Seagrapes for food, cosmetics and industrial applications
Popularly known as “Green Caviar,” the seagrape (Caulerpa lentillifera) is a seaweed salad and delicacy in Japan, Korea and other Southeast Asian and Pacific island countries. In Japan, where it is known as “umibudo,” the seagrape is grown seasonally in tanks in the southern island of Okinawa. It is noted for its succulent, salty taste, with miniature grapelike structures along its stem. Marine scientists at Poseidon and SHMRC have re-discovered a seagrape subtype, called kadalchiratchai, formerly thought to be extinct in the southern east coast of Tamil Nadu, India. This seagrape, with its finer, more delicate ’grapes’ have been successfully mono-cultured artificially under land-based raceways to produce the seaweed year-round under controlled conditions that allow optimization of growth, purity and maximize expression of bioactive ingredients. This brief report describes the exciting discovery effort, the struggle to build the capability for mass culture and the promising opportunities for use of kadalchiratchai as food and as raw material for discovery of unique bioactive ingredients for the cosmetic and biomedical industries.
Caulerpa lentillifera was first reported in Krusadai island in the Gulf of Mannar in 1955, but was never recorded again even after repeated marine surveys . This species was thought to have become extinct from Indian waters until Mantri in 2004 reported the discovery of this species in Samiani Island situated in the mouth of Gulf of Kutch in the West Coast of India. Our marine science discovery programme considered the seagrape project of sufficient national importance to warrant a more extensive survey to locate this species along the Gulf of Mannar where it was originally reported.
A survey using traditional methods is no longer possible because Krusadai Island is part of the restricted and protected marine reserve. We were unable to locate distinct beds of seagrapes along the coastal areas from Tuticorin and Mandapam. We attempted an alternative method wherein samples of mixed seaweeds species from the near shore areas along Kilakarai were collected at low tide, kept moist with seawater and immediately brought to the laboratory. Careful examination of the seaweed biomass revealed the presence of one or more branches of C. lentillifera (see figure below). The biomass comprised predominantly of C. racemosa and other minor seaweeds, such as C. sertularioides, Enteromorpha flexuosa and C. peltata. C. lentillifera represented approximately 0.01 % of the total collected biomass.
Mariculture of seagrapes
A total of 16 grams of live seagrapes were collected manually from the biomass harvested from the wild on July 27, 2008. These were transferred to a 1 m3 fiber glass tank filled with 0.4 m3 of seawater. The sandy-muddy substratum was placed at the bottom to a height of 8 cm and the seagrape fragments were planted directly on the substratum. The tank culture was protected from direct sunlight and dilution by rainwater using a translucent cover. Seawater was pumped from the sea and 50% of the seawater in the tank was replaced with new seawater every 4 days. No fertilization was used since there was adequate nutrient available in normal seawater exchange to sustain growth of the seagrape at low biomass level. From the initial 16 g of live seagrapes, the cultured biomass grew to 12.4 kg by January 24, 2009, i.e., after 6 months in tank culture. To validate the rate of growth, many tanks were prepared in a similar fashion and each tank was inoculated with 500 g of seagrapes.
Although the seagrapes did not show any growth for the first week after planting, vigorous growth started from week 2. The growth of the seagrapes slowed down by the 4th and 5th week in tank culture. The seagrapes grew well in artificial culture and produced longer stolons and denser ramuli compared to those collected in the wild. The estimated doubling time was 15 days (see bar graph below).
FOOD INDUSTRY APPLICATIONS
The discovery of native population of C. lentillifera in the Gulf of Mannar in concert with the successful demonstration of cultivation of this species opens unique commercial opportunities in the future for a new industry in India. The coastal areas along the Gulf of Mannar are more suitable compared to other tropical countries because of very short monsoons. Seagrapes are highly vulnerable to decline in salinity during the rainy season. For this reason, mariculture in open ponds in Philippines, Thailand and Vietnam occur only during the dry season. In Japan, culture of seagrapes is limited to the warmer southern island of Okinawa. Wild collections are only possible during the summer months so that most of the mariculture activities are in artificial tanks inside expensive artificially heated greenhouses. To prevent crop loss and to have better control of the quality of seagrapes, land based mariculture of C. lentillifera in artificial tanks was developed. The market acceptability of cultured Indian seagrapes, we refer to in the Tamil language as kadalchiratchai, will require substantial efforts in research and development to improve crop quality. Improved technologies in processing, packaging and transport of fresh and preserved seagrapes are under development to enable successful worldwide market.
BIOACTIVES FOR COSMETIC INDUSTRY
Aside from being a high value food item, recent scientific studies point to its other industrial and biomedical uses. Seaweeds, in general, possess many bioactive ingredients that are now in common use in the cosmetic industry as additive to give high value to topical formulations, such as anti-inflammatory, skin lightening and other benefits. Many species of Caulerpa have been shown to possess anti-oxidant, anti-viral, hypolipidaemic and anti-cancer properties. It is very likely that seagrapes may possess similar biopharmaceutical attributes as more research is focused towards this direction. A concerted effort to utilize this resource in identifying promising ingredients open new opportunities that may provide unique cosmetic benefits. Since kadalchiratchai seagrapes can be grown all year round under controlled conditions, it is possible to maximize the production of such ingredients. Since scaling up of mass production can now be achieved, a chemical identification and processing of such bioactive ingredients is possible through strategic alliances.