Yadav and Prabha

owing to a continued consumer pressure to ‘go natural’. (Dowman, 2000).

Carotenoids are the most wide spread naturally occurring yellow, orange

and red pigments. The abundance of carotenoids in nature is probably

due to their relatively simple biosynthetic pathway, which has been

demonstrated in higher plants and algae but also in bacteria and yeasts. For

microbialcarotenoidsthereareatleastthreeimportantreasonsofanalyzing

theȱentireȱspectrumȱandȱtheȱcorrectȱamount:ȱfirstly,ȱmicroorganismsȱofferȱ

economical biotechnological production of carotenoids and provide an

alternative to chemical synthesis. In bacteria and in yeast, carotenoids

have been considered as typical secondary metabolites, playing a certain

roleȱinȱtheȱsurvivalȱofȱtheȱfittest microorganisms. Industrially, carotenoid

pigmentsȱareȱutilizedȱasȱfoodȱcolourantsȱandȱfeedȱsupplementsȱinȱfishȱandȱ

poultry (Frengova et al., 2003).

Recentlyȱcarotenoidsȱhaveȱattractedȱgreaterȱattentionȱdueȱtoȱtheirȱbeneficialȱ

effectȱonȱhumanȱhealthȱsuchȱasȱinvolvementȱinȱcancerȱprevention,ȱreductionȱ

of the risk for degenerative diseases such as cardiovascular diseases,

macular degeneration and cataract and enhancement of immune response.

(Costa et al., 2005; Iriani et al. , 2005). Thus, a comprehensive screening of

the microbial carotenoid spectrum could help to identify novel compounds

providingȱbeneficialȱeffects.ȱ

Rhodotorula is a carotenoid biosynthetic yeast, part of the Basidiomycota

phylum,ȱ easilyȱ identifiableȱ byȱ distinctiveȱ yellow,ȱ orange/redȱ coloniesȱ

(Postgate,ȱ 1994).ȱ Theȱ mainȱ carotenoidsȱ producedȱ wereȱ identifiedȱ asȱ

torularhodin,ȱtorulene,ȱγ-carotene,ȱandȱminuteȱβ-caroteneȱinȱRhodotorulaȱ

species.

Latha (2005) found that the Rhodotorula glutinis DFR-PDY which was able

to grow and form pigments under a wide range of initial pH conditions

from 2.5 to 9.5. The cell dry weight increased gradually with an increase

inȱtheȱpHȱofȱtheȱmodifiedȱCzapekȱdoxȱbroth;ȱwhileȱtheȱhighestȱcarotenoidȱ

yield (3.3mg/L) was obtained at pH 5.5 and can be considered as the

optimum pH for pigment production.

Theȱ specificȱ growthȱ rateȱ ofȱ theȱ Rhodotorula glutinis increased notably

with raise in temperature up to 30°C and lessened sharply above 30°C

due to the denaturation of the enzyme system of microorganism at higher

temperatures.ȱ Theȱ highestȱ specificȱ growthȱ rateȱ ofȱ yeastȱ wasȱ 0.238ȱ h−1ȱ

at 30°C (Aksu, 2007). In the present study the extracted pigment from

Rhodotorula minuta was subjected to pH and temperature stability.

106