Herbal medicines on tap
Australian scientists are working on a unique method of producing commercial quantities of herbal medicine.
Scientists from Food Science Australia and others partners in the Cooperative Research Centre (CRC) for Bioproducts are developing the method for mass production of the extracts from popular herbs such as Echinacea, Ginseng and Gynostemma.
"Some of these plants grow very slowly and demand is greater than supply," said Dr Philip Franks, Food Science Australia's leader of biotechnology research. "For example, the Ginseng plant takes seven years to grow to maturity."
The research consortium has been approached by the Chinese Government to explore the possibility of mass-producing the bioactive chemicals in Ginseng.
The method builds on existing techniques that use plant cells as factories to produce large amounts of natural chemicals in fermentation tanks. Currently, Ginseng, natural food colouring agents and the anti-cancer agent taxol are produced in this way.
Dr Franks said these current methods use individual plant cells in a suspension with the consistency of "apple sauce". The resulting product may or may not contain significant levels of the active ingredient.
"The trick is to tweak the fermentation to maximize levels of the particular active constituent," he said. This is why the researchers have chosen to use so-called hairy roots as a tissue culture.
Hairy roots are formed on plants when they are infected by the bacteria, Agrobacterium rhizogenes. They are very fine hairs that grow on any part of the plant - leaf, stem, petal, as well as root.
These fine hairs allow a more effective fermentation process because they grow very rapidly. The fact that they are plant tissue rather than individual plant cells also offers an advantage, said Dr Franks.
"The active constituents of Ginseng may only be able to be produced by plant tissue, rather than single cells in suspension," he said. "This is because in a tissue, plant cells can work as a team and produce complex chemicals."
According to Dr Franks, the bioactive chemicals in Echinacea extracts from field-grown plants are found primarily in the roots, but can also be found in leaves. In their fermentation work the researchers keep their options open by examining cell cultures from all sources.
"Our ultimate focus is on a realistic commercial process and we select the cell line based on its productivity rather than on the origin of the tissue," said Dr Franks.
Dr Franks said the current challenge was to scale up the production through identifying the right food and oxygen supply, and to overcome the natural tendency of the hairy roots in the fermenter to become tangled and hinder aeration.
The researchers are currently producing active ingredients from Echinacea in 10 L tanks, Ginseng in 1000L tanks and have a 10,000L pilot plant up and running producing a biopoymer used as an emulsifier.
"We think it's possible for Australia to have a new industry based on plant cell culture producing pharmaceuticals, nutraceuticals and food ingredients," said Dr Franks.
The research, which is supported by a combination of public and private funds, was presented at a conference called Bio2002.