| Summary: | Bacteria in planktonic and biofilm forms exhibit different phenotypic properties. In this study, the phenotypic traits and probiotic functions of <i>Lactiplantibacillus plantarum</i> Y42 in planktonic and biofilm forms were assessed. After 36 h of static culture, scanning electron microscopy and confocal laser scanning microscopy showed that the <i>L</i>. <i>plantarum</i> Y42 bacterial cells contained interconnected adhesive matter on the surface, forming a ~18 μm layer of dense biofilms. The surface properties of <i>L</i>. <i>plantarum</i> Y42 in biofilm form, including autoaggregation ability, hydrophobicity, acid-base charge, and adhesiveness, were all higher than those in the planktonic form. Biofilm <i>L</i>. <i>plantarum</i> Y42 showed a higher tolerance to adverse environmental conditions and a higher survival rate, enzymatic activity, and integrity after vacuum lyophilization. And biofilm <i>L</i>. <i>plantarum</i> Y42 had higher adhesion to human enterocyte HT-29 cell monolayers, inhibited the expressions of proinflammatory factors IL-6 and TNF-α, and promoted the expressions of the anti-inflammatory factor IL-10 and barrier proteins Claudin-1 and Occludin. In addition, <i>L</i>. <i>plantarum</i> Y42 in biofilm form can inhibit the adhesion and invasion of <i>Listeria monocytogenes</i> ATCC 19115 to HT-29 cell monolayers and is more effective in relieving the inflammatory reactions and injuries of HT-29 cells caused by <i>L. monocytogenes</i> ATCC 19115. In conclusion, <i>L</i>. <i>plantarum</i> Y42 in biofilm form exhibited better probiotic functions compared to that in planktonic form. This indicated that <i>L. plantarum</i> Y42 can form biofilms to enhance its probiotic functions, which provided a theoretical basis for better development and utilization of <i>L. plantarum</i> Y42.
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