S-Space College of Agriculture and Life Sciences (농업생명과학대학) Dept. of Food and Animal Biotechnology (식품·동물생명공학부) Theses (Master's Degree_식품·동물생명공학부)
Microbial engineering analysis of xylitol production by recombinant Saccharomyces cerevisiae
- Issue Date
- 서울대학교 대학원
- 세포 재순환; cell recycle; 새포 생육력; cell viability; 발효; fermentation; flow cytometry 분석법; flow cytometry; HAP4; 재조합 S. cerevisiae; recombinant Saccharomyces cerevisiae; 자일리톨; xylitol
- Thesis(master`s)--서울대학교 대학원 :농생명공학부,2004.
- Xylitol is a well-known five-carbon sugar alcohol with low-calorie and anticariogenic
characteristics. It has been used as a sugar substitute in the food
industry due to various functional properties.
This thesis was concerned with analysis of effects of fermentation strategies
and HAP4 gene expression on xylitol production by recombinant Saccharomyces
cerevisiae harboring the xylose reductase gene from Pichia stipitis.
Various fermentation strategies including batch, fed-batch, repeated fed-batch
and fed-batch with cell recycle were tested to increase the yield and rate of
xylitol bioconversion from xylose using recombinant Saccharomyces cerevisiae
BJ3505:¥äXR. Among them, the fed-batch fermentation with cell recycle was chosen
as the most effective fermentation process. Yeast extract was found to be the
best nitrogen source for xylitol production and cell viability. The fed-batch
fermentation with cell recycle and addition of yeast extract resulted in 2
g/L?hr xylitol productivity and 121 g/L xylitol concentration which are 2 and 5
times higher than the corresponding values of the batch fermentation.
As the fraction of viable cells generally plays an important role in
bioconversion processes, flow cytometry was used to measure cell viability in a
fast and accurate manner. Flow cytometric analysis of the recombinant yeast
cells stained with propidium iodide exhibited that cell viability was maintained
over 95% throughout the fermentation.
The HAP4 gene encoding a transcriptional activator in the respiratory metabolism
was overexpressed in S. cerevisiae BJ3505:¥äXR to investigate its effects on
xylitol production. In batch fermentation, overexpression of the HAP4 gene in S.
cerevisiae BJ3505:¥äXR increased dry cell mass slightly without affecting the
performance of xylitol production.
- Files in This Item: There are no files associated with this item.