Antibiofilm Effects of Heated Scallop Shell Powder on Campylobacter jejuni Biofilms

Methods to reuse large numbers of scallop shells from the harvesting regions of Japan are being explored. The major component of scallop shells is calcium carbonate (CaCO3), which forms the powerful bactericidal agent, calcium oxide (CaO), when heated. Heated scallop shell powder (HSSP) exhibits strong and broad-spectrum antimicrobial activity against bacteria, fungi, and viruses. This study investigated the antibiofilm activity of HSSP against the biofilms of Campylobacter jejuni, which is the predominant species in campylobacteriosis. Biofilm samples of C. jejuni were prepared on 0.45 µm filter paper under microaerobic conditions. The HSSP treatment inactivated and eradicated C. jejuni biofilms. The resistance of C. jejuni biofilms to HSSP was significantly higher than that of the floating cells. Moreover, the antibiofilm activity of the HSSP treatment against C. jejuni biofilms was higher than that of NaOH treatment at the same pH. These results indicated that HSSP treatment is an effective method for controlling C. jejuni biofilms.

Plasticity in organic composition maintains biomechanical performance in shells of juvenile scallops exposed to altered temperature and pH conditions

The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (~ 7.7) and control conditions (pH ~ 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 °C), shell microhardness increased. Other biomechanical properties were not affected by pH/temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.

Simple and Rapid Synthesis of Calcium Acetate from Scallop Shells to Reduce Environmental Issues

The search for sustainable resources remains a subject of global interest. Calcium acetate used in many fields was prepared using waste scallop shell as a raw material, and its physicochemical properties were investigated. The waste scallop shells were transformed to calcium acetate compounds by reactions with four acetic acid concentrations at ambient temperature until the completely dried powder is obtained. The maximum yield of 87% with short reaction time at a low temperature was observed in the reaction of 60%w/w acetic acid with scallop shells. Thermal transformation reactions of all prepared calcium acetate samples revealed temperature conditions for heating to produce other advanced materials. FTIR and XRD results confirmed the purity and solid phase of all prepared calcium acetate samples, and they were compared with those of literatures and found to be well consistent. The obtained timber-like particles have different sizes depending on the acetic acid concentration. This work reports an easy and low-cost method with no environmental effect to produce cheap calcium products to be used in the industry.

The Potential of Engay Food Enriched with Asian Scallops Flour for Dysphagia Food Alternative

Engay food is a Japanese term for a modified texture food for elderly people with dysphagia. The enrichment of the nutritional value of food is carried out by adding the calcium found in the scallop shells. This study aimed to investigate the chemical, physical, and sensory properties of engay food enrich with scallop shell flour. The food formulation consisted of milkfish and the addition of scallop shell flour as much as 0%, 2%, 4%, 6%, and 8% of the basic ingredients with 5 repetitions. The result showed, the best formulation of engay food from chemical, physical, and sensory was the concentration of 4% scallop shell flour with the calcium content of 0.099 mg / 100g, water content 68.97%, ash content 0.98%, fat 1.39%, protein 9.00%, carbohydrates 19.66% and contains 562 cal / 100g. L* 30.8, a* 2.4, b* 13.9, °Chroma 14.07, and °Hue 80.27 with the type of yellow-red color, cohesiveness value 0.334 J / m2, adhesion value 0.034 mJ, and gumminess value 206.176 N/m2. High calcium engay food with milkfish as the main ingredient can be used as an alternative food for elderly people with dysphagia because it meets the requirements for food categories level 4-5 based on IDDSI recommendation.

Antibacterial Properties of Scallop Shell Derived Calcium Hydroxide Powders

Globally increased bivalve aquaculture production results in a vast amount of by-product discharges such as scallop shells. Utilization of these wastes to produce new products such as antibacterial agents can cooperate to reduce environmental problems and provide a high value-added product at a lower cost. In this study, scallop shells are heat-treated at 800°, 900°, 1000°, and 1100°C for 4 hours at atmospheric conditions. X-ray diffraction analysis revealed that calcium carbonate is the only inorganic phase in the powdered scallop shells. Ten weeks after the thermal treatment of the scallop shells, the calcium hydroxide phase was the only crystalline phase determined by X-ray diffraction analysis for the samples calcined at 1000° and 1100°C. At lower calcination temperatures, calcium carbonate and calcium hydroxide phases were co-existing in the samples. Scanning electron microscopy investigations depicted that using scallop shells as a starting material to synthesize nanometer-sized calcium hydroxide is achieved. It was determined that applied calcination temperature has a significant effect on the particle size of the obtained calcium hydroxide phase. Antimicrobial activity of calcined and uncalcined shell powders were tested against Escherichia coli and Staphylococcus aureus. No antibacterial activity was detected for the uncalcined scallop shell powders. However strong antibacterial activity was determined for the powders after subjection to calcination. Calcination of scallop shells is an environmentally friendly, readily applied, and low- cost approach to achieve nanometer-size calcium hydroxide that can be used as an inorganic antibacterial material in various composite systems.

In Situ Geochemical Analysis of Organics in Growth Lines of Antarctic Scallop Shells: Implications for Sclerochronology

Bivalve shells are extensively used as bioarchives for paleoclimate and paleoenvironmental reconstructions. Proxy calibrations in recent shells are the basis for sclerochronology and the applications of geochemistry data to fossils. Shell geochemical information, however, could be altered with the disappearance of intercrystalline organic matrix components, including those linked to shell growth increments, during early diagenesis. Thus, an evaluation of the chemistry of such organics is needed for the correct use of sclerochronological records in fossil shells. Here, we use atom probe tomography (APT) for in situ geochemical characterization of the insoluble organic matrix in shell growth increments in the Antarctic scallop, Adamussium colbecki. We confirm the presence of carboxylated S-rich proteoglycans, possibly involved in calcite nucleation and growth in these scallops, with significant concentrations of magnesium and calcium. Diagenetic modification of these organic components could impact proxy data based on Mg/Ca ratios, but more importantly the use of the δ15N proxy, since most of the shell nitrogen is likely bound to the amide groups of proteins. Overall, our findings reinforce the idea that shell organics need to be accounted for in the understanding of geochemical proxies.

Hydrothermal Hot Pressing of CaCO3-Chitosan Composites with High CaCO3 Content

In this study, a hydrothermal hot pressing (HHP) method was used for the preparation of molded composites with high CaCO3 content. Specifically, composites consisting of chemically synthesized CaCO3 and chitosan and scallop shells milled with a ball mill were molded by the HHP method; the structures, mechanical properties, and vibration absorption characteristics of the resulting disc-shaped molded composites were investigated. All the composites had high CaCO3 contents (93%); flexural strengths (several megapascals) comparable to those of limestone and cement; and vibration absorption characteristics (logarithmic attenuation factors of 0.07–0.18) superior to those of aluminum alloys, stainless steel, and ceramics (which have logarithmic attenuation factors of <0.01). The composites prepared from the CaCO3-chitosan composites can be expected to find application as light-control materials, as materials for controlling the propagation of light, sound, and vibration waves including vibration-isolating materials and as CO2-fixation materials.