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Salmonella is a food-borne microorganism that is also a zoonotic bacterial hazard in the food sector. This study determined how well a mixed culture of Salmonella Kentucky formed biofilms on plastic (PLA), silicon rubber (SR), rubber gloves (RG), chicken skin and eggshell surfaces. In vitro interactions between the histone deacetylase inhibitor-vorinostat (SAHA)-and S. enterica serotype Kentucky were examined utilizing biofilms. The minimum inhibitory concentration (MIC) of SAHA was 120 µg mL -1 . The addition of sub-MIC (60 µg mL -1 ) of SAHA decreased biofilm formation for 24 h on PLA, SR, RG, Chicken skin, and eggshell by 3.98, 3.84, 4.11, 2.86 and 3.01 log ( p  < 0.05), respectively. In addition, the initial rate of bacterial biofilm formation was higher on chicken skin than on other surfaces, but the inhibitory effect was reduced. Consistent with this conclusion, virulence genes expression ( avrA, rpoS and hilA ) and quorum-sensing (QS) gene ( luxS ) was considerably downregulated at sub-MIC of SAHA. SAHA has potential as an anti-biofilm agent against S. enterica serotype Kentucky biofilm, mostly by inhibiting virulence and quorum-sensing gene expression, proving the histone deacetylase inhibitor could be used to control food-borne biofilms in the food industry.

Food contamination is a major public health concern, with Salmonella Typhimurium, Escherichia coli, and Pseudomonas aeruginosa being the prominent causal agents. They often produce resistant shields in food through biofilm formation and are difficult to remove from food-contact surfaces using conventional cleaning agents. In the current study, we investigated the efficacy of flavourzyme, an industrial peptidase, in biofilm removal from ultra-high molecular weight polyethylene (UHMWPE) and rubber surfaces and compared the corresponding efficacies with those of the commonly used DNase I. We noticed a significant reduction of young (24-h-old) and mature (72-h-old) biofilms on both surfaces after treatment with flavourzyme. The overall reduction potentiality of flavourzyme was higher than that of DNase I. The flavourzyme-mediated removal of biofilms appears to be caused by the gradual disruption of amide (NH) and polysaccharide (C-O-C) stretching bands of the extracellular polymeric substances (EPS) released by the microbes. EPS elimination and the cell-friendly behavior of flavourzyme were further confirmed by field emission scanning electron microscopy. Based on these findings, we suggest that flavourzyme can reduce microbial EPS formation, thus possibly controlling microbial food contamination. This finding reveals a new opportunity for the development of a novel method for controlling foodborne illness as well as food spoilage., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The purpose of this research was to characterize Listeria monocytogenes from several environmental and clinical sources and assess the efficacy of single and combined physico-chemical treatments in reducing biofilm on lettuce leaves. PCR analysis of L. monocytogenes isolates collected from different clinical (10 strains) and environmental sources (12 strains) was used to look for the presence of one Listeria -specific gene and five virulence genes. Biofilms of L. monocytogenes were developed on lettuce leaves over 24 h. A 5-min ultrasound and a 300-ppm sodium hypochlorite (NaOCl) wash resulted in similar reductions in cell numbers of 0.82 log CFU cm -2 . For chlorine dioxide (ClO 2 ) at 60 ppm, the cell numbers were reduced by ∼5.45 log CFU cm -2 . A combined treatment of 5 min of ultrasound plus 300 ppm NaOCl or 40 ppm ClO 2 , provided maximal efficacy, reducing the number of L. monocytogenes on the lettuce surface to non-detectable levels. Therefore, ClO 2 has the potential to replace NaOCl for the disinfection of food products in the food industry.

Salmonella is one of the main foodborne pathogens that affect humans and farm animals. The Salmonella genus comprises a group of food-transmitted pathogens that cause highly prevalent foodborne diseases throughout the world. The aim of this study was to appraise the viability of Salmonella Typhimurium biofilm under water treatment at room temperature on different surfaces, specifically stainless steel (SS), plastic (PLA), rubber (RB), and eggshell (ES). After 35 D, the reduction of biofilm on SS, PLA, RB, and ES was 3.35, 3.57, 3.22, and 2.55 log CFU/coupon without water treatment and 4.31, 4.49, 3.50, and 1.49 log CFU/coupon with water treatment, respectively. The d R value (time required to reduce bacterial biofilm by 99% via Weibull modeling) of S. Typhimurium without and with water treatment was the lowest on PLA (176.86 and 112.17 h, respectively) and the highest on ES (485.37 and 2,436.52 h, respectively). The viability of the S. Typhimurium on ES and the 3 food-contact surfaces was monitored for 5 wk (35 D). The results of this study provide valuable information for the control of S. Typhimurium on different surfaces in the food industry, which could reduce the risk to consumers., (Copyright © 2020. Published by Elsevier Inc.)

Biofilm reactors retain microbial cells in the form of biofilm which is attached to free moving or fixed carrying materials, thus providing a high active biomass concentration and automatic liquid and solid separation. Nowadays, microbial biofilm reactors have been widely used in high-strength wastewater treatment where very high pollutant removal efficiency is required, which usually requires excessive space and aeration energy for conventional activated sludge-based treatment. This paper provides an overview of microbial biofilm reactors developed over the last half-century, including moving bed biofilm reactor (MBBR), trickling filter (TF) reactor, rotating biological contactor (RBC), membrane biofilm reactor (MBfR), passive aeration simultaneous nitrification and denitrification (PASND) biofilm reactor, for their applications in high-strength wastewater treatment of not only removing carbon, nitrogen, sulphur but also a variety of oxidized contaminants including perchlorate and bromate. Despite the advance of biofilm reactor that exhibits high resistance to excessive pollutants loading, its drawbacks both from engineering and microbiological point of view are reviewed. The future prospects of biofilm reactor are also discussed in this review paper.

Conventional aerobic treatment of high-strength wastewater is not economical due to excessively high energy requirement for compressed air supply. The use of passive aeration avoids the use of compressed air and enables energy efficient oxygen supply directly from the air. This study evaluates a passively aerated simultaneous nitrification and denitrification performing biofilm to treat concentrated wastewater. The biofilm reactor was operated > 5-months under alternating anaerobic/aerobic conditions. For 4-times concentrated wastewater, > 80% COD (2307 mg L -1  h -1 ) and > 60% N (60 mg L -1  h -1 ) was removed at a hydraulic retention time (HRT) of 7 h. A double application in the same reactor enabled > 95% COD and 85% N-removal, at an overall HRT of 14 h which is substantially shorter than what traditional activated sludge-based systems would require for the treatment of such concentrated feeds. Microbial community analysis showed Candidatus competibacter (27%) and nitrifying bacteria (Nitrosomonas, and Nitrospira) as key microbes involved in COD and N-removal, respectively., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The current paper describes a novel passive aeration simultaneous nitrification and denitrification (PASND) zeolite amended biofilm reactor that removes organic carbon and nitrogen from wastewater with low-energy consumption. Next to the ammonium oxidizing bacteria (AOB), this reactor contained naturally enriched glycogen accumulating organisms (GAOs) and zeolite powder to initially adsorb BOD (acetate) and ammonium (NH 4 + -N) from synthetic wastewater under anaerobic conditions. Draining of the treated wastewater exposed the biofilm directly to air enabling low-energy oxygen supply by passive aeration. This allowed the adsorbed ammonium to be oxidized by the AOB and the produced nitrite and nitrate to be reduced simultaneously by the GAOs using the adsorbed BOD (stored as PHAs) as carbon source. Overall, with an operation mode of 1 h anaerobic and 4 h aerobic phase, the nutrient removal efficiency after single treatment was about 94.3% for BOD and 72.2% for nitrogen (NH 4 + -N). As high-energy aeration of the bulk solution for oxygen supply is completely avoided, the energy requirement of the proposed PASND biofilm reactor can be theoretically cut down to more than 50% compared to the traditional activated sludge process.

The cost associated with treatment and disposal of excess sludge produced is one of the greatest operational expenses in wastewater treatment plants. In this study, we quantify and explain greatly reduced excess sludge production in the novel glycogen accumulating organism (GAO) dominated drained biofilm system previously shown to be capable of extremely energy efficient removal of organic carbon (biological oxygen demand or BOD) from wastewater. The average excess sludge production rate was 0.05 g VSS g -1 BOD (acetate) removed, which is about 9-times lower than that of comparative studies using the same acetate based synthetic wastewater. The substantially lower sludge yield was attributed to a number of features such as the high oxygen consumption facilitated by direct oxygen uptake from air, high biomass content (21.41 g VSS L -1 of reactor), the predominance of the GAO (Candidatus competibacter) with a low growth yield and the overwhelming presence of the predatory protozoa (Tetramitus) in the biofilm. Overall, the combination of low-energy requirement for air supply (no compressed air supply) and the low excess sludge production rate, could make this novel "GAO drained biofilm" process one of the most economical ways of biological organic carbon removal from wastewater., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The current paper describes a novel passive aeration simultaneous nitrification and denitrification (PASND) zeolite amended biofilm reactor that removes organic carbon and nitrogen from wastewater with low-energy consumption. Next to the ammonium oxidizing bacteria (AOB), this reactor contained naturally enriched glycogen accumulating organisms (GAOs) and zeolite powder to initially adsorb BOD (acetate) and ammonium (NH4+-N) from synthetic wastewater under anaerobic conditions. Draining of the treated wastewater exposed the biofilm directly to air enabling lowenergy oxygen supply by passive aeration. This allowed the adsorbed ammonium to be oxidized by the AOB and the produced nitrite and nitrate to be reduced simultaneously by the GAOs using the adsorbed BOD (stored as PHAs) as carbon source. Overall, with an operation mode of 1 h anaerobic and 4 h aerobic phase, the nutrient removal efficiency after single treatment was about 94.3% for BOD and 72.2% for nitrogen (NH4+-N). As high-energy aeration of the bulk solution for oxygen supply is completely avoided, the energy requirement of the proposed PASND biofilm reactor can be theoretically cut down to more than 50% compared to the traditional activated sludge process. [ABSTRACT FROM AUTHOR]

Glycogen accumulating organisms (GAO) are known to allow anaerobic uptake of biological oxygen demand (BOD) in activated sludge wastewater treatment systems. In this study, we report a rapid transition of suspended activated sludge biomass to a GAO dominated biofilm by selective enrichment using sequences of anaerobic loading followed by aerobic exposure of the biofilm to air. The study showed that within eight weeks, a fully operational, GAO dominated biofilm had developed, enabling complete anaerobic BOD uptake at a rate of 256 mg/L/h. The oxygen uptake by the biofilm directly from the atmosphere had been calculated to provide significant energy savings. This study suggests that wastewater treatment plant operators can convert activated sludge systems readily into a “passive aeration” biofilm that avoids costly oxygen transfer to bulk wastewater solution. The described energy efficient BOD removal system provides an opportunity to be coupled with novel nitrogen removal processes such as anammox. [ABSTRACT FROM AUTHOR]

[Display omitted] • Postbiotics from Lactobacillus spp. bacteria were characterized. • Antibacterial and antibiofilm activity of postbiotics against Listeria monocytogenes were measured. • Postbiotics suppresses the expression of L. monocytogenes virulence genes. • Postbiotics can be considered as preventive tools against L. monocytogenes. Owing to their preservative and antimicrobial effects, postbiotics (metabolic byproducts of probiotics) are promising natural components for the food industry. Therefore, the present study aimed to investigate the efficacy of postbiotics collected from isolated Lactobacillus curvatus B.67 and Lactobacillus plantarum M.2 against Listeria monocytogenes pathogens in planktonic cells, motility, and biofilm states. The analysis of the metabolite composition of the postbiotics revealed various organic acids, along with a few well-known bacteriocin-encoding genes with potential antimicrobial effects. Postbiotics maintained their residual antimicrobial activity over the pH range 1–6 but lost all activity at neutral pH (pH 7). Full antimicrobial activity (100%) was observed during heat treatment, even under the autoclaving condition. Minimum inhibitory concentration (MICs) of L. curvatus B.67 and L. plantarum M.2 against L. monocytogenes were 80 and 70 mg/mL, respectively. However, four sub-MICs of the postbiotics (1/2, 1/4, 1/8, and 1/16 MIC) were tested for inhibition efficacy against L. monocytogenes during different experiment in this study. Swimming motility, biofilm formation, and expression levels of target genes related to biofilm formation, virulence, and quorum-sensing were significantly inhibited with increasing postbiotics concentration. Postbiotics from L. plantarum M.2 exhibited a higher inhibitory effect than the postbiotics from L. curvatus B.67. Nonetheless, both these postbiotics from Lactobacillus spp. could be used as effective bio-interventions for controlling L. monocytogenes biofilm in the food industry. [ABSTRACT FROM AUTHOR]

Salmonellosis is a prevalent food poisoning disease caused by Salmonella spp. that affects millions of people throughout the world. Contamination of chicken meat and processing equipment with Salmonella is a major issue in the food industry. Therefore, it is necessary to study not only food but also food contact surfaces [plastic (PLA) and rubber gloves (RG)] that can cause cross-contamination during processing. The inhibitory activities of quercetin, an antioxidant and antibacterial compound, were tested against S. Typhimurium and S. Enteritidis on PLA, RG, and chicken skin during biofilm. When quercetin (0–125 μg/mL) was supplemented, the inhibitory effect was 1.50–2.61 log CFU/cm2 (125; 1/2, 62.5; 1/4, and 31.25 μg/mL; 1/8 MIC). Furthermore, the initial biofilm formation rate of both bacteria was greater on the chicken skin surface than on the food contact surfaces. The inhibitory impact was visually observed using field-emission scanning electron microscopy and confocal laser scanning microscopy. The swimming and swarming motility was also found to be inhibited from 1/8 MIC. As determined by qRT-PCR, quercetin downregulated the expression levels of virulence (avrA , and hilA), stress response (rpoS), and quorum-sensing (luxS) genes. Our findings suggest that plant-derived quercetin is a possible antibiofilm agent against Salmonella spp. biofilm formation, as well as biofilm caused by other bacteria. •Quercetin inhibits foodborne pathogen biofilm formation •It downregulates the virulence, stress response, and quorum sensing gene expression •It can be used as an antioxidant derived from natural plant [ABSTRACT FROM AUTHOR]

Salmonella is a foodborne pathogen and an emerging zoonotic bacterial threat in the food industry. The aim of this study was to evaluate the biofilm formation by a cocktail culture of 3 wild isolates of Salmonella enterica serotype Kentucky on plastic (PLA), silicon rubber (SR), and chicken skin surfaces under various temperatures (4, 10, 25, 37, and 42°C) and pH values (4.0, 5.0, 6.0, 7.0, and 8.0). Then, at the optimum temperature and pH, the effects of supplementation with glucose (0, 0.025, 0.05, and 0.4% w/v) on biofilm formation were assessed on each of the surfaces. The results indicated that higher temperatures (25 to 42°C) and pH values (7.0 and 8.0) led to more robust biofilm formation than lower temperatures (4 and 10°C) and lower pH levels (4.0 to 6.0). Moreover, biofilm formation was induced by 0.025% glucose during incubation at the optimum temperature (37°C) and pH (7.0) but inhibited by 0.4% glucose. Consistent with this finding, virulence related gene (rpoS, rpoH, hilA , and avrA) expression was increased at 0.025% glucose and significantly reduced at 0.4% glucose. This results also confirmed by field emission scanning electron microscope, confocal laser scanning microscopy, and autoinducer-2 determination. This study concluded that optimum environmental conditions (temperature 37°C, pH 7.0, and 0.25% glucose) exhibited strong biofilm formation on food and food contract surfaces as well as increased the virulence gene expression levels, indicating that these environmental conditions might be threating conditions for food safety. [ABSTRACT FROM AUTHOR]