Green extraction of chitin from hard spider crab shells.

A green protocol to extract chitin from crab shells using water soluble ionic liquids (ILs) is here reported. Compared to conventional multistep acid-base extraction methods, this one-pot procedure achieves pulping of recalcitrant crustacean waste shells by employing ammonium acetate, ammonium formate and hydroxylammonium acetate as water-soluble, low-cost and easy to prepare ILs. An extensive parametric analysis of the pulping process has been carried out with different ILs, different ratios, temperature and time. The optimized protocol provides a high-quality chitin comparable, if not better, to commercial chitin. The best results were obtained at 150 °C with ammonium formate prepared in-situ from aqueous ammonia and formic acid: chitin was isolated in a 17 wt% yield (based on dried crab shells as starting biowaste), a degree of acetylation (DA) > 94 %, a crystallinity index of 39-46 %, a molecular weight up to 6.6 × 105 g/mol and a polydispersity of ca 2.0.

Fiddler crabs (Tubuca arcuata) as bioindicators of microplastic pollution in mangrove sediments.

In recent years, microplastics (MPs) have been widely found in the environment and pose potential risks to ecosystems, which attracted people's attention. Using bioindicators has been a great approach to understanding the pollution levels, bioavailability, and ecological risks of pollutants. However, only few studies have investigated MPs in mangrove ecosystems, with few bioindicators of MPs. Herein, the distribution of MPs in mangrove sediments and fiddler crabs (Tubuca arcuata) in mangroves was investigated. Results showed that the abundance values of MPs are 1160‒12,120 items/kg and 11-100 items/ind. in mangrove sediments and fiddler crabs, respectively. The dominant shape of MPs detected in mangrove sediments and fiddler crabs was fragments with sizes of 20‒1000 µm, larger MPs of 50-1000 µm were found in abundance. Polypropylene (PP), which is one of the most commonly used plastic materials, was the main polymer type. The distribution of MPs in fiddler crabs closely resembled that in surface mangrove sediments with a strong linear correlation (R2 > 0.8 and p < 0.05) between their abundance. Therefore, the MP contamination level in mangrove sediments can be determined by studying MP pollution in fiddler crabs. Moreover, the results of the target group index (TGI) indicated that fiddler crabs prefer feeding specific MPs in mangrove sediments. Our findings demonstrate the suitability of fiddler crabs as bioindicators for assessing MP pollution in mangrove sediments.

Microplastic from beach sediment to tissue: a case study on burrowing crab Dotilla blanfordi.

Background: Microplastics (MPs) are pervasive pollutants in the marine environment, exhibiting persistence in coastal sediment over extended periods. However, the mechanism of their uptake by marine organisms and distribution in habitat is less understood. The objective of the present study was to investigate the presence of MP contamination in burrow sediment, feeding pellets, and tissue of Dotilla blanfordi in the Gulf of Kachchh, Gujarat State. Methods: A total of 500 g of burrow sediment, 100 g of feeding pellets, and body tissue of 10 resident D. blanfordi were pooled as one replica. Such seven replicas from each site were analyzed for MP extraction from three sites, including Asharmata, Mandvi, and Serena, located in the Gulf of Kachchh. The standard protocol was used during the analysis of the collected samples in order to isolate MPs. Results: The abundance of MP was found higher in burrow sediment, feeding pellets and tissue of D. blanfordi at study site Mandvi, followed by Serena and Asharmata. The abundance of MP was found higher in D. blanfordi tissue, followed by burrow sediment and feeding pellet. A significant variation was observed in MP abundance among burrow sediment, feeding pellets, and tissue. MPs with various shapes (fiber, film, and fragment), sizes (1-2, 2-3, 3-4, and 4-5 mm), and colors (blue, green, black, pink, purple, red transparent) were recorded from all the study sites. Polyurethane and polyvinyl chloride were recognized as the chemical profile of the extracted MPs. The current investigation revealed greater accumulation of MPs in D. blanfordi's tissues compared to sediment and pellets, suggesting a risk of MP contamination in marine benthic fauna with a greater rate of bioaccumulation. D. blanfordi plays a significant role as a structuring agent for MP distribution in the intertidal flat through burrowing activity.

Elucidation of key fatty aroma compound contributing to the hepatopancreas of Eriocheir sinensis using sensomics approach by GC-IMS and GC-MS-O.

Aroma is one of the most noticeable characteristics when consuming Chinese mitten crab (Eriocheir sinensis) and is crucial for consumer satisfaction and the development of industry. In this study, we utilized fingerprints and the sensomics approach to analyze volatiles in the hepatopancreas of E. sinensis from Chongming and Taixing. GC-IMS indicated that the odor profile was dominated by pungent (-), buttery (+), and fruity (+) from Chongming and was more prone to alcoholic (-), solvent (-), and aldehydic (+) in Taixing. Moreover, PLS-DA modeling identified 2-acetylthiazole and toluene as the primary differential compounds. Subsequently, fifteen active-aroma compounds with FD values of >4 was recombined in an odorless matrix to simulate the odor profile of the hepatopancreas. Notably, removing methional may significantly decrease the intensity of the fatty and toasted odors. The findings reveal the odor profile of hepatopancreas and establish a theoretical foundation for subsequent studies on flavor.

Simultaneous monitoring of multiple prohibited drugs in various aquatic products.

Both sedative and antipathogenic drugs are often found to be illegally used in aquaculture, but there is a lack of simultaneous monitoring methods. A method for simultaneously monitoring multiple prohibited drugs in various aquatic product samples was developed in this work, including fish, shrimp, crab, and shellfish. Sulfonic acid-functionalized magnetic graphitic carbon nitride (S-MGCN) was synthesized and validated to efficiently co-extract all targets (adsorption efficiency over 90.07%) through various adsorption mechanisms such as electrostatic interaction, hydrogen bonding, and π-π interaction while demonstrating good sample matrix purification ability (matrix effect below 13.60%). A new magnetic solid-phase extraction method based on S-MGCN was subsequently established. Coupled with UPLC-MS/MS, the detection limits were 0.030.075 µg /kg, and the recoveries ranged from 88.76% to 111.74% with the RSDs lower than 14.60%, indicating that the developed method has good sensitivity, accuracy, and precision. Further validation of its practicality was achieved through actual sample analysis.

Isolation, characterization and antimicrobial properties of hepatopancreas lectin of the freshwater crab Oziotelphusanaga.

Lectins are versatile proteins that specifically recognize and interact with sugar moieties expressed on the cell surface. The potential of lectin in drug targeting and delivery has instigated interest to identify natural lectins. Crabs have been identified as a rich source of lectin because the innate immune system is activated on encounter of pathogens and helps in the production of lectin. Although the presence of lectins in crab's hemolymph is well documented, little information about lectin in hepatopancreas, a vital organ for immunity and digestion in crustaceans, is currently available. A calcium dependent lectin (75 kDa) was purified from the hepatopancreas of the freshwater crab Oziotelphusa naga by bioadsorption and fetuin linked Sepharose 4B affinity chromatography technique. The isolated hepatopancreas lectin is calcium dependent and maximum agglutination was observed with rabbit erythrocytes. The hemagglutinating activity of the hepatopancreas lectin was effectively inhibited by sugars, such as α-lactose, GlcNAc, trehalose and NeuAc. Compared to sialylated N-glycosylated proteins including transferrin and apo transferrin, sialylated O-glycosylated proteins like fetuin exhibited stronger inhibitory effect. The ability of erythrocytes to bind hepatopancreas lectin has been diminished by desialylation of the potent inhibitor, indicating the significance of sialic acid in lectin-ligand interactions. The purified hepatopancreas lectin showed a broad spectrum of antimicrobial activity against bacteria Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, E. coli and fungi Candida albicans and Aspergillus niger. The findings of this study demonstrate the significance of hepatopancreas lectin as a multifunctional defense protein that inhibits the growth of bacteria and fungi.

Metal binding feature of copper‒induced metallothionein from freshwater crab Sinopotamon henanense reveals its Cu‒thionein character.

Sinopotamon Henanense expresses two metal‒induced metallothioneins (MTs), Cd‒induced MT and Cu‒induced MT (ShCuMT). The Cd‒induced MT has been characterized as a Cd‒thiolate MT. However, it is unknown whether ShCuMT is a Cu‒thiolate MT. In the present study, ShCuMT was expressed heterologously in Escherichia coli and purified by Ni‒NTA column and superdex‒75 column. And its metal‒binding feature was evaluated by DTNB reaction, circular dichroism spectroscopy (CD), isothermal microtitration (ITC), electrospray flight mass spectrometry (ESI‒TOF‒MS), and matrix‒assisted laser desorption ionization flight mass spectrometry (MALDI‒TOF‒MS). Bioinformatics analysis demonstrated that ShCuMT possessed the cysteine‒triplet motif of a Cu‒specific MT. Expression and purification of ShCuMT illustrated that SUMO tag used as the production system for ShCuMT resulted in a high production yield. The stability order of ShCuMT binding metal ions were Cu (Ⅰ) > Cd (Ⅱ) > Zn (Ⅱ). The CD spectrum indicated that ShCuMT binding with Cu (I) exhibited a compact thiol metal clusters structure. Besides, there emerged no a visible nickel‒thiol absorption after Ni‒NTA column affinity chromatography. The ITC results implied that Cu‒ShCuMT possessed the optimal thermodynamic conformation and the highest stoichiometric number of Cu (Ⅰ). Overall, the results suggested that SUMO fusion system is a robust and inexpensive approach for ShCuMT expression and Ni‒NTA column had no influence on metal binding of ShCuMT and Cu(Ⅰ) was considered its cognate metal ion, and ShCuMT possessed canonical Cu‒thiolate characteristics. The metal binding feature of ShCuMT reported here contributes to elucidating the structure‒function relationship of ShCuMT in S. Henanense.

Temporal distribution of microplastics and other anthropogenic particles in four marine species from the Atlantic coast (France).

The characterization of microplastic (MP) contamination in marine species is increasing as concerns about environmental and food safety are more and more discussed. Here, we reported a quantitative and qualitative assessment of the contamination by anthropogenic particles (from visual sorting; AP) and MP (plastic-made) in the whole soft body or digestive tract of marine species. Four commercial species were studied, namely the Pacific oyster (Magallana gigas), the spiny spider crab (Maja sp.), the common sole (Solea solea) and seabass (Dicentrarchus labrax or punctatus). AP and MP uptake were studied over three to four seasons depending on the species. After tissues digestion, particles were extracted under a stereomicroscope and morphometric characteristics were reported. Then, polymers were identified by ATR-FTIR spectroscopy. Seasonal variations were mainly described in the Pacific oyster as AP uptake was lower in autumn and MP uptake was higher in spring. These variations may be linked to the reproduction and growth cycles of this species. Moreover, seabass ingestion was lower in autumn compared to winter. Contamination in spider crabs and soles showed either weak or no seasonal trends, both quantitatively and qualitatively. Overall, AP contamination in all studied species ranged from 1.17 ± 1.89 AP.ind-1 (in sole) to 4.07 ± 6.69 AP.ind-1 (in seabass) while MP contamination ranged from 0.10 ± 0.37 MP.ind-1 (in sole) to 1.09 ± 3.06 MP.ind-1 (in spider crab). Fibers were mostly reported in all species (at least 77.7%), along with cellulosic polymers (at least 43.7%). AP and MP uptake were detected in all species and at almost all seasons, with the only exception of the common sole during autumn. Therefore, this study emphasizes the ubiquity of AP and MP contamination in marine species and provides new knowledges about seasonal uptake by commercial species.

Investigation of the Alternations in the Muscle Quality of Swimming Crab (Ovalipes punctatus) during Cold-Chain Transportation Using Physicochemical and TMT-Based Quantitative Proteomic Analysis.

Physicochemical properties and protein alterations in Ovalipes punctatus during cold-chain transportation were examined via sensory scores, water-holding capacity (WHC), glucose (GLU) content, catalase (CAT) activity, urea nitrogen (UN) content, and tandem mass tag (TMT)-based proteomic analysis. The results revealed that sensory characteristics and texture of crab muscle deteriorated during transportation. Proteomic analysis revealed 442 and 470 different expressed proteins (DEPs) in crabs after 18 h (FC) and 36 h (DC) of transportation compared with live crabs (LC). Proteins related to muscle structure and amino acid metabolism significantly changed, as evidenced by the decreased WHC and sensory scores of crab muscle. Glycolysis, calcium signaling, and peroxisome pathways were upregulated in the FC/LC comparison, aligning with the changes in GLU content and CAT activity, revealing the stress response of energy metabolism and immune response in crabs during 0-18 h of transportation. The downregulated tricarboxylic acid (TCA) cycle and carcinogenesis-reactive oxygen species pathways were correlated with the decreasing trend in CAT activity, suggesting a gradual retardation in both energy and antioxidant metabolism in crabs during 18-36 h of transportation. Furthermore, the regulated purine nucleoside metabolic and nucleoside diphosphate-related processes, with the increasing changes in UN content, revealed the accumulation of metabolites in crabs.

Chitin extraction from crab shells and synthesis of chitin @metakaolin composite for efficient amputation of Cr (VI) ions.

The present research study combines chitin from shrimp waste with the oxide-rich metakaolin. Metakaolin is a blend of mixed oxides rich in silica and alumina with good adsorbent properties. The chitin@metakaolin (CHt@M.K.) composite was synthesized and characterized using FTIR, SEM, TGA, XRD and XPS techniques. Cr(VI) removal studies were compared for chitin and CHt@M.K. through adsorption. It was found that the adsorption capacity of CHt@M.K. is 278.88 mg/g, almost double that of chitin, at pH 5.0 in just 120 min of adsorption. Isotherm models like Langmuir, Freundlich, Temkin and Dubinin-Radushkevich were investigated to comprehend the adsorption process. It was revealed that Langmuir adsorption isotherm is most suitable to elucidate Cr(VI) adsorption on CHt@M.K. The adsorption kinetics indicate that pseudo first order was followed, indicating that the physisorption was the process that limited the sorption process rate. The positive enthalpy change (20.23 kJ/mol) and positive entropy change (0.083 kJ/mol K) showed that the adsorption process was endothermic and more random at the solid-liquid interface. The negative free energy change over entire temperature range was an indicator of spontaneity of the process. Apart from all these, the non-covalent interactions between Cr(VI) and composite were explained by quantum calculations based models.