Abstract
Photodynamic antimicrobial chemotherapy (PAC) is an efficient tool for inactivating microorganisms. This technique is a good approach to inactivate the foodborne microorganisms, which are responsible for one of the major public health concerns worldwide—the foodborne diseases. In this work, response surface methodology (RSM) was used to evaluate the interaction of Eosin Y (EOS) concentration and irradiation time on Staphylococcus aureus counts and a sequence of designed experiments to model the combined effect of each factor on the response. A second-order polynomial empirical model was developed to describe the relationship between EOS concentration and irradiation time. The results showed that the derived model could predict the combined influences of these factors on S. aureus counts. The agreement between predictions and experimental observations (R2adj = 0.9159, p = 0.000034) was also observed. The significant terms in the model were the linear negative effect of photosensitizer (PS) concentration, followed by the linear negative effect of irradiation time, and the quadratic negative effect of PS concentration. The highest reductions in S. aureus counts were observed when applying a light dose of 9.98 J/cm2 (498 nM of EOS and 10 min. irradiation). The ability of the evaluated model to predict the photoinactivation of S. aureus was successfully validated. Therefore, the use of RSM combined with PAC is a promising approach to inactivate foodborne pathogens.
Highlights
Foodborne diseases are a public health problem that compromise health care systems and harm national economies; besides this, they are an important cause of morbidity and mortality worldwide [1].According to the Centers for Disease Control and Prevention [2], Staphylococcus aureus was responsibleAntibiotics 2020, 9, 125; doi:10.3390/antibiotics9030125 www.mdpi.com/journal/antibioticsAntibiotics 2020, 9, 125 for 671 outbreaks with 526 hospitalizations between 1998–2016 in the United States, becoming one of the top five pathogens that cause foodborne disease.Preventing outbreaks of foodborne disease requires the control of microorganisms in the food production chain
An efficient tool for inactivating microorganisms is photodynamic antimicrobial chemotherapy (PAC), which is a promising and low-price technology that is effective against a several types of foodborne bacteria [3,5,6,7,8]
An aliquot of 25 μL of bacterial suspension standardized at 107 colony-forming units (CFU)/mL was homogenized with 475 μL Eosin Y (EOS) at different concentrations in a 24-well microplate; the mixture was incubated for 10 min in the dark, and illuminated with a green light-emitting diode (LED) light (PS+L+) up to the maximum time of
Summary
Foodborne diseases are a public health problem that compromise health care systems and harm national economies; besides this, they are an important cause of morbidity and mortality worldwide [1]. The conventional methodologies used in food preservation are related to some undesirable characteristics such as the possibility of induced physical and chemical changes in food, high costs, and a requirement for high investment and specialized equipment [3,4] In this context, an efficient tool for inactivating microorganisms is photodynamic antimicrobial chemotherapy (PAC), which is a promising and low-price technology that is effective against a several types of foodborne bacteria [3,5,6,7,8]. This method requires a large number of experiments and would provide biased results, once there are some interactions between factors [23] In this sense, response surface methodology (RSM), a method that combines statistical and mathematical techniques to infer a multivariate model, could optimize the analyses significantly reducing the number of experiment trails [23,24,25]. The present study was undertaken to develop response surface models to evaluate the interaction of eosin Y concentration and illumination time using green light-emitting diodes in the PAC against Staphylococcus aureus ATCC 25923
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