Crystalline polysaccharides are useful for important and rapidly growing applications ranging from advanced energy storage, green electronics, and catalyst or enzyme supports to tissue engineering ...and biological devices. However, the potential value of chitin in such applications is currently neglected because of its poor swellability, reactivity, and solubility in most commonly used solvents. Here, a high‐efficiency, energy‐saving, and “green” route for the fabrication of extremely strong and transparent chitin films is described in which chitin is dissolved in an aqueous KOH/urea solution and neutralized in aqueous ethanol solution. The neutralization temperature, ethanol concentration, and chitin solution deacetylation time are critical parameters for the self‐assembly of chitin chains and for tuning the morphology and aggregate structures of the resulting chitin hydrogels and films. Moreover, the drawing orientation can produce extremely strong and tough chitin films with a tensile strength, Young's modulus, and work of fracture of 226 MPa, 7.2 GPa, and 20.3 MJ m−3, respectively. The method developed here should contribute to the utilization of seafood waste and, thereby, to the sustainable use of marine resources.
Extremely strong and transparent chitin films are prepared using a high‐efficiency, energy‐saving, and “green” route in which chitin is dissolved in an aqueous KOH/urea solution. The chitin films exhibit high strength and high toughness with a tensile strength, Young's modulus, and work of fracture of 226 MPa, 7.2 GPa, and 20.3 MJ m−3, respectively. This method should contribute to the development of sustainable marine resources.
Polysaccharide‐based hydrogels have multiple advantages because of their inherent biocompatibility, biodegradability, and non‐toxicic properties. The feasibility of using polysaccharide‐based ...hydrogels could be improved if they could simultaneously fulfill the mechanical property and cell compatibility requirements for practical applications. Herein, the construction of double‐cross‐linked (DC) cellulose hydrogels is described using sequential chemical and physical cross‐linking, resulting in DC cellulose hydrogels that are mechanically superior to single‐cross‐linked cellulose hydrogels. The formation and spatial distribution of chemically cross‐linked domains and physically cross‐linked domains within the DC cellulose hydrogels are demonstrated. The molar ratio of epichlorohydrin to anhydroglucose units of cellulose and the concentration of the aqueous ethanol solution are two critical parameters for obtaining mechanically strong and tough DC cellulose hydrogels. The mechanical properties of the DC cellulose hydrogels under loading‐unloading cycles are described using compression and tension models. The possible toughening mechanism of double‐cross‐linking is discussed.
Double‐cross‐linked (DC) cellulose hydrogels are fabricated by a sequential chemical and physical cross‐linking strategy. The irreversible covalent cross‐linkings, cellulose II crystallite hydrates, together with the chain entanglements and strong hydrogen bonding interactions between cellulose chains endow the DC cellulose hydrogels with high strength, high toughness, and good recoverability.
High‐flexibility, high‐toughness double‐cross‐linked (DC) chitin hydrogels are prepared through a sequential chemical and physical cross‐linkings strategy. The incorporation of chemically and ...physically cross‐linked domains imbues the DC chitin hydrogels with relatively high stiffness, high toughness, and toughness recoverability.
Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic-aromatic amino acids sequence of proteins ...even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation-aromatic sequences can be synthesized through cation-π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.
Microalgae are excellent biological factories for high-value products and contain biofunctional carotenoids. Carotenoids are a group of natural pigments with high value in social production and human ...health. They have been widely used in food additives, pharmaceutics and cosmetics. Astaxanthin, β-carotene and lutein are currently the three carotenoids with the largest market share. Meanwhile, other less studied pigments, such as fucoxanthin and zeaxanthin, also exist in microalgae and have great biofunctional potentials. Since carotenoid accumulation is related to environments and cultivation of microalgae in seawater is a difficult biotechnological problem, the contributions of salt stress on carotenoid accumulation in microalgae need to be revealed for large-scale production. This review comprehensively summarizes the carotenoid biosynthesis and salinity responses of microalgae. Applications of salt stress to induce carotenoid accumulation, potentials of the Internet of Things in microalgae cultivation and future aspects for seawater cultivation are also discussed. As the global market share of carotenoids is still ascending, large-scale, economical and intelligent biotechnologies for carotenoid production play vital roles in the future microalgal economy.
Based on the principle of Contactless Conductivity Detection (CCD), a new contactless cross-correlation velocity measurement system with a three-electrode construction is developed in this work and ...applied to the contactless velocity measurement of gas-liquid two-phase flow in small channels. To achieve a compact design and to reduce the influence of the slug/bubble deformation and the relative position change on the velocity measurement, an electrode of the upstream sensor is reused as an electrode of the downstream sensor. Meanwhile, a switching unit is introduced to ensure the independence and consistency of the upstream sensor and the downstream sensor. To further improve the synchronization of the upstream sensor and the downstream sensor, fast switching and time compensation are also introduced. Finally, with the obtained upstream and downstream conductance signals, the velocity measurement is achieved by the principle of cross-correlation velocity measurement. To test the measurement performance of the developed system, experiments are carried out on a prototype with a small channel of 2.5 mm. The experimental results show that the compact design (three-electrode construction) is successful, and its measurement performance is satisfactory. The velocity range for the bubble flow is 0.312-0.816 m/s, and the maximum relative error of the flow rate measurement is 4.54%. The velocity range for the slug flow is 0.161 m/s-1.250 m/s, and the maximum relative error of the flow rate measurement is 3.70%.
In recent years, CID sensors have displayed great development potential in parameter measurement of gas-liquid two-phase flow in small channels. However, the fundamental/mechanism research on the ...response characteristics of CID sensors is relatively insufficient. This work focuses on the investigation of the influence of separation distance between slugs on the impedance (real part, imaginary part and amplitude) response characteristics of slug flow in small channels. Experiments were carried out with the CID sensors in four small channels with inner pipe diameters of 1.96 mm, 2.48 mm, 3.02 mm and 3.54 mm, respectively. The experimental results show that for a CID sensor, the slug separation distance has significant influence on the impedance response characteristics. There is a critical value of slug separation distance. When the slug separation distance is larger than the critical value, the impedance response characteristics of each slug can be considered independent of each other, i.e., there is no interaction between the slugs. When the slug separation distance is less than the critical value, the impedance response characteristics show obvious interaction between the slugs. It is indicated that the ratios of the critical values to the pipe inner diameters are approximate 100.
The objective of this study was to document and compare the lipid class and fatty acid composition of the green microalga
Chlorella zofingiensis cultivated under photoautotrophic and heterotrophic ...conditions. Compared with photoautotrophic cells, a 900% increase in lipid yield was achieved in heterotrophic cells fed with 30
g
L
−1 of glucose. Furthermore heterotrophic cells accumulated predominantly neutral lipids (NL) that accounted for 79.5% of total lipids with 88.7% being triacylglycerol (TAG); whereas photoautotrophic cells contained mainly the membrane lipids glycolipids (GL) and phospholipids (PL). Together with the much higher content of oleic acid (C18:1) (35.2% of total fatty acids), oils from heterotrophic
C. zofingiensis appear to be more feasible for biodiesel production. Our study highlights the possibility of using heterotrophic algae for producing high quality biodiesel.
► Cane molasses can be transformed by Chlorella to oils and astaxanthin. ► Molasses with metal removal supported better growth than glucose. ► Crude molasses could be directly used by optimizing ...culture conditions. ► Molasses up-regulated key enzymes involved in oil and astaxanthin biosynthesis. ► Typing oils to astaxanthin enables profitable biodiesel from algae.
The aim of this study is to evaluate the industrial waste cane molasses as a carbon source for cell growth, lipid and astaxanthin production of Chlorella zofingiensis. Pretreated with cation exchange resin to remove the metal ions, cane molasses provided better productivities of biomass, lipid, and astaxanthin (1.55, 0.71gL−1day−1 and 1.7mgL−1day−1, respectively) than glucose. Using a strategy of semi-continuous cultures coupled with feeding at a low concentration, molasses without pretreatment has the same effect as pretreated one on supporting the algal cell growth, lipid and astaxanthin production. The efficient metabolism of molasses triggered the up-regulation of genes involved in fatty acid and also astaxanthin biosynthesis, leading to the very high production of the two metabolites. This study highlights the possibility of using C. zofingiensis to deal with industrial wastes and to produce profitable biodiesel as well as the high-value astaxanthin.
The marine thraustochytrids are a promising source of docosahexaenoic acid (DHA) and the ketocarotenoid astaxanthin. In this study, the biosynthetic pathways of these two important metabolites in
sp. ...SK4 was illustrated by the analyses of the genome, transcriptome, key enzymes, and pathway products. Two sets of genes were involved in two pathways for the biosynthesis of fatty acids. The absence of
genes and the presence of docosapentaenoic acid (DPA), up to 12% of total fatty acids suggest that
sp. SK4 may synthesize DHA mainly via a polyketide synthase (PKS) pathway. Three enzymes, namely geranyl diphosphate synthase (GPPS), farnysyl diphosphate synthase (FPPS), and geranylgeranyle diphosphate synthase (GGPPS) were found to be involved in the formation of GGPP that was subsequently catalyzed to β-carotene by a trifunctional CrtIBY enzyme. β-Carotene might be ketolated and then hydroxylated into astaxanthin based on the carotenoid profiles. The formation of GGPP was proposed to be the limiting steps for carotenoid production. Overexpression of the
GPS together with the
isopentenyl pyrophosphate isomerase, and
hemoglobin resulted in not only 1.85- and 5.02-fold increases of total carotenoids and astaxanthin, but also 2.40- and 2.74-fold increases of total fatty acids and DHA. This study provides insights into the biosynthesis of carotenoids and fatty acids in
.
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