Characterization of a C-Type Lectin Domain-Containing Protein with Antibacterial Activity from Pacific Abalone (Haliotis discus hannai)

Genes that influence the growth of Pacific abalone (Haliotis discus hannai) may improve the productivity of the aquaculture industry. Previous research demonstrated that the differential expression of a gene encoding a C-type lectin domain-containing protein (CTLD) was associated with a faster growth in Pacific abalone. We analyzed this gene and identified an open reading frame that consisted of 145 amino acids. The sequence showed a significant homology to other genes that encode CTLDs in the genus Haliotis. Expression profiling analysis at different developmental stages and from various tissues showed that the gene was first expressed at approximately 50 days after fertilization (shell length of 2.47 ± 0.13 mm). In adult Pacific abalone, the gene was strongly expressed in the epipodium, gill, and mantle. Recombinant Pacific abalone CTLD purified from Escherichia coli exhibited antimicrobial activity against several Gram-positive bacteria (Bacillus subtilis, Streptococcus iniae, and Lactococcus garvieae) and Gram-negative bacteria (Vibrio alginolyticus and Vibrio harveyi). We also performed bacterial agglutination assays in the presence of Ca2+, as well as bacterial binding assays in the presence of the detergent dodecyl maltoside. Incubation with E. coli and B. subtilis cells suggested that the CTLD stimulated Ca2+-dependent bacterial agglutination. Our results suggest that this novel Pacific abalone CTLD is important for the pathogen recognition in the gastropod host defense mechanism.

Development of a Convenient Home Meal Replacement Product Containing Roasted Abalone (Haliotis discus hannai) with Honey Butter Sauce

Abalone (Haliotis discus hannai) has high nutritional value and market demand. However, it is generally sold as a raw product, which suffers from lengthy preparation, low commercial value, and a short shelf life. To address these problems, we processed abalone as a home meal replacement (HMR) product using superheated steam and quick freezing technology. Response surface methodology was used to optimize the roasting process. A test HMR product was produced by mixing roasted abalone with honey butter sauce at a ratio of 70:30 (w/w), then evaluated for its physicochemical, biological, and nutritional characteristics and shelf life. Roasting abalone at 220 °C for 2 min resulted in high scores for hardness and overall acceptance. The roasting process successfully maintained the chemical characteristics of abalone, including pH, volatile basic nitrogen, and thiobarbituric acid-reactive substances. The sensory characteristics of the test HMR product were maintained using quick freezing methods. Moreover, nutritional analysis revealed that the test HMR product contained macro- and micronutrients, amino acids, and fatty acids, which could contribute to meeting daily nutritional needs. The estimated shelf life of the product was 30 months. Therefore, this study successfully developed a high-quality HMR product containing abalone.

Effects of Various Extraction Factors on Protein Yield of Haliotis discus hannai (Abalone)

Abalone (Haliotis discus hannai) is a widely consumed seafood in Asian countries. Rich in protein, abalone is consumed for refreshment, pregnancy care, and vitality. Although many studies have found that abalone protein has beneficial effects, the efficiency of the protein extraction method for abalone has rarely been studied. Therefore, this study aimed to examine the effects of various factors of abalone protein extraction, including extraction buffer, sonication, salt (NaCl) concentration, surfactant, and heating. Phosphate buffer showed higher protein yield compared with Tris-HCl buffer. In addition, the highest protein yield for each factor was observed at 60 s of sonication (84.44 µg/mg dw), 0.6 M NaCl (141.9 µg/mg dw), and 16 mM sodium dodecyl sulfate (SDS) (253.15 µg/mg dw). However, a combined effect was not observed. Lower protein extraction efficiency was observed for sous vide-cooked abalone. The electrophoresis assay revealed myofibrillar proteins, including paramyosin, actin, and tropomyosin. Overall, our results demonstrate that various extract conditions affect the protein extraction of abalone.