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Colloidal solutions of silver nanoparticles (AgNPs) were synthesized by gamma Co-60 irradiation using different stabilizers, namely polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), alginate, and sericin. The particle size measured from TEM images was 4.3, 6.1, 7.6, and 10.2 nm for AgNPs/PVP, AgNPs/PVA, AgNPs/alginate, and AgNPs/sericin, respectively. The influence of different stabilizers on the antibacterial activity of AgNPs was investigated. Results showed that AgNPs/alginate exhibited the highest antibacterial activity against Escherichia coli (E. coli) among the as-synthesized AgNPs. Handwash solution has been prepared using Na lauryl sulfate as surfactant, hydroxyethyl cellulose as binder, and 15 mg/L of AgNPs/alginate as antimicrobial agent. The obtained results on the antibacterial test of handwash for the dilution to 3 mg AgNPs/L showed that the antibacterial efficiency against E. coli was of 74.6%, 89.8%, and 99.0% for the contacted time of 1, 3, and 5 min, respectively. Thus, due to the biocompatibility of alginate extracted from seaweed and highly antimicrobial activity of AgNPs synthesized by gamma Co-60 irradiation, AgNPs/alginate is promising to use as an antimicrobial agent in biomedicine, cosmetic, and in other fields.

Soy protein concentrate (SPC) is a key ingredient in fish feed and most of it originates from Brazil. However, the Brazilian soy industry has reportedly resulted in significant environmental problems including deforestation. Consequently, new sources for protein are investigated and protein extracted from farmed seaweed is considered an alternative. Therefore, we investigate how seaweed protein product (SPP) can compete against SPC as a protein ingredient for fish feed. The study uses the positioning matrix, cost analyses involving the power law, and uncertainty analysis using Monte Carlo simulations, and key research challenges are identified. The initial finding is that, with the emerging seaweed industry, the cost of producing SPP is too high to be competitive for fish feed applications. To overcome this challenge, two solutions are investigated. First, substantial investments in cultivation and processing infrastructure are needed to accomplish scale, and a break-even scale of 65,000 tonnes is suggested. The second but more promising avenue, preferably in combination with the former, is the extraction of seaweed protein and high-value seaweed components. With mannitol and laminaran as co-products to the SPP, there is a 25–30% probability of a positive bottom line. Researches on extraction processes are therefore a necessity to maximize the extraction of value-added ingredients. Over time, it is expected that the competitive position of SPP will improve due to the upscaling of the volume of production as well as better biorefinery processes.

Effect of environmental factors such as exposure to air and desiccation, salinity, temperature, light and photoperiod on tetra spore shedding in the red alga Gracilaria crassa was studied under laboratory condition. In the tetrasporic thalli exposed to air in shade and sun for different durations, maximum quantity of spores were liberated from the thalli in submerged condition in control experiment. Spore output was observed at salinity ranging from 10 to 40% with peak output at 30%. Spore discharge was found at temperature ranging from 20 to 40' C with maximum quantity of spore liberation at 25OC. Spore shedding was recorded at light intensity ranging from 10 to 100 p Em2S^-I with peak discharge at 20 p Em^-2S^-I. Maximum spore release occurred in long day condition at 12 : 12 LD cycle.

Carrageenan seaweed farming based primarily on the cultivation of Kappaphycus and Eucheuma species has grown significantly in the Philippines and Indonesia in the last two decades. Growth has also taken place on a smaller scale in the United Republic of Tanzania and a few other developing countries. Thanks to attributes such as relatively simple farming techniques, low requirements of capital and material inputs, and short production cycles, carrageenan seaweed farming has become a favourable livelihood source for smallholder farmers or fishers and generated substantial socio-economic benefits to marginalized coastal communities in developing countries. However, further development of carrageenan seaweed farming needs to overcome various barriers and constraints such as inclement weather conditions, disease outbreaks, uncertain and fluctuating market conditions, lack of value-added products and value-adding activities in most of seaweed farming countries, low incomes of seaweed farmers in some countries, and occupational health hazards. With six country case studies and one global synthesis, this document attempts to provide a balanced assessment and comparison of the social and economic performance of carrageenan seaweed farming in different countries. Various issues related to seaweed–carrageenan value chains are highlighted. The technical and economic performance of a number of carrageenan seaweed farming cases are systematically evaluated and compared. The positive and negative social impacts of carrageenan seaweed farming are discussed. Issues related to governance and institutions in the sector are reviewed. Challenges and constraints faced by different countries in the future development of their seaweed industries are identified. The document also highlights a series of information and knowledge gaps that need to be filled in order to form a clearer vision of carrageenan seaweed farming development in the future and facilitate evidence-based policy decision-making and sector management.