Storage organ of Dioscorea opposita was efficiently generated by using a drum type bioreactor. This reactor was not equipped with a system for mechanical aeration and explants were immersed intermittently into the medium on rotation. When explants precultured on a rotary shaker were transferred to the bioreactor, approx. 230 pieces of storable organs that could be bulbils or microtubers were generated after 5 weeks. These organs sprouted within a week and eventually grew intonormal plants.
Bryophytes, or mosses, are considered the most maintenance-free materials for roof greening. Racomitrium species are most often used due to their high tolerance to desiccation. Because they grow slowly, a technology for forcing their growth is desired. We succeeded in the efficient production of R. japonicum in liquid culture. The structure of the microbial community is crucial to stabilize the culture. A culture-independent technique revealed that the cultures contain methylotrophic bacteria. Using yeast cells that fluoresce in the presence of methanol, methanol emission from the moss was confirmed, suggesting that it is an important carbon and energy source for the bacteria. We isolated Methylobacterium species from the liquid culture and studied their characteristics. The isolates were able to strongly promote the growth of some mosses including R. japonicum and seed plants, but the plant-microbe combination was important, since growth promotion was not uniform across species. One of the isolates, strain 22A, was cultivated with R. japonicum in liquid culture and in a field experiment, resulting in strong growth promotion. Mutualistic symbiosis can thus be utilized for industrial moss production.
A chitosan-inducive class III peroxidase (Prx34) found in Physcomitrium patens was produced in an Escherichia coli system. Recombinant Prx34 (rPrx34) was not expressed in inclusion bodies but in a soluble form. Purified rPrx34 showed over 20-fold higher specific activity toward diammonium 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) than commercially available horseradish peroxidase (HRP). rPrx34 displayed high catalytic efficiency compared with HRP with a 10-fold higher efficiency toward ABTS and a 3-fold higher efficiency toward tetramethylbenzidine. However, the catalytic efficiency of rPrx34 toward o-phenylenediamine was 50% lower than that of HRP. In addition, the catalytic efficiency against H2O2 was higher under all substrate oxidation conditions examined. The thermal stability of rPrx34 is 30–40 °C which is the same as HRP; however, approximately 10% of the activity remained after recovering from 100 °C treatment. Activity was maintained after being exposed to a pH range of 2–12 over 16 h. These results indicate that rPrx34 is suitable for applications in various fields.
Formaldehyde (HCHO) is an air pollutant suspected of being carcinogenic and a cause of sick-house syndrome. Microorganisms called methylotrophs, which can utilize reduced C(1) compounds such as methane and methanol, fix and assimilate HCHO, whereas most plants are unable to assimilate HCHO directly. We found that a bacterial formaldehyde-fixing pathway (ribulose monophosphate pathway) can be integrated as a bypass to the Calvin-Benson cycle in transgenic Arabidopsis thaliana and tobacco by genetic engineering. These plants showed enhanced tolerance to HCHO and enhanced capacity to eliminate gaseous HCHO by fixing it as a sugar phosphate. Our results provide a novel strategy for phytoremediation of HCHO pollution, and also represent the first step toward the production of plants that can assimilate natural gas-derived C(1) compounds.
The resting period and field performance of potato (Solanum tuberosum L.) tubers derived from a jar fermentor culture were investigated. About 40% (w/w) of the tubers easily lost more than 40% (w/w) of their weight during the first week after being removed from the jar fermentor and stored under room conditions. Sprouting of such easily wilting tubers was clearly delayed whereas other tubers sprouted within 3 months under the same conditions. When the tubers were transplanted and cultivated under field conditions, a yield decrease was observed with the late sprouting tubers. This suggested that the tubers could be selected according to the decrease in their weight after culture.
