With its high protein, vitamin and mineral content, Spirulina platensis (SP) is the most widely used microalgae as a food supplement and the most cultivated microalgae for this purpose. Zinc is a regulatory microelement that is incorporated into the structure of many proteins in the cell and is particularly deficient in cereal-based societies. Due to the high adaptability of SP to environments with high metal concentrations and its high capacity to secrete substances called phytochelatin and metal-binding capacity, in this study zinc-enriched SP (ZnSP) was produced by binding metals to SP by organic means. For this purpose, modified media with 4 different Zn concentrations were prepared and SP was cultured in these media. Optical density, chlorophyll-a, phycobiliprotein and dry cell weight analyses were performed to monitor the culture. During the culture period, biomass and filtered culture medium were collected from logarithmic and stationary stages and Zn analyses were performed. The most suitable culture medium and growth conditions were determined to obtain Zn-enriched SP. 338.4 mg kg-1 Zn was measured in SP biomass grown in Zn-3 medium containing 8 mg L-1 Zn. It may be possible to obtain Zn-enriched SP in this medium and under the specified culture conditions, and even this ratio can be increased by adding Zn to the culture medium after the logarithmic stage.

In this study was carried out to determine the effects of humic acid in heavy metal stress of lettuce changes in some of the morphological and physiological characteristics. In studies conducted in controlled greenhouse conditions, lettuce plants subjected to four different 4 different humic acid levels humic acid doses (0, 2, 4, 8 L/da) and 4 different heavy metal irrigation levels (Control: 0 ppm; I. mixture: 0.2 ppm Cu + 0.01 ppm Cd + 5 ppm Pb + 2 ppm Zn; II. mixture: : 0.4 ppm Cu + 0.02 ppm Cd + 10 ppm Pb + 4 ppm Zn; III. mixture: 0.8 ppm Cu + 0.04 ppm Cd + 20 ppm Pb + 8 ppm Zn). Four weeks after at heavy metal and humic acid treatment young plants were harvested and the shoot fresh and dry weight, root fresh and dry weight, shoot and root length, and leaf areas, MDA, superoxyde dismutase (SOD) and glutathione reductase (GR) were determined. The most highly toxic effects were determinate III. mixture level (0.8 ppm Cu + 0.04 ppm Cd + 20 ppm Pb + 8 ppm Zn). MDA and antioxidative enzyme activities increased in plants irrigated with water containing a mixture of heavy metal. Humic acid applications had a positive effect on reducing of the limiting effect of heavy metal stress on growth and development.