Inactivation and removal of Klebsiella michiganensis biofilm attached to the inner surfaces of piping by plasma-activated microbubble water (PMBW)

Plasma-activated microbubble water (PMBW) is an environmentally friendly sanitizer that possesses potent antimicrobial activities and imparts substantial shear stress to food contact surfaces. In this study, PMBW, plasma-activated water (PAW), microbubble water (MBW), and chlorine water (100 mg/L) were used to clean PVC tubing inoculated by Klebsiella michiganensis. The sanitizer flow with microbubble was numerically simulated by COMSOL Multiphysics® and the shear stress imparted to the bacteria was calculated. The presence of microbubbles in the flow increased the shear stress imparted to the bacteria. The number of K. michiganensis on the inner surfaces of the pipes was ∼7.4 log CFU/cm2 before washing. PMBW showed the most potent antimicrobial effect, which reduced the number of bacteria by 3.1 log CFU/cm2 at a flow velocity of 1 m/s. PAW, MBW, and chlorine water reduced a similar number of bacteria (2.4 log CFU/ cm2 to 2.6 log CFU/ cm2) at all the selected flow velocities. DI water only reduced the number of K. michiganensis by 0.7 log CFU/ cm2 at 1 m/s flow velocity. PMBW can potentially be an environmentally friendly sanitizer, which can be employed by food processors to clean their food processing equipment with minimized usage of chemical sanitizers. The technology developed in this study will benefit the food industry by mitigating potential risks of foodborne pathogens without generating environmental hazards. •Flushing by plasma-activated microbubble water (PMBW) reduced the number of microbes onPVC pipes by ∼4 log CFU/cm2.•PMBW imparted greater stress to K. michiganensis than plasma-activated water did, reducing microbes by 4.1 log CFU/cm2.•The shear stresses of PMBW was ∼ 3 times of non-bubble flow and reduced ∼ 1.5 log CFU/cm2 more K. michiganensis.