Since Japan has a highly developed fermentation technology, many industrial companies, in collaboration with some university groups (14), have tried to apply this technology for the commercial production of useful compounds. The Japan Tobacco Inc.'s interest involved around mass-production of tobacco cells as raw materials of cigarettes; the company established 20 kL fermentors which were the largest for plant cells in 1970's. Meiji Seika in Japan also elucidated the fundamentals of production of Panax ginseng cells in large volumes. Researchers reported that cultured ginseng cells stimulated physiological activities in animals in a similar fashion as elicited by native ginseng roots. The work was followed by Nitto Denko Co. which has been manufacturing cell mass of ginseng commercially. The cells are used as health foods in Japan. Researchers of Kyowa Hakko conducted extensive pharmacological screening of numerous cell cultures and found various novel products of great interest, including plasmin inhibitory proteins in Scopolia japonica cells and plant virus inhibitors in cultured cells of Phytolacca americana and other species (15). The virus inhibitors of P. americana are now being studied by many research groups in the world because of their activity against AIDS and other animal viruses. Other firms such as Ajinomoto and Nippon Shin-yaku also made efforts to increase the level of accumulation of alkaloids, steroids and other secondary products in cultured cells.

Groups in Germany outlined very interesting approaches to industrial application (16) in the meeting held in 1976 at Munich, and their excellent results encouraged researchers in other countries. For example, Zenk and his colleagues (17) presented an impressive paper in which they successfully selected high-alkaloid producing cell lines of Catharanthus roseus using a method similar to the microbial mono-colony isolation technique. A number of laboratories in industries and universities followed Zenk's approach, and in fact, some researchers could increase significantly the level of secondary products such as ubiquinone-10, biotin, and various plant pigments produced by cell cultures.

In 1982, the 5th International Congress of Plant Tissue and Cell Cultures was held in Japan and about 70 out of 372 papers presented there related to production of secondary metabolites in cultured cells and several papers seemed to be commercially promising such as production of shikonin by Fujita et al. (19) of Mitsui Petrochemical and that of several antitumor compounds by Misawa et al. of Kyowa Hakko (20).

At subsequent International Congress of Plant Tissue and Cell Cultures in Minneapolis in 1986 and that in Amsterdam in 1990 as well as other meetings such as the Meeting of Primary and Secondary Metabolism of Plant Cell Cultures held in Giessen, Germany and the 4th and International Congress on Phytotherapy held in Munich, Germany in September, 1992, many compounds were shown to be accumulated by plant cell cultures and many different strategies were presented to increase their productivity. Means for production of those compounds include not only de novo synthesis but also biotransformation processes. A biotransformation process to produce ß-methyl digoxin using Digitalis lanata cells studied by Reinhard and Alfermann in Germany (21) was evaluated by Boehringer Mannheim Co. using 4 kL bioreactors although it has not yet been commercialized.

A combination of a plant cell culture process and a simple chemical coupling reaction was invented by a Canadian company, Allelix (22), to manufacture vinblastine as a commercially feasible process. The technology is now being studied by Mitsui Petrochemical in Japan for commercialization.

Sanguinarine production was also studied by Kurz et al. (82) in Canada since this alkaloid has a market in the denatal care field.

The recent biotechnology boom has triggered increase interest in plant cell cultures, for example, a number of firms and academic institutions in the U.S., Japan, Canada, and Europe have been investigating intensively the production of a very promising anti-tumor compound, taxol, using this technology.