Growth exhibition and metallothioneins induction of Chlorella sp. exposed to different zinc salts

The exhibition of growth and the induction of metallothioneins of Chlorella sp. exposed to different kinds of zinc salts were investigated. The biomass, heat-stable proteins and Zn-MTs were measured when the Chlorella sp. were exposed to four kinds of Zn²⁺ (including zinc chloride, zinc acetate, zinc gluconate, zinc citrate) at the concentrations of 5, 10, 20, 50 and 100 μmol/L. Results showed that the growth of Chlorella sp. was not significantly inhibited when the zinc concentrations were less than 5 and 10 μmol/L for zinc citrate and zinc chloride, respectively. But the growth was significantly inhibited at the concentrations of 5 μmol/L for each of zinc acetate and zinc gluconate, and the algal biomass rapidly decreased with the increases of Zn²⁺ concentrations for the two zinc salts. The results also showed that the amounts of heat-stable proteins significantly increased in Chlorella sp. exposed to the four kinds of zinc salts compared with that of the control group (without adding any zinc salt), and the largest amount of heat-stable proteins was obtained when the algae were exposed to zinc gluconate at 50 μmol/L for 3 days, producing 34.5 mg of heat-stable proteins per gram of wet algae mud, which was 3.3 times higher than that of the control group. And the largest amount of Zn-MTs was induced under the inducing condition.