[show abstract][hide abstract] ABSTRACT: Sour citrus fruits of the various kinds are cultivated in Japan. Citrus junos (yuzu), Japanese typical sour citrus, have been treated as a raw material for juice processing. Most of the juice processing residue was disposed without being used despite contain valuable compounds. The parts of yuzu peel account for approximately 50% of whole fruit. It contains valuable hydrocarbon and carbohydrate such as essential oil and water soluble dietary fiber consisted of pectin. At first, supercritical carbon dioxide (SC-CO 2) was used as a solvent for extract the essential oil of yuzu peel. The effects of pressure and temperature on the yield of total oil extract were studied under the following conditions; pressures at 10-30 MPa, temperatures at 40-80 o C. The extract was divided into two layers. The yield of extract tended to increase with a pressure and temperature increase. The upper layer is an essential oil and the lower layer is moisture of peel. The highest recovery rate of essential oil was reached 95% at the temperature of 80 o C and pressure of 30MPa. In second step, sub-critical water was applied to extract pectin from residue of SC-CO 2 extraction. Experimental conditions were carried out under following conditions; pressures at 4-30 MPa, temperatures at 110-160C. The yield of extracted pectin was greater than 75% at a temperature range of 120-140C and pressure range of 4-30 MPa. The molecular weight of extracted pectin was tended to become small molecule along with increasing temperature. Furthermore, it was suggested that the elimination of methyl groups in the pectin molecule was enhanced the increase of the extraction temperature.
The 8th International Conference on Supercritical Fluids; 10/2013
[show abstract][hide abstract] ABSTRACT: To investigate the expressional control of branched respiratory chain complexes of the amino-acid producing bacterium Corynebacterium glutamicum according to growth conditions, the expression indexes of the ndh, sdh, qcrCAB, ctaCF, ctaD, ctaE, and cydAB genes were estimated under aerobic and microaerobic, and carbon-rich and -poor conditions. The promoter region of each target gene was cloned upstream of the EGFP gene on expression vector pVK6, and the nine reporter constructs were transformed into C. glutamicum ssp. lactofermentum. The cytochrome content of cellular membranes obtained from each growth phase closely corresponded to the expression indexes based on EGFP fluorescence and cell density, indicating that this rapid and convenient method is suitable for analyzing the expression levels of respiratory chain complexes. Using this method, we demonstrated that a reciprocal change in the expression levels of cytochrome bd-type and aa (3)-type oxidases occurs when C. glutamicum cells are held in stationary phase for extended periods.
Journal of Bioenergetics 06/2011; 43(3):257-66. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Background
Citrus sphaerocarpa Hort. ex Tanaka is one of many popular sour citruses in Japan. Its juice processing peel residues contain a lot of useful compounds including essential oil. Our interests mainly focused on the extraction of this essential oil using supercritical carbon dioxide (SC-CO2), an environmentally benign and generally regarded as safe solvent that has many advantages such as low critical temperature, low viscosity, and easy separation from the extract. In this research, essential oil was extracted from Citrus sphaerocarpa Tanaka peel using SC-CO2 at extraction temperatures of 313 to 353 K and pressures of 10 to 30 MPa.
A maximum yield of 1.55% (by weight of wet sample) was obtained at the temperature of 353 K and the pressure of 20 MPa. The yield obtained by SC-CO2 method was over 13 times higher than that of the conventional cold-press method. Extracted essential oil was qualitatively analyzed using GC/MS, identifying 49 compounds including several non-polar and weakly polar hydrocarbons such as terpenoid, free fatty acid, and coumarin. Compared to the extracts obtained by the conventional methods, the extracts by SC-CO2 had lower content of monoterpenes and higher content of oxygenated compounds, sesquiterpenes, which strongly contribute to the aromatic characteristics of the extracts. Auraptene, a bioactive compound was also identified in the SC-CO2 extract.
Kabosu essential oil with a fresh natural fragrance was effectively extracted using SC-CO2 compared to the conventional extraction method. In addition, it was found that the extract contained higher content of aromatic components that characterize Kabosu. This work provides an important sequential method for the recovery of valuable compounds from citrus fruit waste using an environmentally friendly technique.