Shell Chitin Research Articles

Using stable isotope chronologies within squid gladii (Doryteuthis gahi) to evaluate dietary differences by fishing region and season

Stable isotopes are a useful tool for understanding diet and migration in squid, which often play an important role in marine food webs. The Patagonian long-finned squid fishery around Falkland Islands waters is managed separately for each of its biannual fishing seasons and 2 sub-areas of the fishing zone. However, factors driving differences in the timing of recruitment and squid size between sub-areas have never been resolved. To investigate whether seasonal and spatial variation in life history parameters of the Patagonian long-finned squidDoryteuthis gahiis driven by differences in diet, stable isotope profiles (δ13C and δ15N) were measured along the gladius—the internal chitinous shell—to reconstruct a chronological record of habitat and feeding variations and to compare fishing seasons and sub-areas using a mixed modelling approach. Here we show that isotopic niche was distinct between the fishing seasons, but negligible differences in isotopic niche were found between sub-areas of the fishing zone. This suggests that spatial differences in life history parameters are not a result of dietary variation. Substantial variation in δ13C and δ15N values along the gladius indicated versatility in feeding behaviours and dietary habits over time. Squid in the second fishing season occupied a lower trophic level (mean = 3.2) than the first season (mean = 3.5). Patterns in δ13C values indicated more complex and substantial migration patterns in the second fishing season. This coincides with the current knowledge of this species’ spawning migrations. We anticipate that these data may be used for future studies investigating the role of squid within the Patagonian Shelf marine ecosystem. Analysis of the squid gladius has applications for other loliginid squid species in future studies.

Novel Bi-Modular GH19 Chitinase with Broad pH Stability from a Fibrolytic Intestinal Symbiont of Eisenia fetida, Cellulosimicrobium funkei HY-13.

Endo-type chitinase is the principal enzyme involved in the breakdown of N-acetyl-d-glucosamine-based oligomeric and polymeric materials through hydrolysis. The gene (966-bp) encoding a novel endo-type chitinase (ChiJ), which is comprised of an N-terminal chitin-binding domain type 3 and a C-terminal catalytic glycoside hydrolase family 19 domain, was identified from a fibrolytic intestinal symbiont of the earthworm Eisenia fetida, Cellulosimicrobium funkei HY-13. The highest endochitinase activity of the recombinant enzyme (rChiJ: 30.0 kDa) toward colloidal shrimp shell chitin was found at pH 5.5 and 55 °C and was considerably stable in a wide pH range (3.5–11.0). The enzyme exhibited the highest biocatalytic activity (338.8 U/mg) toward ethylene glycol chitin, preferentially degrading chitin polymers in the following order: ethylene glycol chitin > colloidal shrimp shell chitin > colloidal crab shell chitin. The enzymatic hydrolysis of N-acetyl-β-d-chitooligosaccharides with a degree of polymerization from two to six and colloidal shrimp shell chitin yielded primarily N,N′-diacetyl-β-d-chitobiose together with a small amount of N-acetyl-d-glucosamine. The high chitin-degrading ability of inverting rChiJ with broad pH stability suggests that it can be exploited as a suitable biocatalyst for the preparation of N,N′-diacetyl-β-d-chitobiose, which has been shown to alleviate metabolic dysfunction associated with type 2 diabetes.

The C2 entity of chitosugars is crucial in molecular selectivity of the Vibrio campbellii chitoporin

The marine bacterium Vibrio campbellii expresses a chitooligosaccharide-specific outer-membrane channel (chitoporin) for the efficient uptake of nutritional chitosugars that are externally produced through enzymic degradation of environmental host shell chitin. However, the principles behind the distinct substrate selectivity of chitoporins are unclear. Here, we employed black lipid membrane (BLM) electrophysiology, which handles the measurement of the flow of ionic current through porins in phospholipid bilayers for the assessment of porin conductivities, to investigate the pH dependency of chitosugar–chitoporin interactions for the bacterium’s natural substrate chitohexaose and its deacetylated form, chitosan hexaose. We show that efficient passage of the N-acetylated chitohexaose through the chitoporin is facilitated by its strong affinity for the pore. In contrast, the deacetylated chitosan hexaose is impermeant; however, protonation of the C2 amino entities of chitosan hexaose allows it to be pulled through the channel in the presence of a transmembrane electric field. We concluded from this the crucial role of C2-substitution as the determining factor for chitoporin entry. A change from N-acetylamino- to amino-substitution effectively abolished the ability of approaching molecules to enter the chitoporin, with deacetylation leading to loss of the distinctive structural features of nanopore opening and pore access of chitosugars. These findings provide further understanding of the multistep pathway of chitin utilization by marine Vibrio bacteria and may guide the development of solid-state or genetically engineered biological nanopores for relevant technological applications.

Association of the alga Cladogonium sp. with a multifactorial disease outbreak in dwarf shrimp (Neocaridina davidi).

This study outlines a multifactorial disease outbreak in a population of the freshwater shrimp Neocaridina davidi, with the focus on a rarely described parasitic alga. Within this multifactorial disease outbreak, low but consistent mortality was observed. During microscopic examination, an infection of the shrimp with bacterial and fungal-like agents was diagnosed. Furthermore, the green alga Cladogonium sp. was found in pleopodal regions. The alga compromised the body surface of the shrimp, and its rhizoids penetrated the chitin shell and reached into the subcutaneous tissue. This might be a first indication of a parasitic lifestyle. In addition to a morphological description, sequencing data are presented which allow the taxonomic classification of the organism within the order Trentepohliales.

Evaluation of the ability of cholera vibrios to form a biofilm on the surface of the chitinous shell of a crayfish by real-time PCR

Introduction. Most of the bacteria exist in natural ecosystems not in the form of free floating cells; but in the form of biofilms attached to the substrate. One of the most ecologically important substrates is chitin. Vibrio cholerae; like most members of the Vibrionaceae family; has a chitinolytic complex and can degrade chitin. The ability of V. cholerae to form a biofilm on chitinous substrates can explain the mechanism of the formation of an ecological niche for the preservation and transfer of the pathogen to new regions with the likelihood of the formation of new foci of cholera.Aim — to determine the ability of V. cholerae to form a biofilm on the chitinous shell of crayfish (Astacus astacus) by means of real-time PCR.Materials and methods. A comparative analysis of the timing of biofilm formation by V. cholerae of different serogroups and toxigenicity was carried out.Results. In the course of the study; it was found that cholera vibrios were shown to be capable of forming a biofilm regardless the serogroup and toxigenicity. However; toxigenic tcpA+ strains have a higher intensity of biofilm formation than nontoxigenic ones; in which the tcpA gene is absent.

Increasing efficiency of the homogenization process for production of chitin nanofibers for barrier film applications

Chitin nanofibers (ChNFs) are of interest for barrier materials but are often extracted by high pressure homogenization (HPH) with high energy utilization. We studied the influence of deacetylation (DA) and pressure on HPH of shrimp chitin and the resulting solution cast films. Deacetylation to 72% DA resulted in improved ChNF suspension and film light transmission, strain at break, and tensile strength compared to chitin with DA of 89%. The oxygen permeability (OP) of the films was not affected by the modification and remained at low values of 1.9–2.4 cm3 μm/m2/day/kPa. We also show that deacetylation enables HPH intensity to be reduced during extraction of ChNFs from crab shell chitin (63% lower pressure and 73% reduction in number of passes), while achieving a low OP. Deacetylation pretreatment reduces HPH process intensity required to achieve oxygen barrier properties in ChNF films.

Adsorptive kinetics, isotherm and thermodynamic analysis of fishpond effluent coagulation using chitin derived coagulant from waste Brachyura shell

High grade chitin extracted from Brachyura shell waste was successfully used for adsorptive de-colorization of highly turbid fishpond effluent. Brachyura shell chitin was characterized via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results obtained from the characterization indicated that the extracted chitin possessed significant features required for surface phenomenon driven matrices. The best efficiency obtained for turbidity and color removal were 88% and 91%, respectively, at BSC dosage of 1.8 g/L, pH of 6.0 and temperature of 45°C. The maximum adsorption capacity of the de-colorization process onto BSC was found to be 265.59 mg/g. Results from kinetic analysis suggested that pseudo-second order model was most accurate (R2 > 0.99) in predicting the experimental data. Webber-Morris intraparticle diffusion rate constant (Kipd) demonstrated that the adsorptive process depended more on film diffusion mechanism. Equilibrium study was carried out using Langmuir, Freundlich, Temkin, Dubinin Radushkevich and Brunauer-Emmett-Teller isotherm model at 30, 40 and 50°C. Fitness appraisal analysis of the isotherm models pointed out that experimental data aligned significantly with Langmuir and Temkin isotherm (R2 > 0.94), suggesting the homogenous and monolayer mode of the adsorptive process. Values of Gibbs free energy (− ΔG0= 1.7816 – 2.6706 kJ /mol), enthalpy (ΔH0= 11.6867kJ/ mol), activation energy (EA= 13.2330kJ/ mol) and entropy (ΔS0= 44.4511J / molK) obtained from thermodynamic analysis confirmed the spontaneous, endothermic, favorable and physical nature of the process.

Key parameters optimization of chitosan production from Aspergillus terreus using apple waste extract as sole carbon source.

Chitosan is commonly obtained from shrimp and crab shell chitin by deacetylation; however, such supplies appear limitation. An alternative source of chitosan is cell wall in certain fungi. In this study, chitosan production through submerged fermentation of Aspergillus terreus on apple waste extract as sole carbon source was investigated. Monod equation with a maximum specific growth rate of 0.083h-1 and half-saturation constant of 6.67 w/v% was best described the kinetic of growth. Results of response surface methodology showed the highest chitosan to substrate yield of 49.32mg gsubstrate-1, chitosan to fungal biomass yield of 140.9mg gcell-1, and fungal biomass to substrate yield of 0.387 gcell gsubstrate-1 were simultaneously obtained at temperature 30.0°C, initial pH 5.98, and ammonium nitrate concentration 5.0g L-1. The chitosan produced at the optimum condition was characterized by FTIR, TGA, and DSC analysis, and degree of deacetylation was 88.2%.

Characterization of Novel Chitin-degrading laceyella spp. Strains from New Athos Cave (Abkhazia) Producing Thermostable Chitinases

Nine chitin-degrading isolates of moderately thermophilic bacteria with temperature optimum for growth and chitin destruction at 50–55°C were isolated from soils of the New Athos Cave (Abkhazia). Four most active bacterial cultures with chitinase production yields 0.11–0.28 U mL–1 (at 48°C) were screened from seven isolates forming aerial mycelium. Selected isolates were identified as Laceyella sp. species based on their cultural, morphological, physiological, and biochemical characteristics, as well as on phylogenetic analysis of their 16S rRNA gene sequences; these formed a cluster with L. sacchari, L. sediminis, and L. tengchongensis on the phylogenetic tree with sequence identity of 96.43–97.21%. Occurrence of isolated thermoactinomycetes in the cave was confined to tour circuit zones and the area inundated with flood waters. Laceyella spp. strains NAC-16-5 A-4 and NAC-16-5 A-5 degraded 85–100% of colloidal chitin (5 g L–1) after 96 h of submerged cultivation (48°C). Inducible synthesis of chitinolytic enzymes was observed in all selected strains and reached its maximum in the presence of crab shell chitin. The enzymatic complex of Laceyella sp. NAC-16-5 A-4 was active in pH range 4–10.5 with two optima at pH 5.5 and 7.0. While crude chitinases of all studied strains exhibited maximal activity at 60–70°C with similar temperature optima (65°C), the enzyme complexes from strains NAC-16-5 A-2 and NAC-16-5 A-4 were most stable at 70°C.

Species-Specific Quorum Sensing Represses the Chitobiose Utilization Locus in Vibrio cholerae.

The marine facultative pathogen Vibrio cholerae forms complex multicellular communities on the chitinous shells of crustacean zooplankton in its aquatic reservoir. V. cholerae-chitin interactions are critical for the growth, evolution, and waterborne transmission of cholera. This is due, in part, to chitin-induced changes in gene expression in this pathogen. Here, we sought to identify factors that influence chitin-induced expression of one locus, the chitobiose utilization operon (chb), which is required for the uptake and catabolism of the chitin disaccharide. Through a series of genetic screens, we identified that the master regulator of quorum sensing, HapR, is a direct repressor of the chb operon. We also found that the levels of HapR in V. cholerae are regulated by the ClpAP protease. Furthermore, we show that the canonical quorum sensing cascade in V. cholerae regulates chb expression in an HapR-dependent manner. Through this analysis, we found that signaling via the species-specific autoinducer CAI-1, but not the interspecies autoinducer AI-2, influences chb expression. This phenomenon of species-specific regulation may enhance the fitness of this pathogen in its environmental niche.IMPORTANCE In nature, bacteria live in multicellular and multispecies communities. Microbial species can sense the density and composition of their community through chemical cues using a process called quorum sensing (QS). The marine pathogen Vibrio cholerae is found in communities on the chitinous shells of crustaceans in its aquatic reservoir. V. cholerae interactions with chitin are critical for the survival, evolution, and waterborne transmission of this pathogen. Here, we show that V. cholerae uses QS to regulate the expression of one locus required for V. cholerae-chitin interactions.

Chitinase-E from Chitiniphilus shinanonensis generates chitobiose from chitin flakes

Enzymatic deconstruction of chitin to chitobiose is of significant interest in view of its various biological applications. Here we report detailed insights into the chitin degradation by chitinase-E from a chitinolytic bacterium Chitiniphilus shinanonensis (CsChiE). CsChiE was optimally active at 50 °C in 50 mM sodium phosphate pH-7.0. It showed a kcat and overall catalytic efficiency (Kcat/Km) as 3.9 × 103 s−1 and 0.6 × 103 s−1 mg−1 mL, respectively, on colloidal chitin (CC). CsChiE efficiently hydrolyzed crystalline polymers like α-, β- and CC and released chitobiose as the predominant product (11.3 mM on CC). Further, CsChiE displayed substantial activity towards the unmilled crab shell chitin waste (chitin-flakes) and generated chitobiose. Activity studies on chitooligosaccharides revealed that CsChiE produced chitobiose as the major product. Our results indicate that the multi-modular CsChiE is a non-processive exo-chitinase which is more suitable to generate chitobiose from a variety of chitinous substrates including unprocessed chitin-flakes.

Factorial Design for Optimizing and Modeling the Removal of Organic Pollutants from Olive Mill Wastewater Using a Novel Low-Cost Bioadsorbent

Low-cost bioadsorbent such as shrimp shell chitin was used for the removal of polyphenols and COD from olive mill wastewater (OMW). In order to achieve a high polyphenols and chemical oxygen demand (COD) removal efficiency and to reduce the number of experiments, two levels of fractional 24 factorial design experiments were carried out. The influence of different experimental parameters such as solution pH, adsorbent concentration, contact time, stirring speed, and their interactions during polyphenols and COD removal were investigated. Optimized values of pH, adsorbent concentration, contact time, and stirring speed were found equal to 12, 10 g/L, 24 h, and 420 rpm/min, respectively. The maximum polyphenol uptake under these experimental conditions reached 69.47%. Whereas the maximum removal of COD achieve 43% in 10 g/L, 12, 24 h, and 80 rpm/min for adsorbent concentration, pH, contact time, and stirring speed as optimal conditions, respectively. The experimental equilibrium data were tested using the Freundlich and Langmuir isotherm models. It was found that adsorption of polyphenols on shrimp shell chitin is well fitted both models. Kinetics of the adsorption process was studied by investigating the pseudo-first-order, pseudo-second-order kinetics, and intraparticle diffusion mechanism and showed that the pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model and intraparticle diffusion. These results revealed that shrimp shell chitin can be used as an effective and low-cost adsorbent to remove polyphenols and COD from OMW.

Enzymatic conversion and recovery of protein, chitin, and astaxanthin from shrimp shell waste

Accumulated shrimp shell waste is a source of environmental pollution and represents a waste of resources. Recycling shell waste into valuable fractions using cost-effective and environmentally benign approaches remains challenging. To address this issue, in this study a clean and efficient enzymatic process was developed to recover most components of shrimp shell waste including protein, chitin, astaxanthin, and minerals. The process used two recombinant aspartic proteases for protein hydrolysis, recombinant chitinase for chitin hydrolysis, and ethyl acetate for astaxanthin extraction. Deproteinization rendered shell chitin accessible to chitinase, and astaxanthin was easily extracted from shell residue after protein and chitin removal. The process was completed within hours and resulted in high recovery rates of protein (91.4%) and chitin (88.9%). Importantly, amino acids in peptides, the N-acetyl group of chitin oligomers, and astaxanthin in the final products were preserved in their natural states, unlike with traditional chemical or physical treatments. The products have potential applications in nutrition and as anti-inflammatory and antioxidant agents. This enzymatic process promotes sustainable development by establishing a circular economy in shrimp processing, thus offering both economic and environmental benefits.

Enhanced glucosamine production through synergistic action of Aspergillus terreus chitozymes

Chitin rich wastes generated from seafood processing industries have become critical concern for coastal area pollution however their transformation into glucosamine (GlcN) could be considered as a value-addition approach. Although, GlcN production through chemical means is in wide practice but, harsh reaction conditions and variable product quality led to urge of biological synthesis. Moreover, the enzymatic means of production need to be explored further to achieve increased production levels of chitozymes that could be employed for GlcN generation. The present study is aimed to develop an integrated process comprised of chemo-thermal pretreatment (to overcome chitin recalcitrance) followed by enzymatic hydrolysis through myco-chitozymes to augment chitin degradation for production of high GlcN titres. Aspergillus terreus has been observed to produce comparatively high titres of chitinase (229 Ul−1), chitosanase (35 Ul−1) and GlcN (213 mg l−1) from shrimp shell chitin as compared to Fusarium pallidoroseum. Utilization of sulphuric acid (2%, w/v) in combination of thermal pretreatment (121 °C, 15 psi, 60 min) was appeared as the most effective pretreatment strategy and resulted into enhanced chitinase (320 Ul−1) and chitosanase (58 Ul−1) production. Augmentation of GlcN production (772 mg l−1) was achieved by synergistic action of chitinase and chitosanase at 2:1 ratio onto pretreated chitin. Thin layer chromatography (TLC) revealed significant production of GlcN via enzymatic hydrolysis. Enhancement in GlcN production through developed chemo-enzymatic method not only provides an eco-friendly, sustainable solution to reduce coastal area pollution but also paves the way to ameliorate industrial production of GlcN in an economic way.

Recovery of Chitin-Glucan Complex in By-products Obtained from Industrial Yeast Fermentation

Chitin-glucan complex (CGC) copolymer is a cell wall component in fungi and yeasts, used in medicine and cosmetics applications. This study investigated the production of CGC from Aureobasidium pullulans KSY-0516, which is used in the industrial production of β-1,3/1,6-glucan. The amino acid composition of the A. pullulans fermentation by-products was determined using an amino acid analyzer. The total amount of amino acid was 6.67 g/100 g of by-product. Additionally, the recovery of the β-glucan complex from the A. pullulans fermentation by-products was 8.44 g/100 g of by-product using ethanol precipitation. The CGC yield was determined from the by-products after yeast fermentation. The recovery of CGC was 14.83% for the yeast cell wall obtained by alkaline extraction. The CGC and β-glucan were characterized using Fourier transform infrared analysis, and compared with crab shell chitin and laminarin. This study aimed to examine the potential, as a useful substrate for biotechnology, by producing CGC from yeast cultivation by-products.

Structural changes in α-chitin through nanofibrillation by high-pressure homogenization in water

Chitin nanofiber was prepared from purified crab shell chitin by repeated high-pressure homogenization in water. The chitin nanofiber/water dispersion thus prepared was viscous and translucent, and maintained a stable dispersion at room temperature for several months. AFM images showed that the chitin nanofibers had heterogeneous network structures with widths ranging from several nanometers to several tens of nanometers. Some kinks and twisted structures were also observed in the AFM images. X-ray diffraction patterns showed that both the crystallinity index and crystal width of the original alpha-chitin decreased with nanofibrillation. Solid-state 13C-NMR spectra showed that the chemical shifts of all carbons were unchanged before and after nanofibrillation, and that all C6–OH groups had the gauche-gauche conformation irrespective of the crystalline fibril surfaces and insides. The degree of N-acetylation increased from 0.83 to 0.98, which was probably due to C2–NH2 groups present in the original chitin being partially removed during high-pressure homogenization in water. The original chitin and chitin nanofiber were dissolved in 8% LiCl/DMAc, and the solutions after dilution to 1% LiCl/DMAc were subjected to size-exclusion chromatography combined with multi-angle laser-light scattering to determine their molar masses and molar mass distributions. The weight-average molar mass (Mw) value of the original chitin was 271,200 (degree of polymerization [DP] ~1340). The Mw value of the chitin nanofiber was 165,500 (DP 820), showing that the DP of the original chitin decreased by 40% through the nanofibrillation in water to form the chitin nanofiber. Chitin nanofibers were prepared from purified crab-shell chitin particles by repeated high-pressure homogenization in water. AFM images showed that the chitin nanofibers had heterogeneous network structures. X-ray diffraction patterns showed that both the crystallinity index and crystal width of the original α-chitin decreased by nanofibrillation. Solid-state 13C-NMR spectra showed that all C6–OH groups had the gauche–gauche conformation. The degree of N-acetylation increased from 0.83 to 0.98 by nanofibrillation, while the weight-average molar masses of the original chitin and chitin nanofibers were 271,200 and 165,500, respectively.

Crustaceous wastes as growth substrates for insect-pathogenic fungus Metarhizium majus UICC 295

The genus Metarhizium consists of a diverse group of species, which have a global distribution and a wide range of insect hosts. Metarhizium majus was reported to inflict 100 % mortality on Oryctes rhinoceros beetle. Feeding activity of the O. rhinoceros beetle causes major crop loss in many coconut and palm oil plantations. This study investigated the use of crustaceous wastes and colloidal chitin as substrates for Metarhizium majus UICC 295 and the fungal virulence on O. rhinoceros larvae. Morphology of M. majus was observed on Sabouraud Dextrose Agar with Yeast Extract (SDAY) added with 5, 10, and 15 % (w/v) powder prepared from crab shell, green mussel shell, shrimp shell, or colloidal chitin and without addition as control. Fungal cultures in 10 % (w/v) crustaceous wastes or colloidal chitin were selected and virulence of M. majus UICC 295 was assayed by dripping the larvae with cell suspension. Untreated larvae were dripped with sterile distilled water and served as control. Mortality was recorded daily for 15 days. Fungal culture prepared from powder of colloidal chitin, green mussel shell and crab shell inflicted 100 % larval mortality in 10, 12, and 13 days, respectively, compared to fungal culture prepared from SDAY in 11 days.

Homologous c-di-GMP-Binding Scr Transcription Factors Orchestrate Biofilm Development in Vibrio parahaemolyticus.

The marine bacterium and human pathogen Vibrio parahaemolyticus rapidly colonizes surfaces by using swarming motility and forming robust biofilms. Entering one of the two colonization programs, swarming motility or sessility, involves differential regulation of many genes, resulting in a dramatic shift in physiology and behavior. V. parahaemolyticus has evolved complex regulation to control these two processes that have opposing outcomes. One mechanism relies on the balance of the second messenger c-di-GMP, where high c-di-GMP favors biofilm formation. V. parahaemolyticus possesses four homologous regulators, the Scr transcription factors, that belong in a Vibrio-specific family of W[F/L/M][T/S]R motif transcriptional regulators, some members of which have been demonstrated to bind c-di-GMP. In this work, we explore the role of these Scr regulators in biofilm development. We show that each protein binds c-di-GMP, that this binding requires a critical R in the binding motif, and that the biofilm-relevant activities of CpsQ, CpsS, and ScrO but not ScrP are dependent upon second messenger binding. ScrO and CpsQ are the primary drivers of biofilm formation, as biofilms are eliminated when both of these regulators are absent. ScrO is most important for capsule expression. CpsQ is most important for RTX-matrix protein expression, although it contributes to capsule expression when c-di-GMP levels are high. Both regulators contribute to O-antigen ligase expression. ScrP works oppositely in a minor role to repress the ligase gene. CpsS plays a regulatory checkpointing role by negatively modulating expression of these biofilm-pertinent genes under fluctuating c-di-GMP conditions. Our work further elucidates the multifactorial network that contributes to biofilm development in V. parahaemolyticusIMPORTANCEVibrio parahaemolyticus can inhabit open ocean, chitinous shells, and the human gut. Such varied habitats and the transitions between them require adaptable regulatory networks controlling energetically expensive behaviors, including swarming motility and biofilm formation, which are promoted by low and high concentrations of the signaling molecule c-di-GMP, respectively. Here, we describe four homologous c-di-GMP-binding Scr transcription factors in V. parahaemolyticus Members of this family of regulators are present in many vibrios, yet their numbers and the natures of their activities differ across species. Our work highlights the distinctive roles that these transcription factors play in dynamically controlling biofilm formation and architecture in V. parahaemolyticus and serves as a powerful example of regulatory network evolution and diversification.

3D-printing methacrylate/chitin nanowhiskers composites via stereolithography: Mechanical and thermal properties

We report on the mechanical and thermal properties of stereolithography (SLA) 3D-printed methacrylate (MA) resin reinforced by chitin nanowhiskers (CNWs). CNWs were synthesized by acid hydrolysis of crab shell chitin and nanocomposites with 0 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt% CNWs loading were prepared by slurry compounding method. The obtained CNWs (diameter = 23 ± 5 nm, length = 253 ± 100 nm, and aspect ratio = 11 ± 3) are well dispersed within the bulk of MA at 1.0 wt% loading, implying good interfacial adhesion between the nanofiller and the resin matrix possibly due to hydrogen bonding interactions. The addition of up to 1.0 wt% CNWs to neat MA enhances the tensile strength, strain at break, modulus, and maximum thermal degradation temperatures of the nanocomposites. Moreover, the incorporation of CNWs not only improves the mechanical and thermal properties, but also preserves the excellent resolution and accuracy of 3D-printed MA/CNWs nanocomposites.

Use of shrimp shell for adsorption of metals present in surface runoff

This research analyzes the use of natural shrimp shell and commercial chitin for biosorption of metal ions in surface runoff. Investigation of the use of these biosorbent materials in drainage systems becomes a management measure for two extremely important issues in Brazil, fish waste management and the surface runoff quality. Methodological procedures involved treatments with different amounts of unprocessed shrimp shell and commercial chitin (5g and 10g) for 200mL of a compensatory drainage mechanism (infiltration swale). The contact time of biosorbent and runoff was 24h and removal of metal ions Fe, Mn, Zn, Cu, Ni, Pb, and Cr was studied. Tests with unprocessed shrimp shell showed high concentrations of metallic ions (Pb, Ni, and Cu) causing contamination of the environment. However, the two biosorbents presented good removal of specific metallic ions (Fe, Mn, Zn, and Cr). These results indicate the need for a biosorbent pre-treatment prior to full-scale use. We indicate the need for a more detailed investigation of water quality in the environment used for shrimp farming. Tests with commercial chitin presented satisfactory results for two concentrations tested. Tests with 10g of commercial chitin allowed removal of all tested metal ions (Fe, Mn, Zn, Cu, Ni, Pb, Cr) with removal percentage between 6.7% and 84.4%. This efficiency may be related to the chitin's composition (shrimp, crustaceans, and crab) and to the chemical process applied to the product prior to commercialization.