Page 274 - Algae Anatomy, Biochemistry, and Biotechnology

Algae and Men 257

for equally valuable products from other groups, especially on the central and northern coasts of
British Columbia and Alaska. P. abbottae is valued also for its medicinal properties as gastro-
intestinal aid, taken as decoction or applied as a poultice for any kind of sickness in the
stomach, and as orthopedic aid applied on broken collarbones.
Nearly 133 species of Porphyra have been reported from all over the world, which includes 28
species from Japan, 30 from North Atlantic coasts of Europe and America, and 27 species from the
Pacific coast of Canada and United States. Seven species have been reported from the Indian coast,
but they are not exploited commercially.
Porphyra grows as a very thin, flat, blade, which can be yellow, olive, pink, or purple. It can be
either round, round to ovate, obovate, linear or linear lanceolate, from 5 to 35 cm in length. The
thalli are either one or two cells thick, and each cell has one or two stellate chloroplasts with a pyr-
enoid. Porphyra has a heteromorphic life cycle with an alternation between an aploid gametophyte
consisting of a macroscopic foliose thallus, which is eaten, and a filamentous diploid sporophyte
called conchocelis phase. This diploid conchocelis phase in the life cycle was earlier thought to
be Conchocelis rosea, a shell-boring independent organism. Understanding that these two phases
were connected was a major research advance made in 1949 in Britain, when Drew demonstrated
in culture that Porphyra umbilicalis (L.) Ku ¨tz had a diploid conchocelis phase. Until this landmark
work, cultivation of Porphyra was developed intuitively, by observing the seasonal appearance of
spores, but nobody knew where the spores came from, so there was little control over the whole
cultivation process. Drew’s findings completely revolutionized and transformed the Porphyra
industry in Japan and subsequently throughout Asia, allowing indoor mass cultivation of the fila-
mentous form in sterilized oyster shells and the seeding of conchospores directly onto nets for out-
planting in the sea. All Japanese species of Porphyra investigated so far produce the conchocelis
phase, which can be maintained for long periods of time in free culture. It grows vegetatively
under a wide range of temperature, irradiances, and photoperiods, and it is probably a perennial
persistent stage in the life history of many species in nature as well.
Since Drew’s time, cultivation has flourished, and now accounts for virtually all the production
in China, Japan, and the Republic of Korea. Japan produces about 600,000 wet tons of edible
macroalgae annually, around 75% of which is for nori. In 1999, the combined annual production
from these three countries was just over 1,000,000 wet tons. Nori is a high value product, worth
approximately US$16,000/dry tons. Japanese cultivation of Porphyra yields about 40,000 wet
tons/year and this is processed into ca. 10 billion nori sheets (each 20 20 cm, 3.5–4.0 g), repre-
senting an annual income of 1500 million U.S. dollars. In the Republic of Korea, cultivation
produces 270,000 wet tons, while China produces 210,000 wet tons.
Processing of wet Porphyra into dried sheets of nori has become highly mechanized, by an
adaptation of the paper-making process. Wet Porphyra is rinsed, chopped into small pieces, and
stirred in a slurry. It is then poured onto mats or frames, most of the water drains away, and the
mats run through a dryer. The sheets are peeled from the mats and packed in bundles of ten for
sale. This product is called hoshi-nori, which distinguishes it from yaki-nori, which is toasted.
Nori is used mainly as a luxury food. It is often wrapped around the rice ball of sushi, a typical
Japanese food consisting of a small handful of boiled rice with a slice of raw fish on the top. It
can be incorporated into soy sauce and boiled down to give an appetizing luxury sauce. It is also
used as a raw material for jam and wine. In China it is mostly used in soups and for seasoning
fried foods. In the Republic of Korea it has uses similar to Japan.
Dried nori is in constant oversupply in Japan and producers and dealers are trying to encourage
its use in the U.S. and other countries. Production and markets in China are expanding, although the
quality of the product is not always as good as that from the Republic of Korea and Japan.
The fronds of the red alga Palmaria (Rodimenia) palmata (Florideophyceae) are known as
“dulse” (see Chapter 1, Figure 1.15); they are eaten raw as a vegetable substitute or dried and
eaten as a condiment in North America and Europe (Brittany, Ireland, and Iceland). Natives of
Alaska consume the fronds fresh or singed on a hot stove, or add the air-dried fronds to soups