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This study aimed to evaluate and compare the quality of κ-carrageenan obtained from tissue-cultured and fieldcultured Kappaphycus alvarezii. Carrageenan properties including yield, viscosity, gel strength and sulfate content were studied. After 60 days of cultivation, tissue-cultured K. alvarezii showed a higher growth rate (6.3 ± 0.01% day −1 ) than field-cultured seedlings (3.4 ± 0.3% day −1 ). The obtained carrageenan yield from tissue-cultured (67.3 ± 16.4%) was higher than field-cultured K. alvarezii (51.5 ± 21.0%). Gel viscosity of carrageenans from tissue-cultured K. alvarezii (1280.0 ± 25.0 cP) was found significantly higher than field-cultured samples (87.8 ± 20.9 cP). The 1.5% gel solution of tissue-cultured and field-cultured K. alvarezii exhibited gel strengths of 703.5 ± 14.1 and 288.3 ± 19.3 g cm −2 , respectively. The average sulfate content of carrageenans was found to be significantly different between tissue-cultured and fieldcultured K. alvarezii with 34.2 ± 10.9 and 7.5 ± 6.7%, respectively. Tissue culture is recommended to produce high quality seedlings by providing optimized culture conditions to the seaweed. This approach can serve as an alternative way to solve the seedling shortage problems currently faced by the seaweed industry.

Seaweed farming has been identified as one of the entry point projects (EPPs) in Malaysia since the government introduced the Economic Transformation Programme, which aims to increase seaweed production to 150,000 t annually by 2020. To achieve this goal, micropropagation and subsequent acclimatization of the micropropagated seaweeds to the open sea is one of the available options to solve the seedling shortage problem. Acclimatization is an important process in which micropropagated seaweeds adjust to gradual changes in environments such as temperature, humidity, photoperiod, and pH. Success acclimatization is an important key for the seaweed tissue culture industry to move forward, and therefore, the protocol of acclimatization of micropropagated Kappaphycus alvarezii has been extensively optimized in this study. Direct planting out of the micropropagated seaweeds to the open sea without goingthrough the nursery acclimatization phase may cause shock to the seaweeds due to sudden changes in environmental conditions. In a 2-week acclimatization study, seedlings were found to achieve optimum growth when cultivated in seawater enriched with mixed-algae fertilizer, natural seaweed extract (NSE), under a regimen of daily medium change and culture density of 0.40 g L −1 . The acclimatized K. alvarezii has achieved 83.33 ± 5.77 % of survival in the seaweed farm with normal physiology and no epiphyte coverage. This study has provided useful information for seaweed cultivators to enhance the survival rate of micropropagated K. alvarezii through nursery acclimatization prior to serve as seedlings for commercial seaweed cultivation.

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Modern seaweed farming relies heavily on seedlings from natural beds or vegetative cuttings from previous harvests. However, this farming method has some disadvantages, such as physiological variation in the seed stock and decreased genetic variability, which reduces the growth rate, carrageenan yield, and gel strength of the seaweeds. A new method of seedling production that is sustainable, scalable, and produces a large number of high-quality plantlets is needed to support the seaweed farming industry. Recent use of tissue culture and micropropagation techniques in eucheumatoid seaweed production has yielded promising results in increasing seed supply and growing uniform seedlings in large numbers in a shorter time. Several seaweed species have been successfully cultured and regenerated into new plantlets in laboratories using direct regeneration, callus culture, and protoplast culture. The use of biostimulants and plant growth regulators in culture media increases the seedling quality even further. Seedlings produced by micropropagation grew faster and had better biochemical properties than conventionally cultivated seedlings. Before being transferred to a land-based grow-out system or ocean nets for farming, tissue-cultured seedlings were recommended to undergo an acclimatization process to increase their survival rate. Regular monitoring is needed to prevent disease and pest infestations and grazing by herbivorous fish and turtles during the farming process. The current review discusses recent techniques for producing eucheumatoid and other valuable seaweed farming materials, emphasizing the efficiency of micropropagation and the transition from laboratory culture to cultivation in land-based or open-sea grow-out systems to elucidate optimal conditions for sustainable seaweed production.

Carrageenan is a polysaccharide derived from red algae (seaweed) with enormous economic potential in a wide range of industries, including pharmaceuticals, food, cosmetics, printing, and textiles. Carrageenan is primarily produced through aquaculture-based seaweed farming, with Eucheuma and Kappaphycus species accounting for more than 90% of global output. There are three major types of carrageenan found in red algae: kappa (κ)-, iota (ι)-, and lambda (λ)-carrageenan. Kappaphycus alvarezii is the most common kappa-carrageenan source, and it is primarily farmed in Asian countries such as Indonesia, the Philippines, Vietnam, and Malaysia. Carrageenan extracted from K. alvarezii has recently received a lot of attention due to its economic potential in a wide range of applications. This review will discuss K. alvarezii carrageenan in terms of metabolic and physicochemical structure, extraction methods and factors affecting production yield, as well as current and future applications.