Abstract
A submerged dielectric barrier discharge plasma reactor (underwater DBD) has been used to inactivate biofilm produced by three different food-borne pathogens, namely Escherichia coli O157:H7 (ATCC 438), Cronobacter sakazakii (ATCC 29004), and Staphylococcus aureus (KCCM 40050). The inactivation that were obtained after 90 minutes of plasma operation were found to measure 5.50 log CFU/coupon, 6.88 log CFU/coupon and 4.20 log CFU/coupon for Escherichia coli O157:H7 (ATCC 438), Cronobacter sakazakii (ATCC 29004), and Staphylococcus aureus (KCCM 40050), respectively. Secondary Electron Images (SEI) obtained from Field Emission Scanning Electron Microscopy (FE-SEM) show the biofilm morphology and its removal trend by plasma operation at different time intervals. An attenuated total reflectance Fourier transform infrared (ATR-FTIR) measurement was performed to elucidate the biochemical changes that occur on the bacterial cell and extracellular polymeric substance (EPS) of biofilm during the plasma inactivation process. The ATR-FTIR measurement shows the gradual reduction of carbohydrates, proteins, and lipid and DNA peak regions with increased plasma exposure time. The presence of an EPS layer on the upper surface of the biofilm plays a negative and significant role in its removal from stainless steel (SS) coupons.
Highlights
Microorganisms are able to aggregate on wet surfaces and grow into microcolonies to form biofilms
Biofilms were generated on stainless steel coupons under laboratory conditions for three reference strains of the most frequently encountered food-borne pathogens, such as Escherichia coli O157:H7 (ATCC 438), Cronobacter sakazakii (ATCC 29004), and Staphylococcus aureus (KCCM 40050), to observe the degradation effect and inactivation mechanism of plasma on food-borne pathogens
Underwater Dielectric barrier discharges (DBD) plasma was employed on a stainless steel (SS) coupon containing a biofilm from the three reference strains Escherichia coli O157:H7 (ATCC 438), Cronobacter sakazakii (ATCC 29004), and Staphylococcus aureus (KCCM 40050)
Summary
Microorganisms are able to aggregate on wet surfaces and grow into microcolonies to form biofilms. The non-thermal plasma method works at room temperature, and because of its high efficiency and safety, it has been shown to be appropriate for various applications such as the surface modification of polymers[13,14,15], air purification[16,17], and sterilization for biological and medical purposes[18,19,20,21]. Underwater electrical discharge is a fast and reliable non-thermal plasma technique that has been used extensively for microbial inactivation[22,23,24,25,26,27,28,29]. The complete elimination of microorganisms depends on several factors such as the plasma power, the gas, the type of bacteria, and the type of medium
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