Effect of Sonication on Microwave Inactivation Kinetics of IEnterococcus faecalis/I in Dairy Effluent

• Published in: Molecules (Basel, Switzerland) Switzerland), 2022-11, Vol.27 (21)
• Main Authors: Kernou, Ourdia-Nouara, Belbahi, Amine, Sahraoui, Yasmine, Bedjaoui, Kenza, Kerdouche, Kamelia, Amir, Akila, Dahmoune, Farid, Madani, Khodir, Rijo, Patricia
• Format: Article
• Language: English
• Subjects: Analysis; Dairy industry; Wastewater
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules27217422

The aim of this study is to inactivate Enterococcus faecalis ATCC 29212 present in dairy wastewater effluent using microwave (MW) waves and/or ultrasound waves (US). The ultrasonic bath treatment (35 kHz) had no significant effect on the reduction of the survival rate (predominant declumping effect). At 650 W of microwave treatment, the total destruction was completed at 75 s, while at 350 W a 3 log reduction was achieved. The Weibull model was fitted to the survival curves to describe the inactivation kinetics, and the effect of the combined microwave-ultrasound treatments was evaluated. The scaling parameter α that was estimated from the inactivation kinetics for the microwaves combined with the ultrasound waves in pre-treatment was found to be lower than the scaling parameters obtained in post-treatment, which were in turn lower than those estimated for microwaves or ultrasound waves alone. The use of the ultrasound waves in pre-treatment was more effective than in post-treatment; a total reduction was achieved using a combination of US (30 min) followed by MW (650 W) with α = 28.3 s, while 4.0 log was obtained by reversing all processes with α = 34.5 s. The results from the protein assays indicate that the bacterial wall was damaged and that holes were formed from which protein leakage occurred.