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Chitin and its derivative chitosan are popular constituents in wound-treatment technologies due to their nanoscale fibrous morphology and attractive biomedical properties that accelerate healing and reduce scarring. These abundant natural polymers found in arthropod exoskeletons and fungal cell walls affect almost every phase of the healing process, acting as hemostatic and antibacterial agents that also support cell proliferation and attachment. However, key differences exist in the structure, properties, processing, and associated polymers of fungal and arthropod chitin, affecting their respective application to wound treatment. High purity crustacean-derived chitin and chitosan have been widely investigated for wound-treatment applications, with research incorporating chemically modified chitosan derivatives and advanced nanocomposite dressings utilizing biocompatible additives, such as natural polysaccharides, mineral clays, and metal nanoparticles used to achieve excellent mechanical and biomedical properties. Conversely, fungi-derived chitin is covalently decorated with -glucan and has received less research interest despite its mass production potential, simple extraction process, variations in chitin and associated polymer content, and the established healing properties of fungal exopolysaccharides. This review investigates the proven biomedical properties of both fungal- and crustacean-derived chitin and chitosan, their healing mechanisms, and their potential to advance modern wound-treatment methods through further research and practical application.

Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throughout the Portuguese coast by purse seine vessels as bycatch. After standard chitin extraction procedures, water-soluble chitosan products were obtained via two different methods: (1) N-acetylation with the addition of acetic anhydride and (2) a reaction with hydrogen peroxide. The chemical structure and molecular weight of chitosan derivatives, water-soluble chitosan (WSC) and chitooligosaccharides (COS), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and gel permeation chromatography (GPC). Antioxidant and metal chelation activities were evaluated, and the growth inhibition capacity was tested on four phytopatogens. The chitooligosaccharides from pereopods (pCOS) and shell body parts (sCOS) inhibited all fungal species tested, particularly Cryphonectria parasitica with 84.7% and 85.5%, respectively. Both radical scavenging and antifungal activities proved to be dose-dependent. Chitooligosaccharides with a low molecular weight (2.7, 7.4, and 10.4 Kg·mol−1) showed the highest activity among all properties tested. These results suggested that chitosan derivatives from P. henslowii raw material could potentially be used against phytopathogens or as ingredient in cosmetics and other products related to oxidative stress.

Paralytic shellfish poisoning (PSP) is a pervasive human health concern associated with subsistence, recreationally and commercially harvested Alaskan shellfish. PSP is caused by saxitoxins (STX), a family of structurally similar neurotoxins produced by the marine microalgae Alexandrium catenella (formerly A. fundyense ). These toxins accumulate in filter-feeding shellfish such as clams, mussels and oysters. While PSP is commonly associated with consuming bivalves, toxic STX levels can also be found in crab viscera (crab butter). The first cases of PSP from consuming Dungeness crab viscera ( Metacarcinus magister ) were reported in 1992. Although this incident and others did not involve commercially harvested crab, they did impact management of the Dungeness crab fishery in Alaska. Current regulations in southeast Alaska permit the sale of whole Dungeness crab, whereas those in the Kodiak Archipelago must have their viscera removed post-harvest to prevent PSP. This study examines the impacts of STXs and current regulations on the Alaskan crab fishery, with a focus on Dungeness crab. Data on commercial landings and the value of harvested Dungeness crab and processed products showed that regulations to protect human health, combined with market forces over the past 30 years, have shifted the fishery’s focus toward Dungeness crab products without viscera. The study also presents time series data on STX concentrations in Dungeness crab from 1992 to 2023, along with maps indicating collection locations and their associated toxicity levels. The same data for King crab ( Paralithodes or Lithodes spp.) and Tanner (Snow) crab ( Chionoecetes spp.) are included to assess the prevalence of STX in these commercially harvested species. Further, a preliminary analysis suggests regional variations in the toxicity of A. catenella strains could affect regional shellfish toxicity.

Of recent, immense attention has been given to chitosan in the biomedical field due to its valuable biochemical and physiological properties. Traditionally, the chief source of chitosan is chitin from crab and shrimp shells. Chitin is also an important component of fish scales, insects and fungal cell walls. Thus, the aim of this study was to isolate and characterize chitosan from locally available material for potential use in the biomedical field. Chitosan ash and nitrogen contents ranged from 1.55 to 3.5% and 6.6 to 7.0% respectively. Molecular weight varied from 291 to 348KDa. FTIR spectra revealed high degree of similarity between locally isolated chitosan and commercial chitosan with DD ranging from 77.8 to 79.1%. XRD patterns exhibited peaks at 2θ values of 19.5° for both mushroom and banana weevil chitosan while Nile perch scales chitosan registered 3 peaks at 2θ angles of 12.3°, 20.1° and 21.3° comparable to the established commercial chitosan XRD pattern. Locally isolated chitosan exhibited antimicrobial activity at a very high concentration. Ash content, moisture content, DD, FTIR spectra and XRD patterns revealed that chitosan isolated from locally available materials has physiochemical properties comparable to conventional chitosan and therefore it can be used in the biomedical field.

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (Mw) of 6–21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan’s origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.

The cycling and fate of polycyclic aromatic hydrocarbons (PAHs) is not well understood in estuarine systems. It is critical now more than ever given the increased ecosystem pressures on these critical coastal habitats. A budget of PAHs and cycling has been created for Galveston Bay (Texas) in the northwestern Gulf of Mexico, an estuary surrounded by 30–50% of the US capacity of oil refineries and chemical industry. We estimate that approximately 3 to 4 mt per year of pyrogenic PAHs are introduced to Galveston Bay via gaseous exchange from the atmosphere (ca. 2 mt/year) in addition to numerous spills of petrogenic PAHs from oil and gas operations (ca. 1.0 to 1.9 mt/year). PAHs are cycled through and stored in the biota, and ca. 20 to 30% of the total (0.8 to 1.5 mt per year) are estimated to be buried in the sediments. Oysters concentrate PAHs to levels above their surroundings (water and sediments) and contain substantially greater concentrations than other fish catch (shrimp, blue crabs and fin fish). Smaller organisms (infaunal invertebrates, phytoplankton and zooplankton) might also retain a significant fraction of the total, but direct evidence for this is lacking. The amount of PAHs delivered to humans in seafood, based on reported landings, is trivially small compared to the total inputs, sediment accumulation and other possible fates (metabolic remineralization, export in tides, etc.), which remain poorly known. The generally higher concentrations in biota from Galveston Bay compared to other coastal habitats can be attributed to both intermittent spills of gas and oil and the bay's close proximity to high production of pyrogenic PAHs within the urban industrial complex of the city of Houston as well as periodic flood events that transport PAHs from land surfaces to the Bay.

Many factors affect the flavor of crabs. However, impact of temperature on flavor has not been reported. Here, we examined Scylla paramamosain collected within the main four producing areas in China from north sampling point (NP) and south sampling point (SP), respectively. The contents of flavouring-related substances in hepatopancreas, muscles and gonads were determined by high-performance liquid chromatography (HPLC). Meanwhile, high-throughput sequencing of 16S RNA gene was used to reveal the diversity distribution of gut microbiota at each sample collection point. Comparisons among flavor substances of edible parts, the implied higher temperature in SP may be beneficial to the accumulation of flavor substances in gonads, while lower temperature in NP may be beneficial to the accumulation of flavor substances in muscles and hepatopancreas. The gut microbiota of crabs, was analyzed via 16S rRNA gene sequencing. The results of gut microbiota showed that there were significant differences in the distribution of gut microbiota in NP and SP. The microbiota composition of SP has a high distribution richness and no absolute dominant bacteria, while NP has absolute dominant bacteria and its microbiota richness was lower than SP. The results of redundancy analysis (RDA) showed that there was a significant correlation between temperature and the relative abundance of gut microbiota, and a significant correlation between gut microbiota and the content of flavor substances. This study indicates that temperature may be one of the main factors for the differences of flavor substances between SP and NP, which was most probably mediated by gut microbiota. Further exploration is needed with laboratory experiments in which the environment is more precisely controlled if these views are to be determined.

In this study, a method for the determination of eight biogenic amines (BAs), including tyramine (Tyr), 2-phenylethylamine (2-Phe), histamine (His), tryptamine (Trp), spermidine (Spd), spermine (Spm), cadaverine (Cad), and putrescine (Put), in crab was established using ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS), using a magnetic solid-phase extraction (MSPE) pretreatment, without derivatization, and the content changes in regard to these eight biogenic amines in the traditional Chinese dish, pickled swimming crabs, were investigated. The samples were purified via MSPE, using C nanofiber-coated magnetic nanoparticles (Fe3O4@C-NFs) as sorbents. The experimental variables involved in the MSPE, including the solution pH, adsorption and desorption time, adsorbent usage, and type and volume of the eluent, were investigated and optimized. Method validation indicated that the developed method showed good linearity (R2 > 0.995); the average recovery rates were 84.7% to 115%, with the intra-day and inter-day relative standard deviations (RSD, n = 6) ranging from 3.7% to 7.5% and 4.2% to 7.7%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for the eight BAs were 0.1 mg/kg~1.0 mg/kg and 0.3 mg/kg~3.0 mg/kg, respectively. Finally, this method was applied to determine the changes in the eight biogenic amines in pickled swimming crabs (Portunus trituberculatus) during storage at 20 °C and 400 BAC. Among the BAs evaluated, Cad, Put, and Tyr were the predominant amines formed during storage. The final content of Cad, Put, and Tyr reached 22.9, 20.1, and 29.0 mg/100 g at 4 °C for 16 d, and 47.1, 52.3, and 72.0 mg/100 g at 20 °C for 96 h, respectively. The results from this study can be used to expand the application range of magnetic materials in biogenic amine pretreatment and to strengthen the quality control of the traditional Chinese dish, pickled swimming crabs.

With the development of the aquatic products processing industry, 6–8 million tons of shrimp and crab shell waste are produced globally annually, but, due to the lack of high-value conversion technology, crab shells are often discarded in large quantities as a by-product of processing. Pseudomonas-based microbial cell factories are capable of biosynthesis of high-value products using a wide range of substrates; however, there is currently no reliable fermentation model for producing high-value chemicals using crab shell waste by Pseudomonas strains. In this study, we first explored the culture conditions of shell fermentation using KT2440 through single-factor and orthogonal experiments, and the optimized fermentation parameters obtained are given as follows: a temperature of 30 °C, fermentation time of 42 h, substrate solid–liquid ratio of 7%, and rotational speed of 200 rpm. After optimization, the maximum cell growth was increased by 64.39% from 350.67 × 108 CFU/mL to 576.44 × 108 CFU/mL. Combined with engineering modification, two engineered strains, KT+IV and KT+lasBT, expressing exogenous proteases, were obtained, and the maximum growth was increased from 316.44 × 108 CFU/mL to 1268.44 × 108 CFU/mL and 616.89 × 108 CFU/mL, which were 300.84% and 94.94% higher, respectively. In addition, the engineered strain KT+NtrcT-D55E, which regulates nitrogen metabolism, was obtained, and the accumulation of intracellular polyhydroxy fatty acid esters (PHA) was increased from 20.00 mg/L to 78.58 mg/L, which was a significant increase of 292.93% relative to the control group. This study provides a theoretical basis and technical support for the high-value utilization of shrimp and crab shell resources and the development of environmentally friendly bioproducts.

When a range-shifting species colonizes an ecosystem it has not previously inhabited, it may experience suboptimal conditions that challenge its continued persistence and expansion. Some impacts may be partially mitigated by artificial habitat analogues: artificial habitats that more closely resemble a species’ historic ecosystem than the surrounding habitat. If conditions provided by such habitats increase reproductive success, they could be vital to the expansion and persistence of range-shifting species. We investigated the reproduction of the mangrove tree crab Aratus pisonii in its historic mangrove habitat, the suboptimal colonized salt marsh ecosystem, and on docks within the marsh, an artificial mangrove analogue. Crabs were assessed for offspring production and quality, as well as measures of maternal investment and egg quality. Aratus pisonii found on docks produced more eggs, more eggs per unit energy investment, and higher quality larvae than conspecifics in the surrounding salt marsh. Yet, crabs in the mangrove produced the highest quality larvae. Egg lipids suggest these different reproductive outcomes result from disparities in the quality of diet-driven maternal investments, particularly key fatty acids. This study suggests habitat analogues may increase the reproductive fitness of range-shifting species allowing more rapid expansion into, and better persistence in, colonized ecosystems.