Kerala University of Fisheries and Ocean Studies

This study investigated the sustainable extraction of nano-hydroxyapatite (n-HAP) from Skipjack tuna ( Katsuwonus pelamis ) and Nile tilapia ( Oreochromis niloticus ) bone side streams via thermal calcination at 900 °C for 9 h. The physicochemical and biocompatibility characteristics of the resulting n-HAP were systematically evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray (SEM-EDS), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and zeta potential measurements. XRD revealed high crystallinity of 76.4% (tuna) and 74.4% (tilapia). TEM confirmed nano-scale structures of 44.9 nm (tuna) and 153.3 nm (tilapia). The Ca/P ratios were 1.72 for tuna and tilapia, and the zeta potential results (−41.1 mV for tuna and −38.3 mV for tilapia) indicated good colloidal stability. FTIR spectra confirmed characteristic phosphate and hydroxyl groups. Both tuna- and tilapia-derived n-HAP exhibited reduced cell viability at 24 h (75.5–80.2%) relative to the control, followed by partial recovery at 72 h (77.5–81.1%). Unlike earlier studies on single fish species, this work presents a comparative evaluation of two different fish bone sources, revealing promising potential for their application in medical scaffolds due to their acceptable preliminary cytocompatibility, stability, and eco-friendly sourcing. • Nano-hydroxyapatite extracted from tuna and tilapia bones via calcination. • Comparative evaluation of physicochemical and biocompatibility profiles. • Stable, non-toxic n-HAP promising for medical scaffolds. • Supports eco-friendly valorization of fish processing side streams.

Synthetic biology, an interdisciplinary field combining biology, engineering, and computational science, serves as a tool for the advancement of environmental management by synthesizing new organisms with enhanced abilities to combat pollution, resource depletion, and ecological damage. This chapter explores the role of synthetic biology in environmental applications, focusing on the use of engineered microorganisms for pollution remediation, carbon capture, and resource recovery. By designing and optimizing genetic circuits, researchers can create microorganisms with unique metabolic pathways that efficiently degrade toxic pollutants, such as heavy metals, pesticides, and hydrocarbons, or capture greenhouse gases like carbon dioxide and methane. Synthetic biology also enables the creation of biosensors that detect environmental contaminants with high sensitivity and specificity, providing early warning systems for environmental threats. The chapter further discusses the integration of microbial systems into bio-based production processes and the principles as well as tools of synthetic biology, such as gene circuits, metabolic engineering, and the application of these innovations to tackle environmental challenges in wastewater treatment, soil bioremediation, and air quality management. The use of synthetic biology to create organisms capable of converting waste into biofuels, bioplastics, or valuable chemicals, reducing reliance on fossil fuels and minimizing waste generation, was also reviewed in detail. Additionally, the potential risks and ethical considerations associated with the release of Genetically Modified Organisms (GMOs) into natural ecosystems are addressed, emphasizing the need for safety protocols and regulatory frameworks. The way towards the future directions in synthetic biology, such as the development of synthetic ecosystems and the use of artificial intelligence to design more complex genetic networks, will render synthetic biology a powerful tool for environmental protection and pollution mitigation.

Goldflag jobfish Pristipomoides auricilla (Jordan, Evermann and Tanaka, 1927) and goldbanded jobfish Pristipomoides multidens (Day, 1871) were recently recorded from the southeastern Arabian Sea, marking an occasional occurrence. The samples of P. auricilla and P. multidens were collected from the hook and line fishery off Kochi, southwest coast of India and described here based on the morphometric and meristic characteristics. P. auricilla is distinguished by a triangular vomerine tooth patch, 73–74 lateral-line scales, and 28 gill rakers (10 + 18), whereas P. multidens differs by having 51 lateral-line scales, 19 gill rakers (8 + 11), and two prominent golden bands on the snout and cheek. This study provides specimen-based confirmation of P. auricilla from the southeastern Arabian Sea and clarifies its range extension into Indian waters, while also documenting the verified occurrence of P. multidens at Kochi—where it had not been previously collected—along with comparative diagnostic features for accurate identification. The insights from this work are vital for effective fishery management and conservation strategies, particularly in the context of India’s rich but underexplored marine ecosystems. Furthermore, this research contributes to global efforts in monitoring and assessing deep-water snapper species.

The black sea urchin, Stomopneustes variolaris, a prominent species in the Bay of Bengal, India, was investigated for its spawning, embryonic, and larval development under laboratory conditions (25–28 °C, 30–33‰ salinity). Analysis of gonad indices revealed peak values (g) from October (4.90 ± 2.5) to January (5.31 ± 5.6). Unfertilized eggs had a mean diameter of 75.20–80.63 µm, and fertilization success was high at 90%. Early embryonic stages, including the 2-cell, 4-cell, 8-cell, 16-cell, 32-cell, and morula stages, were observed within 5.30 h post-fertilization. Blastula and gastrula stages were reached at 18.15 h and 19.10 h, respectively, followed by the prism stage at 23.20 h. Pluteus larval development progressed from 2-arm (33.35 h) to 4-arm (day 4) and 6-arm (day 12). Larvae were successfully reared on a mixed microalgal diet comprising Dunaliella salina, Chaetoceros gracilis, Chaetoceros calcitrans, and Isochrysis galbana. Metamorphic competence was achieved between 25- and 30-days post-fertilization. This study makes a significant contribution to understanding the reproductive biology and early life history of S. variolaris, offering a foundational basis for developing effective strategies for induced breeding, seed production, and aquaculture strategies for this species in captivity along the Indian coast.

This study evaluated the effectiveness of a 0.5% α-chitosan edible coating in preserving the quality of squid (Uroteuthis duvaucelii) rings during chilled storage at 4 °C. The coated samples (Tα) and uncoated controls (C) were assessed over 8 days for physicochemical parameters (colour, pH, drip loss, lipid oxidation) and sensory attributes. Results showed that α-chitosan substantially retarded quality deterioration compared to the control. Lightness (L*) decreased sharply in the control, whereas coated samples maintained higher values. Redness (a*) and yellowness (b*) increased more gradually in coated samples, indicating reduced surface oxidation. The rise in pH was significantly suppressed in coated samples relative to the control, suggesting reduced microbial spoilage. Drip loss reached 6.5% in the control but remained significantly lower (3.8%) in coated samples, while TBA values an indicator of lipid oxidation were markedly reduced in the coated group compared to the control. Sensory evaluation further confirmed the preservative effect, with coated samples retaining acceptable odour, texture, and overall acceptability up to Day 8, whereas control samples fell below the acceptability threshold by Day 6. Overall, α-chitosan coating acted as an effective oxygen- and moisture-barrier, slowing biochemical and oxidative spoilage processes and extending the sensory shelf life of squid rings by at least two days. These findings highlight α-chitosan as a promising natural bio-preservative for enhancing the storage stability and commercial quality of cephalopod products.