The emergence of the antimicrobial resistance phenomena on and the harmful consequences of the use of antibiotics motivate the necessity of innovative antimicrobial therapies, while natural substances are considered a promising alternative. Rosmarin is an original plant compound listed among the hydroxycinnamic acids. This substance has been widely used to fight microbial pathology and chronic infections from microorganisms like bacteria, fungi and viruses. Also, various derivatives of rosmarinic acid, such as the propyl ester of rosmarinic acid, rosmarinic acid methyl ester or the hexyl ester of rosmarinic acid, have been synthesized chemically, which have been isolated as natural antimicrobial agents. Rosmarinic acid and its derivatives were combined with antibiotics to obtain a synergistic effect. This review reports on the antimicrobial effects of rosmarinic acid and its associated derivatives, both in their free form and in combination with other microbial pathogens, and mechanisms of action.

The survival of Escherichia coli ATCC 25922 in orange juice treated with microwave and/or ultrasound was evaluated; Weibull model was fitted to survival curves to describe inactivation kinetics; and the effect of combined microwave‐ultrasound treatments was assessed. Ultrasonic treatment (42 kHz) has no significant effect on the survival rate reduction (1.3 log for 60 min of sonication) of E. coli. However, sonication can increase the efficiency of microwave inactivation. The use of ultrasound as pre‐treatment was more effective than when used in post‐treatment, that is, a reduction of 8.0 log was achieved by a combination of ultrasound (20 min) followed by a microwave (900 W/30 s), while 4.0 log was obtained when these both processes were reversed. The scale parameter α estimated from microwave‐inactivation kinetics combined with an ultrasound pre‐treatment was found to be lower than those obtained with a post‐treatment, which, in turn, are lower than those estimated for microwave or ultrasound alone. These results demonstrate the effectiveness of ultrasound as a pre‐treatment to improve the inactivation of E. coli by microwave processing in orange juice beverages. Practical applications High‐temperature short‐time (HTST) type processes are preferred by the food industry to reduce the adverse thermal degradation in food quality while ensuring food safety for liquid food. The microwave heating is fast and can significantly reduce the come‐up time to the desired process temperature. The hydrodynamic action of ultrasound on microorganisms is a great potential to improve microbial decontamination efficiency by microwave processing. This study contributes to the design and control of an effective combination treatment of ultrasound and microwave to improve pasteurization processes for orange juice beverages.

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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.

Background and aims: The Weibull model was fitted to survival curves in order to describe inactivation kinetics, and the effect of combined microwave (MW) and ultrasound (US) treatments was evaluated. Methods: Enterococcus faecalis ATCC 29212 present in 40 mL of sterile physiological water was treated with microwaves at 300W, 600W, and 900W and/or ultrasonic probes (amplitude 60 %, 80 % and 100 %, pulse (3s continuous, 3s discontinuous). Results: The use of an ultrasonic probe at 20 kHz displayed no significant impact on the patients' ability to survive. At 600 W and 300 W of MW treatment, a decrease of 3.96 log and 0.90 log, respectively, was obtained. Total destruction was accomplished in 70 seconds when 900 W of microwave therapy was used. Additionally, it was shown that the effectiveness of WM and US increased with increasing power and exposure duration. This was the case even when microwave or ultrasonic technology was utilized independently. In addition, the treatment that included both microwaves and ultrasound showed a significantly better effect than the treatment that only involved microwaves, but there were no significant differences between the coupled treatment and the microwave treatment given for 30 seconds. Conclusions: The results of the current study show that the inactivation of Enterococcus faecalis by ultrasound followed by microwave treatment was significantly higher than that obtained by microwave treatment followed by ultrasound. Keywords: Enterococcus faecalis, ultrasound, microwave, inactivation.