives to antibiotics that resolve the antimicrobial resistance issue, especially for inhibiting the growth of pathogenic intestinal bacteria.

Starch wall of urea: Facile starch modification to residue-free stable urea coating for sustained release and crop productivity

Quick leaching of urea fertilizer encourages different coatings, but achieving a stable coating without toxic linkers is still challenging. Here, the naturally abundant bio-polymer, i.e., starch, has been groomed to form a stable coating through phosphate modification and the support of eggshell nanoparticles (ESN) as a reinforcement agent. The ESN offers a calcium ion binding site for the phosphate to cause bio-mimetic folding. This coating retains hydrophilic ends in the core and gives an excellent hydrophobic surface (water contact angle 123°). Further, the phosphorylated starch+ESN led the coating to release only ∼30 % of the nutrient in the initial ten days and sustained for up to 60 days to show ∼90 % release. The stability of the coating has been attributed to its resistance to major soil factors viz., acidity and amylase degradation. The ESN also increases elasticity, cracking control, and self-repairing capacity by serving as buffer micro-bots. The coated urea enhanced the yield of rice grain by ∼10%.

Positively Charged-Amylose-Entangled Au-Nanoparticles Acting as Protein Carriers and Potential Adjuvants to SARS-CoV-2 Subunit Vaccines

The COVID-19 pandemic continues to spread worldwide. To protect and control the spread of SARS-CoV-2, varieties of subunit vaccines based on spike (S) proteins have been approved for human applications. Here, we report a new subunit vaccine design strategy that functions as both an antigen carrier and an adjuvant in immunization to elicit high-level immune responses. The complex of 2-hydroxypropyl-trimethylammonium chloride chitosan and amylose entangles Au nanoparticles (HTCC/amylose/AuNPs) forming 40 nm nanocarriers with a positive charge. The obtained positively charged nanoparticles reveal many merits, including the larger S protein loading capacity in PBS buffer, higher cellular uptake ability, and lower cell cytotoxicity, supporting their potential as safe vaccine nanocarriers. Two functionalized nanoparticle subunit vaccines are prepared via loading full-length S proteins derived from SARS-CoV-2 variants. In mice, both prepared vaccines elicit high specific IgG antibodies, neutralize antibodies, and immunoglobulin IgG1 and IgG2a. The prepared vaccines also elicit robust T- and B-cell immune responses and increase CD19⁺ B cells, CD11C⁺ dendritic cells, and CD11B⁺ macrophages at the alveoli and bronchi of the immunized mice. Furthermore, the results of skin safety tests and histological observation of organs indicated in vivo safety of HTCC/amylose/AuNP-based vaccines. Summarily, our prepared HTCC/amylose/AuNP have significant potential as general vaccine carriers for the delivery of different antigens with potent immune stimulation.

The molecular structure effects of starches and starch phosphates in the reverse flotation of quartz from hematite

Native starches and their phosphates with various molecular structures was introduced as the depressant to realize the flotation of quartz from hematite in this study. The present starch phosphates (WSP, NSP, GSP) were modified by the reaction between phosphate and three different corn starches (WS, NS, G50). The synthesis and characterization of starch phosphates found that starch with high amylopectin content was easily modified into starch phosphates. Microflotation tests showed that starch phosphates exhibited stronger depressing abilities of hematite flotation than native starches. Zeta potential measurement showed that both starches and starch phosphates could positively shift the zeta potential of hematite, while starch phosphates had more effects than starches. XPS and MDS indicated that the chemisorption occurred between Fe of hematite surface and CO groups of starch-based depressants. In addition, starch phosphates could adsorb onto the hematite surface through PO groups. MDS also presented that the adsorption strength of starch phosphate was mainly determined by the type and number of generating chelating rings, and the molecular structure of starch significantly affected the formation of chelate rings. The proposed adsorption model insights will significantly promote the development of starch-based depressants for iron ore flotation and other mineral processing applications.