Zinc accumulation and the growth of Saccharomyces cerevisiae were investigated in a culture with zinc sulfate-supplemented medium. The cultivations were performed on Sabouraud dextrose broth medium in aerobic conditions, without the addition of zinc (control culture) and with the addition of zinc sulfate (5, 10, 15, 30 and 60 mg ZnSO 4 l-1 medium) at 28°C for 72 hours. The results showed similar trends of yeast growth rates at 24, 48, and 72-hour interval, with concentrations above 10 mg l-1 ZnSO 4 in the nutritional medium significantly decreasing the yeast growth rate and the biomass yield (P<0.05). Substantial differences between the initial ZnSO 4 concentrations in the growth medium were demonstrated in the overall adsorption of Zn ions (Zn 2+) in yeast cells by a colorimetric assay (P<0.05). Similarly, the content of total accumulated zinc, as well as the fractions of Zn present in cells depended mainly on the zinc concentration in the medium, as the total Zn accumulation and organically bound Zn fractions were increased by elevating the ZnSO 4 supplementation in the culture medium up to 30 mg l-1 , but gradually reduced by any further addition of ZnSO 4 determined by an ICP-MASS assay (P<0.05). In the presence of 30 mg l-1 ZnSO 4 , the Zn content in the biomass increased by 24-fold, to 4132.34 mg g-1 in comparison to 171.9 mg g-1 achieved in the basal medium. Thus, the ability of S. cerevisiae to accumulate zinc can be used for production of a zinc-rich ingredient for functional food products.

The present experiment was conducted to investigate the effect of feeding different concentrations and the source of zinc (Zn) on the performance, tissue mineral status, superoxide dismutase (SOD) enzyme activity and meat quality in 0–4-week-old broiler chicks. Dietary treatments included the corn–soybean meal-based diet (control) and the basal diet supplemented with Zn at 20, 50 or 80 mg/kg, added as ZnSO4, Zn-methionine or Zn-enriched yeast. The results showed that birds fed Zn-supplemented diets had higher average weight gain and average feed intake than did birds fed the control diet (P < 0.01). At the end of the experiment, the Zn deposition in pancreas, liver and tibia increased (P < 0.01), regardless of the source, in response to increasing dietary Zn concentrations, whereas plasma Zn status was significantly increased by the highest Zn supplementation level. The main effect of Zn supplementation level was significant for the activities of Cu and/or Zn SOD in the liver and pancreas (P < 0.01). As broiler given 50 mg Zn had higher tissue SOD activity than did broilers fed the other treatment diets. Furthermore, Zn supplementation at up to 50 mg/kg significantly increased (P < 0.01) Zn accumulation and SOD activity and decreased lipid peroxidation in muscles around the femur bone. Results from the present study demonstrated that supplementation with 50 mg Zn may be sufficient for normal broiler growth to 28 days of age and the dietary inclusion of organic Zn could be utilised more effectively than that of inorganic sources.

This experiment was conducted to investigate the effect of feeding different concentrations and sources of zinc (Zn) on the growth performance, tissue mineral status, bone morphology and immunity responses in 0-4-week broiler chickens. Four hundred and forty 1-d-old broiler chickens were assigned randomly to 11 dietary treatments with 4 cages per treatment and 10 broiler chickens per cage in a completely randomized design. Dietary treatments were: corn-soybean meal basal diet (negative control), basal diet supplemented with 5 g yeast/kg (yeast), and basal diet supplemented with 20, 50, or 80 mg of added Zn/kg as ZnSO4, Zn-Met, or Zn-yeast in a 3 x 3 factorial arrangement of treatments. The results showed that broilers fed Zn supplemented diets had greater average weight gain and average feed intake than chickens fed the negative control diet (p<0.05). The Zn deposition in tibia, meat (thigh and breast) and excreta increased (p<0.01), regardless of source, in response to increasing dietary Zn concentrations. Zinc level increased dry weight of tibia bone and its large diameter. The strength of tibia bone as judged by Seedor index and breaking strength was improved (p<0.01) with Zn concentration in increased diets. Furthermore, supplemental Zn up to 50 mg/kg improved immunity responses of broiler chickens (p<0.01). It is concluded that supplementation with 50 mg Zn may be sufficient for normal broiler growth up to 28 d of age and the dietary inclusion of organic Zn could be utilized more effectively when compared to inorganic sources.