Biomedical subjects

George T Tsao

Publications and source records attributed to George T Tsao.

4 recordsLinked to original sources

PubMed2003

Effects of pressure pulsation on oxygen transfer rate measured by sulfite method.

Pressure pulsation (PP) was investigated for its effects on oxygen transfer rate (OTR) measured by sulfite oxidation. By manipulating airflow rate, 0.41- 1.2 vvm, and a control valve in a 4-L bioreactor, the frequency of PP was varied at different gas pressures3-15 psig. A mathematical model of OTR was built and compared to experimental data. OTR was also examined at constant gas pressure, 4.5-15.0 psig. The results indicate a good agreement between measurement and model prediction. OTR above 9 psig during PP showed significant enhancement at 25 degrees C. This proves that PP not only affects the elevation of DO level, but also increases the interfacial area and mass transfer coefficient.

Aerobiosis↗

PubMed2002

Enhancement of oxygen transfer by pressure pulsation in aqueous glycerol fermentation.

Aeration plays an important role in the production of glycerol by fermentation with yeast. Effective aeration depends on a number of factors, such as amount of air, fineness of air dispersion, rate of agitation, and time of gas-liquid contact. This investigation dealt with the effect of periodic variation in gas pressure on oxygen transfer measured by sulfite oxidation and glycerol fermentation in stirred tanks. The oxygen transfer rate measured with the sulfite oxidation method was improved by 20-30% under the condition of pressure pulsation (PP) at 30 degrees C. The yield and productivity of glycerol were increased by about 26 and 6.8%, respectively, in 48 h by employing a glucose concentration of 250 g/L with PP at 30 degrees C.

Aerobiosis↗

PubMed2002

Pressure pulsation in solid-phase fermentation.

Inadequate dissipation of heat generated by biologic activities has prevented the use of solid-phase fermentation in large-scale applications. This study deals with the cooling effects of pressure pulsation on solid, porous beds. Pressure pulsation also enhances evaporation of medium moisture, which is also described. Computer software has been developed for on-line control of heat accumulation and moisture loss involving automatic variation in pressure pulsation frequency and airflow direction as well as replenishment of water. Aspergillus niger NRRL3 was cultivated on a moist, solid medium made of wheat bran and ground corncobs to produce cellobiase. During 100 h of fermentation, the maximum temperature inside the solid bed was kept under 40 degrees C, and the medium water content was successfully maintained between 61 and 65%, which was optimal for cell growth. Cells grew heavily on the solid-phase substrate and distributed uniformly. With good on-line control of temperature and moisture, the 12-L fermentor provided a better environment for enzyme production than 250 mL flasks did.

Aspergillus niger↗

PubMed2002

Production of 1,3-propanediol by Klebsiella pneumoniae.

1,3-Propanediol (1,3-PD) has numerous applications from polymers to cosmetics, foods, lubricants, and medicines. Recently, there are strong industrial interests in a new kind of polyester, polytrimethylene terephthalate, with 1,3-PD as a monomer. This new polyester shows significant promise for use in carpeting and textiles. In this article we introduce a mild aerobic fermentation process using a strain screened from Klebsiella pneumoniae ATCC 25955, which is insensitive to oxygen, to produce 1,3-PD. We also describe a two-step fermentation process starting with glucose that was converted into glycerol with a glycerol-producing yeast, followed by K. pneumoniae that converts glycerol into 1,3-PD without intermediate isolation and purification of glycerol.

Aerobiosis↗