Effects of ultrasound on cell growth and secondary metabolite production in plant cell cultures.

摘要

This project is aimed to study a new measure, the application of low-energy ultrasound (US), for the stimulation of secondary metabolite production in plant cell cultures.; The main objectives of the project are to gain better knowledge and understanding of the bioeffects of low-intensity US on plant cells and to explore the beneficial effects of US for secondary metabolite production in plant cell cultures. Three types of plant cell culture with tremendous commercial potential were used in this project, including Panax ginseng (producing saponins), Lithospermum erythrorhizon (producing shikonins) and Taxus chinensis (producing taxol). Suspension cultures of the plant cells were exposed to US in an ultrasonic bath at various US powers (maximum 82 mW/cm3) and exposure periods (maximum 8 min).; A number of novel and interesting effects of US on cell growth, viability and metabolism were found and the most remarkable effect was the promotion of secondary metabolite production. Under suitable exposure conditions, US increased the yields of secondary metabolites significantly, e.g., up to 60–70% increase in the saponin yield of P. ginseng cells and the shikonin yield of L. erythrorhizon, and up to 3-fold increase in the taxol yield of T. chinensis. The growth and viability of cells were usually depressed immediately after the exposure to US, but recovered gradually to levels similar to those of a normal culture in a few days, with virtually no net loss of biomass yield at the end of the culture period. The effects of US on the yield of secondary metabolites and cell viability showed a significant correlation with the total US energy applied.; Further analysis of the sonicated plant cells showed that the US exposure stimulated the activities of some key enzymes related to plant secondary metabolism such as phenylalanine ammonia-lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO). The enhancement of plant cell secondary metabolism by US appears to be a result of US-induced defense response of the plant cells.; In conclusion, US was found to be a simple and effective stimulus for secondary metabolite production in plant cell cultures. The effects of US on plant cell growth and metabolism are mostly attributed to the mechanical stress created by the vibrating US in the culture media. The enhancement of secondary metabolite synthesis may be a result of US-induced plant cell defense metabolism. The results and findings from this project make new contributions to the development of plant cell culture technology for the production of valuable plant secondary metabolites and to fundamental understanding of the bioeffects of US. (Abstract shortened by UMI.)