StatusThe thesis was presented on the 16 December, 2005
Approved by NCAA on the 26 January, 2006
Abstract– 0.35 Mb / in romanian
This work is dedicated to scientific and applied research in the fields of directed synthesis of carotinoids by yeasts and to estimation of the perspectives of their use. It consists of experimental research on the biosynthesis of carotinoids by the yeasts of genus Rhodotorula, cultivated on various nutrient media, and of obtaining preparations for aquaculture.
The yeast strain Rhodotorula gracilis CNMN-YS-03 with the most productive carotinoid biosynthesis (8841,989 mkg/l) was selected as a result of screening the strains with the ability to synthesize carotinoids.
Nonconventional nutrient sources (extracts from grape, apple and tomato waste products), precursors (sodium acetate, zinc acetate and citric acid), inductors of carotinoid biosynthesis (sunflower, olive, corn and soya oils, retinol) and coordination complexes ([Fe2Mn(CCl3COO)6(CH3OH)3], [Fe2NiO(CCl3COO)6(CH3OH)3]) were used for development of procedures for the directed carotinoid biosynthesis and yeast productivity stimulation.
Nutrient media that most effectively stimulated the biosynthesis of all carotinoid pigments, β-carotin, toruline and torularodine were obtained by using the methods of mathematical planning of experiments.
The nutrient medium that was rich with organic compounds and had additions citric acid, extracts from tomato waste products and [Fe2Mn(CCl3COO)6(CH3OH)3] permitted to increase the total content of carotinoids up to 15213,66 mkg/l.
Another medium for cultivation of pigment yeasts that had the same nutritive basis plus additions of tomato extract and citric acid increased the biosynthesis of β-carotin up to 4056,200 mkg/l. Presence in nutrient medium of corn oil increased the content of the toruline pigment up to 7208,291 mkg/l.
Cultivation of pigment yeasts in the organic medium that includes corn oil and citric acid stimulated the synthesis of torularodine in the yeast biomass up to 2730,496 mkg/l.
A nutritive medium that consisted of the tomato extract, corn oil and [Zn (Gly) (DL-Ser)] was developed for obtaining the biomass of the yeasts of genus Rhodotorula with predictable zinc content. This medium permitted to obtain up to 16,31 g/l of the biomass of carotinoid synthesizing yeasts containing 1,87 mg% of zinc.
Technologies and schemes were elaborated for obtaining two preparations for stimulation of the development of caviar and larvae and for starting fish forage. They are based on exometabolites and Zn enriched biomass of yeasts of genus Rhodotorula with ability for carotinoid synthesis.
The obtained results permit to include the red yeast Rhodotorula gracilis CNMN-YS-03 into the list of the perspective objects of biotechnology that can be used for production of carotinoid pigment and development of biopreparations with a wide spectrum of application.