Figure captions
Fig. 1A. Biosynthetic pathway of β-carotene from glucose and
xylose in engineered S. cerevisiae . A heterogolous xylose
assimilation pathway containing xylose reductase (XR), xylitol
dehydrogenase (XDH) and xylulokinase (XK) is connected with lower
glycolytic pathway by pentose phosphate pathway (PPP). Pyruvate is
produced from glucose and xylose and converted into cytosolic
acetyl-CoA. Yeast synthesizes farnesyl pyrophosphate from cytosolic
acetyl-CoA through the mevalonate pathway (MVA), as the common precursor
for the biosynthesis of ergosterol and heterogolous β-carotene. HMG-CoA
reductase (HMGR) is a key rate limiting enzyme in MVA. Cytosolic
acetyl-CoA is also the precursor for yeast lipids synthesis. G6P,
glucose-6-phosphate; F6P, fructose-6-phosphate; GAP,
glyceraldegyde-3-phosphate; X5P, xyllulose-5-phosphate; IPP, isopentenyl
pyrophosphate; DMAPP, dimethylallyl pyrophosphate; GPP, geranyl
pyrophosphate; FPP, farnesyl pyrophosphate; GGPP, geranylgeranyl
pyrophosphate. Fig. 1B. Pictures of glucose and xylose cultures
of SR8B strain at 30 hour. Fig. 1C. Transcriptional levels of
the genes related to the production of β-carotene in engineered S.
cerevisiae SR8B on glucose and xylose. Samples were taken at exponetial
phase from each condition for RNA extraction and expression level
analysis. Fold changes were calculated by dividing genes expression
levels on xylose by those on glucose. Three biological replicates and
three technical replicates were performed for each gene, and the error
bars represented standard deviations.
Fig. 2. The overlaid HPLC chromatograms of carotenoids
extracted from the engineered S. cerevisiae SR8B cultured on
glucose and xylose condition. Cells were cultured in a defined medium
containing either 40 g/L glucose or 40 g/L xylose from initial
OD600 1. Same amount of cells were harvested at 90 hour
from each condition to extract the carotenoids for HPLC chromotography.
Fig. 3. Batch fermentation profiles of the engineered S.
cerevisiae SR8B on glucose (A) and xylose (B) conditions and the
corresponding β-carotene production patterns on glucose (C) and xylose
(D). Data are presented as mean values and standard deviations of three
independent biological replicates.
Fig. 4 . Comparison of β-carotene production by the engineered
SR8B and SR8BH strains through glucose and xylose utilization. Cells
were harvested at the end of fermentation for β-carotene extraction and
quantification. Data are presented as mean values and standard
deviations of three independent biological replicates
Fig. 5A . Ergosterol production by the engineered SR8B strain
through glucose and xylose utilization. Cells were harvested at the end
of fermentation for ergosterol extractiona and quantification. Data are
presented as mean values and standard deviations of three independent
biological replicates. Fig. 5B. Lipid bodies visualization of
the engineered SR8B cells cultured in glucose and xylose condition.
Cells were harvested at exponential phase and stained with Nile Red
fluorescent dye. The stained cells were then viewd under a confocal
microscope with 63× oil immersion objective at 633 nm.
Fig. 6 Xylose feb-batch fermentation of the SR8B strain in a
3-litter bioreactor. The bioreactor picture on the right was taken at 80
h.