Initial Study On The Cell Growth And Select Metabolites Of Physarum Polycephalum In The Presence Of Excess Ferrous And Ferric Chloride Salt

Abstract

This research investigated the feasibility of Iron oxide nanoparticles (IONPs) synthesis using Physarum polycephalum, a fast growth, high biomass production without cell walls slime mold species, in the presence of excess ferric and ferrous salts. The effects of the high salt concentrations on the biomass and bioactivities of the exopolysaccharides (EPSs) of this species were also analyzed. In addition, this species has reportedly produced a high amount of EPSs, which process some significant biological activities and iron ions could suggestively influence both the growth and EPSs production. IONPs were successfully detected from the microplasmodia (biomass) of P. polycephalum in the cultures containing excess iron salts including 40 mM FeCl3·FeCl2 and 40 mM FeCl2, with the average particle size was 16 ± 6 nm and 24 ± 2 nm, respectively. There were no IONPs observed in the standard culture (3 mM FeCl2). The biomass yield of the standard culture, 40 mM FeCl3·FeCl2 culture, and 40 mM FeCl2 was 6.08 ± 0.15 g/L, 4.99 ± 0.26 g/L, and 5.34 ± 0.17 g/L, respectively. The crude EPS production of these cultures was 3.55 ± 0.09 g/L, 1.82 ± 0.09 g/L, and 2.54 ± 0.10 g/L, respectively. All the EPSs showed no antibacterial inhibition against Staphylococcus aureus at the tested concentration (20 mg/mL). However, the presence of excess concentrations of ferric salts seemed to negatively influence the antioxidant activities of the EPSs. Specifically, the antioxidant properties of the EPSs in the 40 mM FeCl3·FeCl2 and FeCl2 medium had no antioxidant activities, whereas the antioxidant activity of those in the standard medium displayed remarkable antioxidant activity at the half inhibitory concentration (IC50) of 2.93 mg/mL, which was compared with that of the ascorbic acid (0.63 mg/mL).