Journal Articles
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Item Enzymatic dispersion of pseudomonad biofilms grown at psychrotrophic temperature(Elsevier Ltd on behalf of Institution of Chemical Engineers, 2026-01-01) Muthuraman S; Palmer J; Flint SPseudomonads are robust biofilm formers in psychrotrophic temperatures, which can cause spoilage in dairy, poultry, and meat processing. This study screened eleven isolates for the biofilm-forming ability using the Congo Red Assay (CRA) and the crystal violet assay. Two isolates, 3SM and 20SM, showed significantly higher EPS production, cellulose synthesis and cell count at 4ºC and were selected for the enzymatic dispersion. Mature biofilms formed on the stainless-steel surface for 72 h at 4°C were treated with laboratory enzymes (Proteinase-K, Cellulase, and DNase I) and commercial enzymes (formulated cleaners, EnduroZyme, DualZyme, and TriZyme). Compared to laboratory enzymes, commercial enzymes were efficient in dispersing the biofilms (EnduroZyme- 62 %, DualZyme- 42 %, and TriZyme-32 % of biofilm removal), which was confirmed by cell counts, crystal violet assay, and microscopic observations. However, none of the treatments resulted in complete biofilm dispersion. These findings highlight the resilience of psychrotrophic pseudomonad biofilms and underscore the need for improved enzymatic strategies tailored for cold-chain environments.Item Sequential treatment of psychrotrophic pseudomonad biofilms with sodium hydroxide and commercial enzyme cleaners(Elsevier Ltd, United Kingdom, 2026-04) Muthuraman S; Palmer J; Flint SPseudomonads are psychrotrophic spoilage bacteria that can form biofilms at the air-liquid interface. Food processing utensils and equipment often facilitate the air-liquid interface biofilm formation. Pseudomonads produce thermostable enzymes and pigments that affect the organoleptic quality of perishable food products. In this study, Pseudomonas lundensis, Pseudomonas cedrina were allowed to form biofilms at 4 °C under continuous flow of nutrients in a CDC reactor (CBR 90; Biosurface Technologies, USA). The mature biofilms were treated with commercial enzyme cleaners, EnduroZyme (protease), DualZyme (protease and lipase), and TriZyme (protease, amylase, and cellulase). The dispersion with EnduroZyme was significantly (p < 0.05) higher than the other enzyme cleaners. Then the biofilms were treated with hot water and sodium hydroxide, and enzyme cleaners (sequential treatment). The cell counts after sodium hydroxide + Enzyme cleaners were below the detection limit. The microscopic observations with epifluorescence microscopy showed that the coupons had less fluorescence after the sequential treatment. FTIR observations showed that the extracellular polymeric substances (EPS) isolated after sodium hydroxide + enzyme cleaners differed from the untreated and sodium hydroxide-only-treated EPS. Biofilm regrowth was significantly (p < 0.05) lower in the biofilms treated with sodium hydroxide + EnduroZyme compared to acid-treated control coupons. The sequential treatment with sodium hydroxide and enzyme cleaners reduced the biofilm footprints, representing a better clean than enzyme treatment alone or sodium hydroxide-only cleaning.