The Production of Aromas by Plant Cell Cultures

A.H. Scragg

Faculty of Applied Biology, University of the West of England, Frenchay, Bristol, BS16 1QY, UK

1 Introduction 240

2 Plant Cell Culture 241

2.1 Development of Plant Cell or Tissue Cultures 242

3 Potential Aroma Production by Plant Cell Culture 244

4 Accumulation of Aroma Components in Plant Cell Cultures 245

4.1 Complex Nature of Aromas 248

4.2 Volatility 250

4.3 Cytotoxicity of Essential Oils 251

4.4 Differentiation 252

4.5 Transformed Cultures 253

5 Process Development 254

5.1 Suspension Cultures 254

5.2 Organised Cultures 258

5.3 Provision of an External Accumulation Site 258

6 Conclusions 259

7 References 260

The adoption of a plant cell or tissue culture process for the production of various aroma compounds will depend on its ability to compete with current agricultural sources. To compete with the normal sources the plant culture process will, at least initially, involve low volume and high price compounds and high productivity, which requires a high yield of product. A wide range of aroma compounds have been detected in plant cultures, but the yields have been low (0.01-0.3% dry weight). Increases in yield have been obtained either by providing a site for the accumulation of the aroma compounds or by inducing some form of differentiation, such as root or shoots, into the culture. The scale-up of either suspension or organised cultures is possible as bioreactor cultivation of both types of culture has been successful, but there may be problems in obtaining high growth rates and biomass levels with organised cultures.

Advances in Biochemical Engineering/ Biotechnology, Vol. 55 Managing Editor: T. Scheper © Springer-Verlag Berlin Heidelberg 1997

1 Introduction

Higher plants are the source of many industrially important compounds. Plants serve as a source of industrial oils, flavours, fragrances, resins, gums, natural rubber, waxes, saponins and other surfactants, dyes, pharmaceuticals, pesticides, and other specialty products. Plants have been used for many years as a source of pharmaceuticals, starting perhaps in 1785 when William Withering reported the use of foxglove extracts to treat heart conditions [1]. However, due to advances in synthetic chemistry and the vast array of antibiotics produced by microorganisms the use of plant derived drugs has declined. Despite this trend some 25% of prescribed drugs are still extracted from plants [2], and with the recent interest in the ethnobotanical approach to new drug development, the targeting of plants used by native cultures as medicines [3,4], plant derived products are still of great value. A recent example of an important plant derived drug is taxol, which is used to treat a number of cancers, and was isolated from Taxus brevifolia, the Pacific pine.

Plants as a source of flavours and aromas should not be forgotten as the world market for flavours is worth between two and three billion dollars per annum [5], A great number of spices, condiments and beverages owe their characteristic properties of flavour and aroma to the secondary compounds that they contain. In many cases the flavour and aroma compounds were shown to be a very complex mixture which depends on the balance of the compounds to give the correct flavour or aroma. On the other hand, some flavours and aromas are due mainly to a single compound. The distinction between flavour and aroma is difficult, as when a flavour is volatile it becomes an aroma (Fig. 1).

The demand for aromas in the food and perfume industry, like that of the flavour industry, is increasing at a rate of 5-7% per annum. Some of the

Aromatherapy Natural Scents that Help and Heal

Aromatherapy Natural Scents that Help and Heal

You have probably heard the term Aromatherapy and wondered what exactly that funny word, „aromatherapy‟ actually means. It is the use of plant oils in there most essential form to promote both mental and physical well being. The use of the word aroma implies the process of inhaling the scents from these oils into your lungs for therapeutic benefit.

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