THE EFFECT OF ZnSO4 IN THE CULTIVATION MEDIUM ON RHODOTORULA GLUTINIS CCY 020-002-033 YEAST BIOMASS GROWTH, β-CAROTENE PRODUCTION AND ZINC ACCUMULATION

Abstract

The goal of this work was to evaluate the effect of zinc sulphate heptahydrate on growth rate and β-carotene production and to obtain zinc-enriched biomass using selected yeast strain Rhodotorula glutinis CCY 020-002-033. The batch cultivation was performed on synthetic basal medium supplemented with various concentrations of ZnSO4·7H20 (0.025%, 0.035%, and 0.050%), in shake flasks and aerobic conditions, at 300C, for five days. Total zinc accumulated in yeast cells after fermentation period was performed using ICP-OES. The identification and yield of β–carotene were investigated by chromatographic analysis (HPLC). It was found that the amount of total zinc accumulated in yeast cells depends mainly on the zinc concentration in the culture medium. The highest zinc content of 7.030 mg/g dry biomass was obtained at optimal concentration of 0.025%, with an incorporation efficiency of 87%. High concentration of 0.050% was not tolerated by yeast. Zinc salt in concentration of 0.025%, acted as stimulant for volumetric β–carotene but not improve yeast growth biomass. β-Carotene maximum content in this strain’s cell mass accounted 7.1 mg/L, when the dry cell biomass (1.89 g/L) was smaller than control (1.94 g/L), although there was no significant difference observed in final dry cell biomass versus control. The obtained results showed that when ZnSO4·7H20 concentration was increased up to 0.050% a decrease in yeast growth rate, β–carotene production and zinc accumulation was observed.