Characterization of nigerlysin ©, hemolysin produced by Aspergillus niger, and effect on mouse neuronal cells in vitro

Aspergillus niger produced a proteinaceous hemolysin, nigerlysin © when incubated on sheep's blood agar (SBA) at both 23 and 37 °C. Nigerlysin was purified from tryptic soy broth (TSB) culture filtrate and found to have a molecular weight of approximately 72 kDa, with an isoelectric point of 3.45. Nigerlysin is heat stable up to 65 °C but unstable at 75 °C when incubated for 10 min. Circular dichroic analysis revealed that nigerlysin has an alpha helical structure. Exposure of mouse primary cortical neuronal cells to 0.1 μg ml−1 of nigerlysin resulted in the rapid loss of their viability, approximately 50% in 24 h. The IC50 is estimated to be 0.037 μg ml−1, or between 0.034 and 0.041 μg ml−1 at the 95% confidence level.