Recent studies in lactic acid bacteria (LAB) biofilm formation have reported that the functional properties of LAB are associated with biofilm formation. In this study, Pediococcus acidilactici and Lactobacillus plantarum showed the ability to form a biofilm on a solid surface under static conditions. The morphology of LAB on MRS-CR agar showed that both P. acidilactici and L. plantarum could produce exopolysaccharide (EPS) on the cell surface which mainly contributed to forming the biofilm of single and co-culture strains on solid surfaces. Under the flow condition, cell motility played an important role in supporting the cell to overcome the repulsive force to reach and interact with the surface. As a result, the L. plantarum and co-culture cells with higher motility caused a noticeably thicker biofilm on the glass surface compared to the P. acidilactici strain. Moreover, the antagonistic activity assay showed that co-culture biofilm formation improved the antagonistic effects of LAB against Pseudomonas aeruginosa and Salmonella typhimurium compared to those in planktonic culture. It suggested that co-culture biofilm could be an ef fective model to apply useful LAB as potential probiotics and to control pathogen in food chain, especially under the flow condition.

A novel bacterial strain, N4T, was isolated from the soil of a groundnut Arachis hypogaea field in Nghean province, Vietnam. The phylogenetic, chemotaxonomic and phenotypic characteristics of this strain were determined. Cells of strain N4T were Gram-negative, aerobic, endospore-forming and rod-shaped. Strain N4T grew at 20–37 °C (optimum, 30 °C), pH 6–10 (optimum, pH 7) and 0–5 % NaCl (optimum, 0 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain N4T belonged to the genus Paenibacillus and was closely related to Paenibacillus harenae B519T (=KCTC 3951T) and Paenibacillus alkaliterrae KSL-134T (=KCTC 3956T) with 96.3 and 96.5% gene sequence similarity, respectively. It contained meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 52.9 mol%. The major isoprenoid quinone was MK-7. Anteiso-C15 : 0 and iso-C16 : 0 were the dominant cellular fatty acids. Based on phylogenetic, physiological and biochemical characteristics, strain N4T represents a novel species of the genus Paenibacillus , for which the name Paenibacillus vietnamensis sp. nov. is proposed. The type strain is N4T (=KCTC 33932T= VTCC 12236T).