| dc.description.abstract | Carotenoids sources include plants, algae, and photosynthetic bacteria. A novel
bacterium Paracoccus sp BOG 006 T which was isolated from the outflow of Lake
Bogoria hot spring has also been identified to secrete carotenoids.
The main objective of the study was to optimize conditions for biomass
production and to quantify the carotenoids secreted by Paracoccus sp BOG 006T
. The
effects of pH, NaCl concentration, temperature, carbonate addition and acetate addition
on the cell biomass production were studied. This was followed by a study of the effect
of optimized growth media on cell biomass and carotenoids production. The effect of
solvent; acetone, hexane: ethyl acetate 1:1, acetone: hexane 2:1 and dichloromethane:
methanol 4:1, and condition variation on the carotenoid extraction process was also
investigated.
The total carotenoids content was quantitatively evaluated spectrophotometrically
and qualitatively using open column chromatography, thin layer chromatography and
high pressure liquid chromatography.
The set of conditions stimulating the highest biomass growth were identified as:
;
pH 9.0, 1% NaCI at 37°C. Paracoccus sp BOG 006T had a higher growth rate in Beef
Infusion (BI) than in Luria Bertani (LB) medium. The cell biomass was 67.3% higher in
BI medium compared to the optimized LB medium (LBopt medium). Total carotenoids
and astaxanthin recovered from LBopt medium was 3719.7 ug/g and 413 ug/g
respectively. Hence higher carotenoid yields were obtained from cells grown in LB
medium than from the BI medium which gave a lower yield of 2087.7 ug/g and 231.8
ug/g total carotenoids and astaxanthin respectively.
xu
Total carotenoids recovered were highest in acetone. Extraction was found to
improve with the increase in extraction time and centrifuge rotation speed. Extraction for
10 min was observed to achieve a better recovery than extraction for 5 min. Recovery
was higher at 6000 rpm than at 4000 rpm. The highest carotenoid recovery was 3745.7
ug/g when using acetone at 6000 rpm for 10 min. The main carotenoids identified were
lutein, ~-carotene and astaxanthin.
Paracoccus sp BOG 006T tolerated high pH of up to 10.0 and was capable of
growth at relatively high temperatures of up to 45°C. This lowers its susceptibility to
contamination, and indicates a good possibility for Paracoccus sp BOG 006 T application
in industrial production of carotenoids. Since total carotenoids production was observed
to be higher in LB medium, a sub-optimal medium for Paracoccus sp BOG 006T growth,
it was deduced that stress favours higher yields of carotenoids in p,aracoccus sp BOG
006T
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