Selection of culture medium and conditions for the production of selenium enriched Saccharomyces cerevisiae

Abstract

Selenium (Se) yeast is a recognized source of organic food-form of Se and it plays a vital role in animal and human nutrition. The organic Se supplementation in the form of yeast has been shown to have beneficial effects on growth, immune status and reproduction in many animal species, thereby improving the productivity and economical benefits in livestock production. Subsequently, strategies to supplement animal feeds with Se yeast have led to the development of industrial production of Se yeast. The aim of the present study was to improve the yeast biomass production measured as dry cell weight (DCW) and Se enrichment of yeast cells through optimization of the culture conditions and culture media. The culture conditions were optimized by the shake flask experiments. Maximum cell density (2.93 g/LDCW) was observed at pH 5 to 5.5, at 30 °C (2.88 g/L DCW). Significantly higher DCW was recorded when glucose was used as the carbon source (3.09 g/L DCW). The media optimization study carried out in fermentors with five different media (defined medium–A, defined medium-B, synthetic medium, rich medium and industrial medium) showed that the synthetic medium yielded maximum yeast biomass (12.8 g/LDCW) followed by rich medium (11.7 g/L DCW) and defined medium B (10.5 g/LDCW). The Se accumulation was also significantly higher in synthetic medium (2718.3 ppm), followed by industrial medium (2457.7 ppm) and defined medium-B (2251.3 ppm). The methylene blue reduction time (MBRT) was very high ( >15 m) in synthetic medium indicating the highest accumulation of organically bound Se, and MBRT was moderate for defined medium-A and industrial medium ( <10 m).

Keywords: Saccharomyces cerevisiae, synthetic medium, carbon source, selenium enrichment, methylene blue reduction time (MBRT)

African Journal of Biotechnology Vol. 12(20), pp. 2972-2977