Influence of heavy metal stress on morphology and physiology of Penicillium chrysogenum during bioleaching process

In order to improve the efficiency of bioleaching heavy metal from the contaminated soil using Penicillium chrysogenum (P. chrysogenum), experiment was conducted to evaluate the influence of heavy metal stress on P. chrysogenum during bioleaching. The morphology and physiology of P. chrysogenum were observed. Assuming that the heavy metals are all leached out from the experiment soil, heavy metals are added into the agar medium by simulating the heavy metal content in the soil. It is concluded that the survivable heavy metal contaminated soil mass range for P. chrysogenum is 2.5–5.0 g. As for biomass determination, the contaminated soil is added into the liquid medium directly. The soil mass that P. chrysogenum can be survivable is in the range of 2.5–8.75 g. In this mass range, the biomass of P. chrysogenum is bigger than that of the control sample. 10 g soil mass is the threshold of the growth of P. chrysogenum. 102.2 mg/L gluconic acid, 156.4 mg/L oxalic acid, 191.6 mg/L pyruvic acid, 0.02 mg/L citric acid, 0.03 mg/L malic acid and 70.6 mg/L succinic acid are determined after 15 d bioleaching. The mycelium is broken into fragments, and heavy metals are adsorbed on the cell wall or transported into the cytoplasm during bioleaching. The GOD activity declines from 1.08 U/mL to 0.2 U/mL under 400 mg/L of multi-metal stress. The influence of Pb on GOD activity is bigger than that of Cr and Cd, and the GOD activity is not influenced apparently by Mn, Zn and Cu.