A final concentration of 1 mM of transitio metal ions, such as Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+, slightly reduced its activity (95–98% of its original activity), whereas a
10 mM concentration dramatically reduced its activity (29–84% of its original activity). This coincides with the results of Rahman et al. [37], who reported that a 10 mM concentration of transition metal ions, such as Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+, could increase the interaction of ions with charged side chain groups of surface amino acids, which might markedly affect the ionization of some amino acid residues, thus rendering lipases less stable as a result of ion toxicity.