Biosynthetic Production of Carotenoids Using Yeast Strains of Genus Rhodotorula on the Cheap Beer Wort Substrate

Abstract

Carotenoids having primary significance for animal husbandry, medicine and food industry are objects of studies to optimize their production conditions and to establish their complex role in living systems. Synthesis of carotenoids by microorganisms is preferential for industrial use due to their natural origin and possibility of combining production with waste disposal. Native microbial strains are the basis for selecting superproducers of organic pigments. In this study, the red yeasts of Rhodotorula genus were incubated in beer wort medium at initial cultural parameters (sugar concentration 6 degrees Balling, temperature 26°C, stirring rate 200 rpm, 4 days of fermentation). Analysis of biomass and carotenoid production by Rhodotorula yeast was performed under defined conditions. Two strains of R. glutinis BIM Y-253 and BIM Y-158 synthesizing over 100 µg carotenoids per 1 g biomass, the mark corresponding to the average level of production, were selected. The concentration of carotenoids generated by strain R. glutinis BIM Y-253 in the nutrient medium exceeded 1 mg / l. Screening of red yeast for the types of synthesized carotenoids showed predominance of torulene- and torularhodin-like compounds in isolated total pigment fractions. At the following experimental stage the effect of organic supplements on production of biomass and carotenoids by the selected strain R. glutinis BIM Y-253 was studied. Yeast incubation with 0.05% malic acid – the substrate for final reaction of TCA cycle, and fine grinding of biomass resulted in average carotenoid yield 3,5 mg/l. Our findings demonstrate the potential carotenoid productivity of red yeast at the initial values of incubation parameters, and illustrate the impact of organic compounds on biosynthetic efficiency of native yeast culture.