Submitted to: Journal of Herbs, Spices and Medicinal Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 1998
Publication Date: N/A
Interpretive Summary: Carbon dioxide (CO2) is a major coproduct generated in alcohol fermentation. For every gallon of ethanol produced, an equal amount of carbon dioxide is made. In this study, the possibility of employing this excess CO2 to enhance growth of various mint species under high or ultra-high CO2 levels was evaluated. Ultra-high CO2 levels (>10,000 ppm CO2) were found to give optimum growth of these plants. For example, growth rates (i.e., fresh weights) can be accelerated up to 32X in spearmint, and similar fold increases were obtained with lemon basil, oregano, peppermint, and thyme. In addition, root, shoot, and leaf production was greatly enhanced by employment of ultra-high CO2 levels. This information will benefit the commercial tissue culture/nursery industry by accelerating the growth of plants and will aid the ethanol industry by finding a high-value use for a current low-value coproduct generated during the fermentation process.
Technical Abstract: The growth of five species of Labiatae: lemon basil (Ocimum basilicum L.), oregano (Origanum vulgare L.), peppermint (Mentha piperita L.), spearmint (Mentha spicata L.), and thyme (Thymus vulgaris L.) shoots on MS medium (BM) containing 0 or 3% sucrose were studied under 350, 1,500, 3,000, 10,000, and 30,000 uL liter**-1 CO2. Greater CO2 levels, especially the ultra-high levels (i.e., >3,000 uL liter**-1 CO2), substantially increased fresh weight, shoot number, leaf number, and root number from Labiatae shoot cultures whether BM contained sucrose or not compared to the growth obtained from cultures grown under the normal, atmospheric CO2 levels (350 uL liter**-1 CO2). For example, plantlet fresh weights, number of roots, number of axillary shoots, and number of leaves from spearmint cultures grown on BM containing 0 or 3% sucrose supplemented with 10,000 uL liter**-1 CO2 increased 35.2- and 3.3-, 11.7- and 6.8-, 21- and 9.5-, and 18.8- and 6.8-folds, respectively, when compared to growth of spearmint shoots grown on the same media without any CO2 enrichment. Similar fold increases for these same growth responses were also obtained with lemon basil, oregano, peppermint, and thyme shoots grown under atmospheres enriched with ultra-high CO2 levels (e.g., >3000 uL liter**-1 CO2). CO2 concentration, for best growth responses for all the Labiatae species tested, was 10,000 uL liter**-1 CO2.