Probiotics can improve the microecological balance of the body and have special effects in promoting nutrient absorption, controlling intestinal infections, and regulating immune function. However, there are problems such as difficult colonization in the gastrointestinal environment and low oral bioavailability. Bacterial biofilms are organized bacterial cells that adhere to an abiotic or biotic surface and are enclosed in extracellular polymeric substances of exopolysaccharides (EPS), extracellular DNA (eDNA), proteins and lipids, with a three-dimensional spatial structure. Probiotics with the help of bacterial biofilms have obvious advantages over planktonic bacteria in stress resistance, combating pathogens and modulating the host's immune function, which provides a new research idea for the development of probiotics. This paper expounded on the advantages of probiotics with the help of bacterial biofilms, and focused on introducing substances that could promote the formation of probiotic biofilms and the mechanisms, and the safety of probiotic biofilms. Currently, research on probiotic biofilms is still in its infancy, and this paper is expected to provide references for future research in this field.
Bacteria ; Biofilms ; Extracellular Polymeric Substance Matrix ; Probiotics

Biodegradation of pyridine pollutant by microorganisms is one of the economical and effective methods to solve the environmental pollution of pyridine under high salinity conditions. To this end, screening of microorganisms with pyridine degradation capability and high salinity tolerance is an important prerequisite. In this paper, a salt-resistant pyridine degradation bacterium was isolated from the activated sludge of Shanxi coking wastewater treatment plant, and identified as a bacterium belonging to Rhodococcus on the basis of colony morphology and 16S rDNA gene phylogenetic analysis. Salt tolerance experiment showed that strain LV4 could grow and degrade pyridine with the initial concentration of 500 mg/L completely in 0%-6% saline environment. However, when the salinity was higher than 4%, strain LV4 grew slowly and the degradation time of pyridine by strain LV4 was significantly prolonged. Scanning electron microscopy showed that the cell division of strain LV4 became slower, and more granular extracellular polymeric substance (EPS) was induced to secrete in high salinity environment. When the salinity was not higher than 4%, strain LV4 responded to the high salinity environment mainly through increasing the protein content in EPS. The optimum conditions for pyridine degradation by strain LV4 at 4% salinity were 30 ℃, pH 7.0 and 120 r/min (DO 10.30 mg/L). Under these optimal conditions, strain LV4 could completely degrade pyridine with an initial concentration of 500 mg/L at a maximum rate of (29.10±0.18) mg/(L·h) after 12 h adaptation period, and the total organic carbon (TOC) removal efficiency reached 88.36%, indicating that stain LV4 has a good mineralization effect on pyridine. By analyzing the intermediate products in pyridine degradation process, it was speculated that strain LV4 achieved pyridine ring opening and degradation mainly through two metabolic pathways: pyridine-ring hydroxylation and pyridine-ring hydrogenation. The rapid degradation of pyridine by strain LV4 in high salinity environment indicates its application potential in the pollution control of high salinity pyridine environment.
Rhodococcus/genetics* ; Phylogeny ; Extracellular Polymeric Substance Matrix/metabolism* ; Sewage ; Biodegradation, Environmental ; Pyridines/metabolism*