Showing papers by "Byung-Gee Kim published in 1996"

Optimization of environmental factors for the production and handling of recombinant retrovirus

Abstract: Certain steps from the production to infection of the amphotrophic retroviral vector, MFG-LacZ, were optimized and the factors that affect retroviral titers were analyzed. Retroviral vector titers were highest when the culture supernatant was harvested 3 days after the producer cells had reached confluence. About a 2-fold increase in vector production was achieved at 32°C compared to that at 37°C. Low serum concentrations had no significant effect on the titers of virus produced by the CRIP cell line. Retroviral vectors were stable at 4°C but very unstable at 37°C and were quite sensitive to freezing and thawing. About 30%–50% of viral infectivity was lost during the thawing step and the loss was not recovered by the addition of commonly used cryoprotectants. Increase in viral exposure time for infection to target NIH3T3 cells was linearly proportional to the retroviral titer for up to 15 h. In addition, using DEAE-dextran in place of polybrene as a polycation during infection enhanced infection efficiency about 3-fold. The retrovirus was robust to simple ultrafiltration and its titer could be easily concentrated 16-fold. Taken together, our data suggest that at least a 100-fold increase in titer can be achieved with simple optimization.

Effect of the hydration state of supports before lyophilization on subtilisin-A activity in organic media.

Abstract: Subtilisin-A was colyophilized with various types of support materials, such as Amberlite IRC-50, Celite545, chitosan, DEAE-cellulose, DOWEX-1, zeolite, glass bead, and polystyrene. The colyophilized enzyme was used for the optical resolution of racemic 1-phenylethylamine with 2,2,2-trifluoroethylbutyrate in 3-methyl-3-pentanol. The enzyme activity in organic media changed dramatically according to the hydration state of the support materials before lyophilization. This effect was especially marked with supports of high water capacity (aquaphilicity), such as chitosan and DEAE-cellulose. By hydrating these supports of high aquaphilicity prior to lyophilization, subtilisin-A activity in organic media increased ca. 4–8 times, depending upon the supports used. This result suggests that the hydration state of aquaphilic support materials for colyophilization is critical to determining enzyme activity in organic solvents. © 1996 John Wiley & Sons, Inc.

Clean Technology Option in Alcohol Fermentation Industry

Abstract: A zero-discharge system for an alcohol fermentation industry was developed by reusing distillery wastes (stillage) as a cooking water for the next fermentation after treating it with proper separation processes. Ultrafiltration with a ceramic membrane played a key role. When the permeate from ultrafiltration of stillage was recycled back to the cooking step, fermentation time was extended from 60 to 70-80 hours but average ethanol production yield (8.8%) was quite similar to that in conventional process (9.0%). This new process was confirmed to be operated stably at least up to 8 recycles. Energy cost of this new process was compared with that of the conventional one and found to be more profitable. This new clean technology made it possible to eliminate the conventional biological treatment processes such as anaerobic digestion and activated sludge currently being operated in this type of industry.