3 research outputs found
The exopolysaccharides biosynthesis by Candida yeast depends on carbon sources
Background: The exopolysaccharides (EPS) produced by yeast exhibit
physico-chemical and rheological properties, which are useful in the
production of food and in the cosmetic and pharmaceutical industries as
well. The effect was investigated of selected carbon sources on the
biosynthesis of EPS by Candida famata and Candida guilliermondii
strains originally isolated from kefirs. Results: The biomass yields
were dependent on carbon source (sucrose, maltose, lactose, glycerol,
sorbitol) and ranged from 4.13 to 7.15 g/L. The highest biomass yield
was reported for C. guilliermondii after cultivation on maltose. The
maximum specific productivity of EPS during cultivation on maltose was
0.505 and 0.321 for C. guilliermondii and C. famata, respectively. The
highest EPS yield was found for C. guilliermondii strain. The EPS
produced under these conditions contained 65.4% and 61.5%
carbohydrates, respectively. The specific growth rate (\u3bc) of C.
famata in medium containing EPS as a sole carbon source was 0.0068 h-1
and 0.0138 h-1 for C. guilliermondii strain. Conclusions: Themost
preferred carbon source in the synthesis of EPS for both Candida
strains was maltose, wherein C. guilliermondii strain showed the higher
yield of EPS biosynthesis. The carbon source affected the chemical
composition of the resulting EPS and the contribution of carbohydrate
in the precipitated preparation of polymers was higher during
supplementation of maltose as compared to sucrose. It was also found
that the EPS can be a source of carbon for the producing strains
Utilization of a waste glycerol fraction using and reusing immobilized Gluconobacter oxydans ATCC 621 cell extract
Background: Depletion of petroleum resources has enforced the search
for alternative sources of renewable energy. Introduction of biofuels
into the market was expected to become a solution to this
disadvantageous situation. Attempts to cover fuel demand have, however,
caused another severe problem\u2014the waste glycerol generated during
biodiesel production at a concentration of approximately 10% w/w. This,
in turn, prompted a global search for effective methods of valorization
of the waste fraction of glycerol. Results: Utilization of the waste
fraction at 48 h with an initial glycerol concentration of 30
g\ub7L-1 and proceeding with 62% efficiency enabled the production of
9 g\ub7L-1 dihydroxyacetone at 50% substrate consumption. The re-use
of the immobilized biocatalyst resulted in a similar concentration of
dihydroxyacetone (8.7 g\ub7L-1) in two-fold shorter time, with an
efficiency of 85% and lower substrate consumption (35%). Conclusions:
The method proposed in this work is based on the conversion of waste
glycerol to dihydroxyacetone in a reaction catalyzed by immobilized
Gluconobacter oxydans cell extract with glycerol dehydrogenase
activity, and it could be an effective way to convert waste glycerol
into a valuable product
Effect of initial pH of medium with potato wastewater and glycerol on protein, lipid and carotenoid biosynthesis by Rhodotorula glutinis
Background: Rhodotorula glutinis is capable of synthesizing numerous
valuable metabolites with extensive potential industrial usage. This
paper reports the effect of initial culture medium pH on growth and
protein, lipid, and carotenoid biosynthesis by R. glutinis. Results:
The highest biomass yield was obtained in media with pH 4.0\u20137.0,
and the value after 72 h was 17.2\u201319.4 gd.w./L. An initial pH of
the medium in the range of 4.0\u20137.0 has no significant effect on
the protein (38.5\u201341.3 g/100 gd.w.), lipid (10.2\u201312.7 g/100
gd.w.), or carotenoid (191.7\u2013202.9 \u3bcg/gd.w.) content in the
biomass or on the profile of synthesized fatty acids and carotenoids.
The whole pool of fatty acids was dominated by oleic
(48.1\u201353.4%), linoleic (21.4\u201325.1%), and palmitic acids
(13.0\u201315.8%). In these conditions, the yeast mainly synthesized
torulene (43.5\u201347.7%) and \u3b2-carotene (34.7\u201338.6%),
whereas the contribution of torularhodin was only 12.1\u201316.8%.
Cultivation in medium with initial pH 3.0 resulted in a reduction in
growth (13.0 gd.w./L) and total carotenoid (115.8 \u3bcg/gd.w.),
linoleic acid (11.5%), and torularhodin (4.5%) biosynthesis.
Conclusion: The different values of initial pH of the culture medium
with glycerol and deproteinized potato wastewater had a significant
effect on the growth and protein, lipid, and carotenoid biosynthesis by
R. glutinis