Crab Exoskeleton Research Articles

Reliability of the Young's modulus of crab exoskeleton materials estimated from nanoindentation tests

The local and global mechanical properties of a mineralized biological material using the mud crab as a model material were investigated and compared. The stress–strain (s–s) curves for wet and dry conditions of the endocuticle were exactly examined by performing tensile tests with strain gauges. The local properties were examined through nanoindentation testing (NI) in a dry condition. The global Young's modulus, E, evaluated from the slope of the linear part of the s–s curve, did not vary with wet or dry specimen conditions; however, the stress and strain required to fracture depended on the conditions. The E was compared with the results of property mapping obtained from NI. Due to local differences in the grade of mineralization in the exoskeleton, the mapping indicated that nanoindentation tests should be performed for an extensive region of the cuticle. The results will provide useful information for future material development based on biomimetics.

Enhanced strength, toughness and reliability in crab exoskeleton–inspired 3D-printed porous thermoplastics

PurposeFused deposition modeling enables multiscale structure control. However, most of this structural space is unexplored. Specifically, the impact of biomimetic porous structures on the mechanical behavior and reliability of common thermoplastics are unclear. In this work, porous structures inspired by the multifunctional crab exoskeleton were 3D-printed with different raster orientations, including fully rotating rasters similar to Bouligand structures found in biological materials. Tensile tests and simulations were performed to observe the stochastic behavior of fracture properties and to reveal the underlying origins of mechanical reliability in biomimetic porous systems.Design/methodology/approachTensile tests were performed on 3D-printed porous structures with four different rasters. These rasters were biomimetic Bouligand, semi-Bouligand, 00 raster and 45°/−45° raster. In addition, two different sets were manufactured to observe the impact of contours on the mechanical behavior. A total of 137 tensile tests were performed. A total of 88 finite element simulations were executed using Abaqus built-in Hashin damage initiation criterion and energy-based damage evolution law. Weibull analyses were performed to quantify the stochastic properties.FindingsBiomimetic Bouligand structure is effective in increasing fracture strength. Average fracture strength of the Bouligand structure was 33% higher compared to the default 45°/−45° and 10% higher compared to 00 rasters. Variations in strength were lower in Bouligand structure compared to the default 45°/−45° raster. However, 00 raster had the highest Weibull modulus m = 54 compared to Bouligand m = 25 and 45°/−45° m = 17. Simulations showed that Bouligand structure is effective in increasing the mechanical reliability through local damage accumulation around the holes. The simulated Weibull modulus of the Bouligand structure was 40 compared to the moduli of other rasters that ranged from 18 to 25.Practical implicationsThe mechanical reliability of porous Bouligand structures is higher compared to other rasters, which makes the biomimetic structure a better choice for industrial applications. Contours decrease the strength and strain at failure for 3D-printed porous structures. Bouligand structures with rotating raster orientations increased strength and strain at failure when contours are present in the porous structure.Originality/valueTo the best of the authors’ knowledge, this is the first study showing the effects of biomimetic raster orientations on the mechanical behavior and the effects of contours on the tensile fracture properties of 3D-printed porous acrylonitrile butadiene styrene using tensile tests and fracture simulations. This is the first study applying composite fracture model to anisotropic porous 3D-printed polymers.

The Blue Treasure: Comprehensive Biorefinery of Blue Crab (Callinectes sapidus).

The blue crab, Callinectes sapidus (Rathbun, 1896), has become an invading species in the Mediterranean region, almost completely replacing native species within a few years and causing significant loss to local production. In some areas, there is an urgent need to propose new supply chains based on blue crab exploitation, where the potential valorisation routes for unsaleable blue crab and waste play an important role. The final purpose is to transform a threat into a treasure, towards a more sustainable world. In addition to applications in food industries, the considerable quantity of bioactive compounds in by-products, such as polysaccharides, proteins, amino acids, carotenoids, and chitin, needs to be capitalised by means of efficacious strategies and appropriate management. Crab exoskeleton can also be exploited as a carbonaceous material with applications in several fields, including medicine. Blue crab bioactive molecules have been widely recognised for having antioxidant, anticancer, antidiabetic, anti-inflammatory, and antimicrobial properties. Due to these functional and distinctive activities, such high-value components could be employed in various industries such as food-feed-pharma and cosmetics. Recycling and reusing these underutilised but economically valuable waste or by-products could help to reduce the environmental impacts of the whole supply chain from the perspective of the circular economy.

Analysis of molecular structure and topological properties of chitosan isolated from crab shell and mushroom

This investigation aimed to scrutinize the chemical and structural analogies between chitosan extracted from crab exoskeleton (High Molecular Weight Chitosan, HMWC) and chitosan obtained from mushrooms (Mushroom-derived Chitosan, MRC), and to assess their biological functionalities. The resulting hydrolysates from the hydrolysis of HMWC by chitosanase were categorized as chitosan oligosaccharides (csCOS), while those from MRC were denoted as mrCOS. The molecular weights (MW) of csCOS and mrCOS were determined using Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry. Furthermore, structural resemblances of csCOS and mrCOS were assessed utilizing X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Intriguingly, no apparent structural disparity between csCOS and mrCOS was noted in terms of the glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) composition ratios. Consequently, the enzymatic activities of chitosanase for HMWC and MRC exhibited remarkable similarity. A topological examination was performed between the enzyme and the substrate to deduce the alteration in MW of COSs following enzymatic hydrolysis. Moreover, the evaluation of antioxidant activity for each COS revealed insignificance in the structural disparity between HMWC and MRC. In summary, grounded on the chemical structural similarity of HMWC and MRC, we propose the potential substitution of HMWC with MRC, incorporating diverse biological functionalities.

Total body burden of neurotoxicant Hg in Chinese mitten crab (Eriocheir sinensis) - Considerations of distribution and human risk assessment

The Chinese mitten crab (Eriocheir sinensis) is considered one of the 100 most invasive alien species in the world. Despite this, its role in ecosystems, among others, in the trophodynamics of pollutants including mercury, is still not fully understood. Becoming an increasingly important and widespread element of the trophic chain in new areas arouses interest from humans as consumers. Hence it is important to determine the level of contaminants (including Hg) in alien species. In the present study, great attention was paid separately to the soft tissues and hard tissues of the exoskeleton, which may play an important role in the detoxification of the crab's body from toxic Hg. The study was conducted on crabs collected in 2011–2021 in the Vistula Lagoon. Concentrations of total mercury and its forms were carried out using a Direct Mercury Analyzer, DMA-80 (Milestone, Italy). The present study showed that mercury accumulation of the crab's body largely occurred through the gills, followed by the oral route. The distribution of Hg in the crab's organs was related to the trophic origin of the mercury, while halide-bound mercury and semilabile forms from the respiration (filtration) process were redistributed into the crab's exoskeleton. Male crabs, compared to females, had a higher Hg burden on internal organs such as their hepatopancreas and gonads. Hg concentration in hard tissues was closely related to the type of mineralization of the carapace. The elimination of Hg from the muscles and from the hepatopancreas into the carapace was one of the important detoxification processes of the crab's body. Thus, moulting crabs effectively remove Hg protecting its body from the neurotoxin. As a result, a smaller Hg load is biomagnified, making the crab's muscle tissue fit for human consumption. The observed decrease in Hg concentrations from 2011 to 2021, as well as the spatial variability of Hg in the crab's muscles, testify that the crab can serve as a biomonitor for ecosystem changes.

Chitin-Derived Silver Nanoparticles for Enhanced Food Preservation: Synthesis, Characterization, and Antimicrobial Potential

In this research article we report the potentials of chitin-based silver nanoparticles (chitin AgNPs) derived from Indian mimic goatfish (Mulloidichthys ayliffe) scales as an effective food preservation agent. The study comprehensively presents the multifaceted attributes of chitin AgNPs, including their synthesis, characterization, and antimicrobial properties. Chitin yield from M. ayliffe scales and three-spot swimming crab (P. sanguinolentus) exoskeleton was determined, with the insoluble content quantified. FTIR analysis unveiled distinct absorption peaks for chitin, and scanning electron microscopy revealed the ultrastructure of chitin from both the sources. Using UV–visible spectroscopy, the biosynthesis of AgNPs was accomplished and characterized, with the color shift of the solution serving as proof of a successful synthesis. UV–vis spectra provided insights into nanoparticle size and shape. SEM micrographs exhibited spherical particle morphology, while FTIR spectra indicated amino group interactions contributing to AgNP stabilization. The antimicrobial potential of chitin AgNPs was assessed against the food pathogen, Vibrio spp. Chitin films displayed significant antimicrobial activity, particularly AgNP-synthesized chitin from M. ayliffe scales, demonstrated the highest Vibrio spp. inhibition activity. Furthermore, chitin AgNPs were incorporated into the common chili, Capsicum annuum and the tomato, Solanum lycopersicum to extend their shelf life at room temperature. This study reveals the efficacy of chitin AgNPs from M. ayliffe scales as potent agents for food preservation, offering insights into their physical, mechanical, and antimicrobial attributes. The application of chitin AgNPs to perishable food items highlights their potential in enhancing shelf life and quality, opening innovative avenues for sustainable food preservation.

Green fabrication of chitosan from marine crustaceans and mushroom waste: Toward sustainable resource utilization

Abstract The exoskeletons of crabs, shrimp, and fish are major waste. These wastes contain chitin, an abundant natural polymer found next to cellulose. Thus, disposal of this waste becomes a huge problem for the environment; besides this, reutilization boosts the circular economy. Chitin is partially deacetylated to yield the economically useful product of chitosan and is a heteropolymer. The current study isolated chitosan from mushrooms and various marine crustaceans, i.e., crabs, shrimp, and fish. Chitosan was extracted from marine crustaceans by demineralization, deproteination, and deacetylation. Later, extracted chitosan was characterized by physicochemical characteristics like deacetylation degree, ash content, protein, color, fat-binding capacity (FBC), water-binding capacity (WBC), pH, and moisture content. The result showed that chitosan yield ranges from 13.0% to 17.0%, the degree of deacetylation range from 82.0% to 85.0%, ash content range from 0.8% to 3.0%, and protein content is below 1.0%. The FBC and WBC range between 320% and 444% and 535% and 602%, respectively. The pH and moisture content range from 7.4 to 8.0 and from 2.0% to 4.0%, respectively. Overall, results specified that crustacean waste was an exceptional chitosan source with availability and production consistency.

Crab (<i>Brachyura</i>) shell acid and alkali treatments: Influence on thermal and structural properties of isolated acetamide-rich natural polymer

Exoskeleton of crab comprises a dominating mineral (calcium carbonate, CaCO3), protein and a natural polymer (chitin). Chemical treatments have been employed at different instances to isolate pure chitin from different sources. It is thus necessary to investigate how this treatment will influence the features of chitin isolated from the same source (crab). In this study, 0.4, 0.8 and 1.2 M hydrochloric acid (HCl) were separately used to demineralize crab shell particles and this was followed by deproteinization with 0.4 and 1.2 M sodium hydroxide (NaOH) at 100 °C. Results showed that chitin properties were influenced by concentrations of reagents. Fibrils of different forms and surface appearance were observed via Scanning Electron Microscopy (SEM). The highest crystallinity index of 71% was possessed by chitin extracted using 0.4 M HCl and NaOH while 65.5% remained the least displayed by chitin extracted with 1.2 M HCl and NaOH. This trend was similar for chitin’s thermal stability where Thermogravimetric analysis (TGA) results informed that using the highest concentrations of 1.2 M HCl and NaOH provided chitin with 80.12 kJ/mol activation energy. On the other hand, 112.54 kJ/mol was calculated for chitin isolated with the minimum demineralization and deproteinization reagents used in this study.

Comparative Analysis of Composition and Porosity of the Biogenic Powder Obtained from Wasted Crustacean Exoskeletonsafter Carotenoids Extraction for the Blue Bioeconomy

The recovery and recycling of wasted resources are at the forefront of contemporary global issues. Methods of addressing several different issues may go hand-in-hand with each other, such as linking food waste recycling into bio-based adsorbent materials and wastewater treatment. Crustacean exoskeletons are promising candidates for bio-friendly adsorbents; however, maximizing their efficiency requires the optimization of processing technology. Crustacean meat offers an (often luxury) culinary delicacy, while their waste exoskeletons offer opportunities for smart recycling of the magnesian calcite nanoporous biocomposite. Here, we conduct a structural characterization of the exoskeletons of three crustacean species to assess how the extraction of valuable carotenoids affects prospects for the further valorization of their porous powder. The exoskeleton powder’s composition and morphology were investigated by SEM, Raman spectroscopy, FTIR and XRD. The biomineral component magnesian calcite was recorded both in native and in post-extraction exoskeleton powder. Acetone extraction, however, partially removed organic matter from the exoskeletons, resulting in the porosity of the respective powder increasing significantly from below 10 m2 g−1 in the native powder to over 32 m2 g−1 in post-extraction samples of blue crab and spider crab exoskeletons—while the spiny lobster exoskeleton exhibited low porosity, as measured by the BET method. This new insight could improve exoskeleton processing in the sustainable circular economy and applied blue bioeconomy—most notably for adsorbent materials for pollutants dissolved in water or as ordered, nature-derived nanostructured templates.

Development of a Microbial-Assisted Process for Enhanced Astaxanthin Recovery from Crab Exoskeleton Waste

Astaxanthin is a xanthophyll carotenoid possessing impressive nutraceutical, antioxidant, and bioactive merits. Traditionally, astaxanthin is extracted from crustacean wastes via solvent extraction methods. However, the rigid structure of shells that comprise complex proteins and chitin challenges the extraction process. This investigation addressed an efficient microbial-assisted method to facilitate astaxanthin recovery from crab exoskeleton waste utilizing chitinolytic and proteolytic microorganisms. Herein, we evaluated the effect of pretreatment of the exoskeleton waste with a newly isolated probiotic strain, Bacillus amyloliquefaciens CPFD8, showing remarkable protease and chitinase activity and a proteolytic Saccharomyces cerevisiae 006-001 before solvent extraction, using acetone/hexane, on astaxanthin recovery. Furthermore, the antioxidant and anti-inflammatory activities of the recovered astaxanthin were inspected. Results revealed that both strains boosted the astaxanthin yield from the crab (Callinectes sapidus) exoskeleton compared with solvent extraction using acetone/hexane. Under optimum conditions, astaxanthin yield was 217 and 91 µg/g crab exoskeleton in samples treated with B. amyloliquefaciens CPFD8 and S. cerevisiae 006-001, respectively. Interestingly, pretreatment of crab exoskeleton waste with B. amyloliquefaciens CPFD8 yielded more than 6-fold astaxanthin compared with the solvent extraction method that yielded just 35 µg/g. This increase could be attributed to the proteolytic activity of B. amyloliquefaciens CPFD8 that rendered deproteinized shell chitin accessible to chitinase, facilitating the penetration of solvents and the recovery of astaxanthin. The recovered astaxanthin exhibited excellent antioxidant activity in scavenging DPPH or ABTS free radicals with IC50 values of 50.93 and 17.56 µg/mL, respectively. In addition, the recovered astaxanthin showed a remarkable anti-inflammatory impact on LPS-induced murine macrophage RAW264.7 cells and significantly inhibited the production of nitric oxide, TNF-α, and IL-6 compared with the untreated control. These findings suggest the potential use of the developed microbial-assisted method utilizing chitinolytic and proteolytic B. amyloliquefaciens CPFD8 to maximize the recovery of bioactive astaxanthin from crab (C. sapidus) exoskeleton waste.

Thermodynamic study of the adsorption of Cd2+ and Ni2+ onto chitosan – Silica hybrid aerogel from aqueous solution

Adsorption studies have been conducted on aqueous solution to investigate the effect of temperature on the sorption of Cd2+ and Ni2+ by Chitosan-silica hybrid aerogel [(CS)hA], which was developed using a blend of components from crab exoskeleton and bamboo biomass and synthesized using sol–gel method. The application of this derived aerogel for clean-up of water bodies polluted with heavy metals at varying temperatures was undertaken with a view to establish its effectiveness. The studied temperatures were 301 K, 308 K, 318 K, 328 K and 338 K at pH 3 and contact time of 180 mins and 60 mins for Cd2+ and Ni2+, respectively. Data obtained were subjected to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models which were used to evaluate the adsorption process. Langmuir Isotherm model proved to be the best fit in interpreting the adsorption process with the maximum Cd2+ sorption values within 57.14 to 57.80 mg g−1 while Ni2+ sorption values lie between 52.08 and 58.82 mg g−1. The effect of enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) on the sorption of Cd2+ and Ni2+ by the derived aerogel were also deduced. The process is spontaneous, exothermic with the studied ions well aligned on the derived aerogel surface.

Revealing the Shamefaced Crab Calappa granulata (Crustacea: Brachyura) from the Adriatic Sea, Northern Basin of the Mediterranean

This study presents the first data on morphometry, length–weight relationship, diet, reproductive biology, epibionts and genetic identity of the shamefaced crab Calappa granulata from the central eastern Adriatic Sea. A total of 92 crabs were collected during 2011, 2014 and 2015, of which 64 were females and 28 were males. Overall, 11 morphometric characteristics were measured. Carapace length of sampled individuals ranged from 48.46 to 76.09 mm, and body weight from 47.06 to 221.39 g. The length–weight relationship showed negative allometry for males and isometric growth for females. Analysis of the stomach content revealed the crab’s preference for crustaceans (20.28%) and cephalopods (10.58%), less for fish (3.4%) and shellfish (0.28%). Size at first sexual maturity (CL50%) of 59.25 and 66.92 mm was estimated for males and females, respectively. Epibiotic serpulid polychaetes were recorded on the crab exoskeleton with an overall prevalence of 29.3%. Analyses of a partial sequence of mtCOI showed high haplotype (Hd = 0.964) and low nucleotide diversity (π = 0.00598). Phylogenetic inference and estimation of population differentiation (FST = 0.013, p = 0.271) with publicly available Mediterranean sequences currently imply one homogenous population unit. To the best of our knowledge, these are the first nucleotide sequences of C. granulata from the Adriatic Sea made publicly available.

Bioinspired Chiral Template Guided Mineralization for Biophotonic Structural Materials.

Nature provides numerous biomineral design inspirations for constructing structural materials with desired functionalities. However, large-scale production of damage-tolerant Bouligand structural materials with biologically comparable photonics remains a longstanding challenge. Here, an efficient and scalable artificial molting strategy, based on self-assembly of cellulose nanocrystals and subsequent mineralization of amorphous calcium carbonate, is developed to produce biomimetic materials with an exceptional combination of mechanical and photonic properties that are usually mutually exclusive in synthetic materials. These biomimetic composites exhibit tunable mechanics from "strong and flexible", whichexceeds the benchmark of natural chiral materials, to "stiff and hard", which is comparable to natural and synthetic counterparts. Especially, the biomimetic composites possess ultrahigh stiffness of 2GPa in their fully water-swollen state-a value well beyond hydrated crab exoskeleton, cartilage, tendon, and stiffest synthetic hydrogels, combined with exceptional strength and resilience. Additionally, these composites are distinguished by the tunable chiral structural color and water-triggered switchable photonics that are absent in most artificial mineralized materials, as well as unique hydroplastic properties. This study opens the door for a scalable synthesis of resilient biophotonic structural materials in practical bulk form.

Exceptional properties of hyper-resistant armor of a hydrothermal vent crab

Animals living in extreme environments, such as hydrothermal vents, would be expected to have evolved protective shells or exoskeletons to maintain homeostasis. The outer part of the exoskeleton of vent crabs (Austinograea sp.) in the Indian Ocean hydrothermal vent was one of the hardest (approximately 7 GPa) biological materials ever reported. To explore the exoskeletal characteristics of vent crabs which enable them to adapt to severe environments, a comparative analysis was conducted with the Asian paddle crab (Charybdis japonica) living in coastal areas. Nanoindentation, thermogravimetric analysis, scanning electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy were used to analyze the mechanical properties, thermal stability, structure, surface components, and the composition of compounds, respectively. Though both species have four-layered exoskeletons, the outermost layer of the vent crab, a nano-granular structure, was much thicker than that of the coastal crab. The proportions of aluminum and sulfur that constitute the epicuticle of the exoskeleton were higher in the vent crab than in the coastal crab. There was a lack of water or volatile substances, lots of CaCO3, and no carotenoid-based compounds in the exoskeleton of the vent crab. These might have improved the mechanical properties and thermal stability of the hydrothermal species.

Chitosan and Chitooligosaccharide: The Promising Non-Plant-Derived Prebiotics with Multiple Biological Activities.

Biodegradable chitin is the second-most abundant natural polysaccharide, widely existing in the exoskeletons of crabs, shrimps, insects, and the cell walls of fungi. Chitosan and chitooligosaccharide (COS, also named chitosan oligosaccharide) are the two most important deacetylated derivatives of chitin. Compared with chitin, chitosan and COS not only have more satisfactory physicochemical properties but also exhibit additional biological activities, which cause them to be widely applied in the fields of food, medicine, and agriculture. Additionally, due to their significant ability to improve gut microbiota, chitosan and COS are deemed prospective prebiotics. Here, we introduced the production, physicochemical properties, applications, and pharmacokinetic characteristics of chitosan and COS. Furthermore, we summarized the latest research on their antioxidant, anti-inflammatory, and antimicrobial activities. Research progress on the prebiotic functions of chitosan and COS is particularly reviewed. We creatively analyzed and discussed the mechanisms and correlations underlying these activities of chitosan and COS and their physicochemical properties. Our work enriched people’s understanding of these non-plant-derived prebiotics. Based on this review, the future directions of research on chitosan and COS are explored. Collectively, optimizing the production technology of chitin derivatives and enriching understanding of their biological functions will shed more light on their capability to improve human health.

An Ultra‐Strong, Water Stable and Antimicrobial Chitosan Film with Interdigitated Bouligand Structure

AbstractNatural polymeric materials are an attractive potential replacement for non‐biodegradable plastics. However, one of the main challenges for high‐end applications of these materials, is to maintain their high mechanical properties in a watery environment. Here, inspired by the reinforcement principle of multiscale architecture in natural crab exoskeletons, an ultra‐strong and hydrostable film is developed through a top‐down method directly from the crab shell. The resulting chitosan film exhibits an outstanding isotropic tensile strength of ≈220 MPa and a superior wet strength of ≈70 MPa, which is significantly higher than that of conventional polysaccharide‐based materials and many commercially used plastics. Its excellent mechanical properties are due to the realization of strong interactions between chitosan fibrils even in wet conditions through interdigitation and densification processes without other additives. Additionally, it also possesses outstanding transparency, flexibility, antimicrobial ability, and biodegradability, making it a promising high‐performance and eco‐friendly material for many potential applications.

Crab (Charybdis natator) exoskeleton derived chitosan nanoparticles for the in vivo delivery of poorly water-soluble drug: Ibuprofen

The study aims to extract and purify chitosan (CS) from the exoskeleton of crab (C. natator) and develop ibuprofen (IBU) encapsulated CS nanoparticles (IBU-CSNPs). Analysis of purified CS revealed characteristic functional and crystallinity peaks. Moreover, morphological analysis of prepared IBU-CSNPs showed uniform spherical shape with a size range of 40–100 nm whereas encapsulation efficiency (EE%) and loading capacity (LC%) were estimated to be 68.94 ± 1.61% and 28 ± 1.18% respectively. Further, in vitro release profile of IBU from IBU-CSNPs was observed to be in biphasic form with initial release up to 15 h followed by the sustained release in different test conditions. Further, the effects of purified CS on the viability of RAW264.7 cells exhibited no toxic effects in higher concentrations. Furthermore, fluorescein isothiocyanate (FITC) conjugated nanoparticles (FITC-IBU-CSNPs) were investigated on in vivo model of adult zebrafish for time-dependent circulation and accumulation of the drug through the nano-carrier system. It was observed that the drug diffusion from the nanoparticles was in a sustained manner throughout the gastrointestinal region which resulted in suppression of inflammation. Overall, this study provides an effective and facile process for preparing a crab CS-based nano-carrier system used for the delivery of IBU in vivo which may help in the curing of prolonged chronic inflammatory diseases. Moreover, it may also help to reduce adverse effects of these drugs in the gastrointestinal tract such as ulcers and bleeding.

Crushing behavior and energy absorption of a bio-inspired bi-directional corrugated lattice under quasi-static compression load

The dactyls of Odontodactylus scyllarus have been proved to be an exceptionally damage-tolerant natural material that can readily smash mollusk shells, crab exoskeletons or other hard-shelled preys. In the present study, inspired by the microstructural features of the impact region in the dactyl of Odontodactylus scyllarus, a novel lightweight bi-directionally corrugated lattice was designed and manufactured by additive manufacturing technology to enhance impact energy absorption capacity. The quasi-static compressive properties and energy absorption behavior of the bi-directionally corrugated lattices were investigated experimentally. The compression responses were simulated by finite element (FE) models to duplicate the deformation process. A parametric analysis based on the validated FE model was conducted to study the effects of wave number, wave amplitude and relative density on collapse mode and energy absorption characteristic of the corrugated lattice structures. The collapse process of the bi-directional corrugated lattices can be mainly classified into three representative failure modes, including the full-folded mode, the global buckling mode and the transitional mode. It was found that the specific energy absorption of the corrugated lattice has a strong connection with the three representative collapse modes. With the same relative density, the lattices collapsed with a transitional mode have better energy absorption than those collapsed with a global buckling mode. Due to the higher energy absorption capacity and crushing force efficiency, the corrugated structures collapsed with a transitional mode are more efficient and suitable to act as an energy absorber than those collapsed with the other collapse modes.

Use of Plant Growth Promoting Rhizobacteria in Combination with Chitosan on Maize Crop: Promising Prospects for Sustainable, Environmentally Friendly Agriculture and against Abiotic Stress

Faced with the problems posed by the abusive use of chemical fertilizers and pesticides, it is important to find other alternatives that can guarantee a sustainable and environmentally friendly agriculture. The objective of this study was to evaluate the tolerance of a PGPR (plant growth promoting rhizobacteria) Pseudomonas putida strain to different abiotic stress in in vitro conditions and the synergistic effect of this rhizobacterium in combination with chitosan extracted from crab exoskeletons on the growth of maize in greenhouse conditions. The strain of P. putida was put in culture at different temperatures, pH, and NaCl concentrations to determine its growth. Then, this strain in combination with chitosan extracts were tested for their ability to improve maize growth for 30 days. The results showed that the P. putida strain showed excellent resistance capacities to different salt concentrations, pH, and temperature variations. Moreover, an improvement in plant growth and biomass yield parameters was observed. The highest values of height, diameter, and leaf area were obtained with the plants treated with the combination of chitosan extracted from Cardisoma armatum and P. putida, with increases of 26.8%, 31%, and 55.7%, respectively, compared to the control. This study shows the possibility of using chitosan and rhizobacteria as biostimulants to improve productivity and increase maize yield in a sustainable manner.

Is it Possible to Keep the Exoskeleton of the Crab Callinectes Ornatus Soft for Several Days?

Soft-shell crab is considered a gastronomic delicacy, reaching high values in the international market. Under normal conditions, the process of hardening of the crab's exoskeleton after moulting takes approximately two days to complete; however, the commercial consistency of soft-shell crab is lost in just 3 hours. The goal of this research was to evaluate the effects of chemical changes of water on the duration of postmoult, specifically at the stage in which they can be marketed as soft-shelled crab. In this research, Callinectes ornatus (n=241) underwent two experiments: One group was maintained in tanks with partial daily water renewal (Experiment 1), and other in tanks without water renewal (Experiment 2). In the experiment 1, the chemical characteristics of the water remained unchanged over time (p > 0.05), and the median time to hardening of the exoskeleton after moulting was 3 hours.