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Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 20115. Influence of cultivation timeSeveral experiments were realized to determine the influence of the cultivation time, inthe range 1 – 6 days, on the yeast growth and both – total carotenoids and torularhodinformation were measured. The stationary phase characterized by an important production ofcarotenoid pigments starts after 48 hours in all cases.The total carotenoids concentration and the torularhodin concentration were determinedbased on the spectrometric recording of the extracts on the UV-VIS spectrophotometer(Jenway Spectrophotometer).The total carotenoids concentration was determined as β-carotene content by using theextract absorbance values (fig. 6); similar the torularhodin concentration was calculatedusing methanol extracts absorbance values (fig. 7) with the specific absorption coefficient,E 1% 1932.102Fig. 6. Absorption spectra of hexane extract for the Rhodotorula rubra ICCF 209 culture in MS3Until 48 h the ratio between the torularhodin concentration and the total carotenoidsconcentration is small, so the yeast biosynthesizes more the other pigments; then during thegrowth stationary phase the concentration of torularhodin can represent so far 90% fromtotal carotenoids content. The carotenoids concentration increases until 96-120 h, but afterthis duration the trend is towards the diminution of any carotenoids content.
Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011Fig. 7 Absorption spectra of methanol extracts for the Rhodotorula rubra ICCF 209 culture in MS34. CONCLUSIONSCulture media have a considerable influence on the yeast biomass accumulation andcarotenoid pigments biosynthesis, particularly torularhodin, component with a high-levelantioxidant potential.For all carbon sources tested the Rhodotorula rubra ICCF 209 strain presented a goodgrowth as can be seen from the OD 600 nm values. The yeast strain growth is stimulated byglucose, fructose, sucrose and maltose, but inhibited by lactose.The studied characteristics – yeast growth, the total carotenoids formation, and thetorularhodin formation recommend the initial pH range of 6-7 as being favorable, thetorularhodin ratio from the total carotenoids content being greater for the pH of 7.At the same time an inoculum concentration of 1-2 % is favorable for both yeast growthand carotenoids formation.When NH 4 NO 3 is replaced in the control medium with other mineral nitrogen sources(NH 4 H 2 PO 4 , (NH 4 ) 2 SO 4 , or NH 4 Cl) both the growth and the carotenoids formation arehigher when acid ammonium phosphate was used; in this case a fraction of about 95 %torularhodin is formed in the pigments mixture.103
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