The effect of different concentrations of organic and inorganic zinc on the growth and zinc content in yeast (Saccharomyces cerevisiae)

In the aquaculture industry, yeasts like other microorganisms such as algae, play a major role. Yeasts can absorb minerals from their culture and is able to transfer nutritional materials to other organisms. In this study, the effect of three concentrations (2.5, 5 and 7.5 g L-1) of organic (zinc-threonine) and inorganic (zinc-sulfate) zinc in culture media on the growth and enrichment of Saccharomyces cerevisiae was investigated. One group was also selected as the control treatment (each with 3 repetitions). Yeast culture was performed under standard conditions in YEPD medium and in 1-liter flasks. The amount of yeast added in the culture media was 10 g L-1. Based on results, the most growth inhibitory of yeast was observed after adding 2.5 g L-1 of zinc threonine, and with increase in zinc amount in culture media, the growth rate increased but still significantly lower than zinc sulfate and control treatments. In the zinc sulfate groups, the growth inhibitory of yeast was observed after adding 7.5 g L-1 of zinc sulfate, but other treatments did not show significant difference with the control treatment. In this study, the highest zinc content (115.67 ± 4.65 mg g-1) in yeast was observed in the treatment 7.5 g L-1of zinc sulfate, which was significantly higher than other treatments (P<0.05). Consequently, zinc content of yeast in the zinc threonine group were lower than the zinc sulfate groups but in zinc threonine groups, the maximum zinc content (23.07 ± 1.14 mg g-1) was observed in the treatment 5 g L-1 of zinc threonine, which was significantly higher than other treatments of this group (P<0.05). Discussion and conclusion: The present study showed that yeast could be enriched with both forms of zinc, but zinc sulfate induces the least growth inhibitory in the yeast and also Zn content after enrichment was higher in zinc sulfate treatments than zinc-threonine treatments.