With the rapid development of aquaculture towards scale, the healthy problems of aquatic animals caused by the abuse of antibiotics had become increasingly prominent. Therefore, the development of green and efficient alternatives to antibiotics had emerged. Plant polyphenols had become one of the excellent alternatives of antibiotics, because of their effects of promoting growth, antioxidant, antibacterial, anti-inflammatory and promoting intestinal health, as well as no side effects and drug residues. According to the results of relevant studies, plant polyphenols in appropriate dosage had a positive effect on the growth and physiological status of aquatic animals. This article summarized research advances on the effects of plant polyphenols on the growth performance, antioxidant capacity, anti-inflammatory, antibacterial and intestinal health of aquatic animals.
Solvent liquefaction was an effective process which could utilize biomass raw materials efficiently and comprehensively. Compared with water as a single solvent, the mixed solvent system could reduce the reaction temperature and pressure, improve the conversion of biomass, reduce the oxygen content in bio-oil, and increase the yield of the target product. This paper reviewed the common water mixed solvent systems in recent years, including the role of alcohol-water cosolvent, polar aprotic solvent-water system and ionic liquid-water system in the degradation process of lignocellulosic biomass, especially the application characteristics of ethanol-water cosolvent, tetrahydrofuran (THF)-water cosolvent and γ-valerolactone (GVL)-water cosolvent in biomass liquefaction. This paper also gave the shortage and suggestions of these solvents in biomass liquefaction field. Finally, based on the consideration of the economic value, recovery and safety performance of the solvent itself, it is pointed out that the development of low-cost, environment-friendly and sustainable liquefying solvents would be the key development direction in the future.
Lignin oligomers were prepared by ultrasonic-assisted depolymerization using corn cob lignin as raw material. The effects of depolymerization conditions on the yield and relative molecular mass of lignin oligomers were investigated, and the lignin oligomers were characterized by gel permeation chromatography(GPC), infrared spectroscopy(FT-IR), two-dimensional nuclear magnetic resonance spectroscopy (2D-HSQC NMR) and nuclear magnetic resonance phosphorus spectroscopy (31P NMR). The results showed that the yield of resultant lignin oligomer reached 40.2% and the number-average molecular weight ( Mn) of obtained lignin oligomer was 710 under the conditions of ultrasonic treatment (frequency 40 kHz, power 240 W) for 3 h and the solid-liquid ratio of lignin to solvent 200:1(g: L) in methanol/water (4:1, v: v) solvent system. The polydispersity index (PDI) was 1.62, which reserved the main molecular structure units of lignin, and the total hydroxyl content was 10.49 mmol/g.
Traditional polymer materials were divided into thermoplastic materials and thermoset materials. Thermoplastic materials could be processed twice but not rigid enough, and thermoset materials were rigid but difficult to recycle. The glass-like polymer material was between thermoplastic material and thermosetting material, which was a kind of material with high crosslinking density network and could be processed twice. Based on the network exchange mechanism of Vitrimer, this paper focused on the development history and research progress of bio-based glass polymers. Bio-vitrimers based on different covalent bonds were introduced in detail. Generally, the conditions of dynamic transesterification reaction were relatively mild, the reaction speed was fast, and the reaction materials were extensive, while the mechanical properties and reversibility of materials were poor. The reversibility and controllability of dynamic disulfide bond exchange were better, and the reaction was not harsh to the external acid-base environment, while the reaction substrate generally had toxic behavior and pungent odor. Dynamic imine bond exchange could make the material had good mechanical properties and durability, and good biocompatibility, while the reaction conditions and raw material selection were relatively simple. The application and advantages of bio-based Vitrimer materials were reviewed. The introduction of dynamic covalent bonds made up for the shortcomings of traditional 3D printing materials, such as insufficient rigidity and single function, enhanced the comprehensive performance of carbon fiber composites, and improved the service life and self-healing efficiency of elastomer materials. Finally, the paper gived a prospect of the future development.
Chitosan (CS) was modified by amidation with 7-hydroxycoumarin to improve its water solubility and enhance the bacteriostatic property by reducing the hydrogen bonding between chitosan molecules. 7-Hydroxycoumarin was firstly acylated by oxalyl chloride as a linker, and then coumarin was grafted onto chitosan molecules through a non-homogeneous amidation reaction to produce 7-hydroxycoumarin acylation-modified chitosan (CS-C). The coumarin-modified chitosan products were characterized by infrared spectrometry (FT-IR), X-ray diffraction (XRD) instrument, and thermal gravimetry, etc., for the solubility, antibacterial activity, crystalline, and thermal stability. The results showed that the chitosan had been amidated by coumarin, and the modified groups were mainly in the NH2 and chloride as well as ester bonds. The highest degree of substitution of NH2 was found when the mass ratio of chitosan to coumarin was 1:3, and the solubility mass fraction of the CS-C-3 prepared in this case could reach 79% in a neutral environment. Its bacteriostatic property was better than that of CS, with a minimum inhibitory concentration (MIC) of 0.5 g/L for Escherichia coli and a MIC of 1 g/L for Staphylococcus aureus. A minimum bactericidal concentration (MBC) value of 4 g/L for E. coli and a MBC value of 2 g/L for S. aureus.
