Inactivation, lysis and degradation by-products of Saccharomyces cerevisiae by electrooxidation using DSA

The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO₂TiO₂ and Ti/RuO₂TiO₂IrO₂ were evaluated in 0.05 mol L^-1 Na₂SO₄ containing yeast. The results showed inactivation about of 100 % of the microorganisms at Ti/RuO₂TiO₂ by applying 20 and 60 mA cm^-2 after 120 min of electrolysis, while a complete inactivation at Ti/RuO₂IrO₂TiO₂ electrode was achieved after 180 min at 60 mA cm^-2. When chloride ions were added in the electrolyte solution, 100 % of the yeast was inactivated at 20 mA cm^-2 after 120 min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80 kWh m^-3, at 20 mA cm^-2 by using Ti/RuO₂TiO₂ anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99 kWh m^-3 at 20 mA cm^-2, for Ti/RuO₂TiO₂ and Ti/RuO₂IrO₂TiO₂ electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80 kWh m^-3 (Ti/RuO₂TiO₂) and 91.85 kWh m^-3 (Ti/RuO₂IrO₂TiO₂) to remove, respectively, 92 and 95 % of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.