ISSN:
0006-3592
Keywords:
Saccharomyces cerevisiae
;
hepatitis B surface antigen (HBsAg)
;
continuous culture
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
We have studied the growth rate dependence of hepatitis B surface antigen (HBsAg) p24s monomer and lipoprotein particle synthesis produced in Saccharomyces cerevisiae using galactose-limited continuous culture. The hepatitis B virus S gene, which encodes the p24s monomer, is transcribed under the control of the GAL 10p on a chimeric 2-μm plasmid harbored in a haploid yeast strain. Monomers autonomously form lipoprotein aggregates (particles) in vivo using only host-cell-derived components. Steady states were evaluated in a range from 0.015 h-1 to washout (0.143 h-1). Both p24s monomer and HBsAg particle levels, at steady state, varied in an inverse linear manner with growth rate. A consistent excess of total p24s monomer to HBsAg particle, estimated at five- to tenfold by mass, was found at all dilution rates. The average copy number of the 2-μm plasmid (carrying LEU2 selection) remained constant at 200 copies per cell from washout to 0.035 h-1. Surprisingly, the average copy number was undetectable at the lowest dilution rate tested (0.015 h-1), even though HBsAg expression was maximal. Total p24s monomer and HBsAg particle values ranged twofold over this dilution rate range. No differences in the trends for HBsAg expression and average copy number could be detected past the critical dilution rate where aerobic fermentation of galactose and ethanol overflow were observed. HBsAg expression in continuous culture was stable for at least 40 generations at 0.100 h-1. © 1996 John Wiley & Sons, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
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