No abstract

Escherichia coli (E. coli) is associated with an array of health-threatening contaminations, some of which are related to biofilm states. The pgaABCD-encoded poly-beta-1,6-N-acetyl-D-glucosamine (PGA) polymer plays an important role in biofilm formation. This study was conducted to determine the inhibitory effect of gallic acid (GA) against E. coli biofilm formation. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of GA against planktonic E. coli were 0.5 and 4 mg/mL, and minimal biofilm inhibitory concentration and minimal biofilm eradication concentration values of GA against E. coli in biofilms were 2 and 8 mg/mL, respectively. Quantitative crystal violet staining of biofilms and ESEM images clearly indicate that GA effectively, dose-dependently inhibited biofilm formation. CFU counting and confocal laser scanning microscopy measurements showed that GA significantly reduced viable bacteria in the biofilm. The contents of polysaccharide slime, protein, and DNA in the E. coli biofilm also decreased. qRT-PCR data showed that at the sub-MIC level of GA (0.25 mg/mL) and expression of pgaABC genes was downregulated, while pgaD gene expression was upregulated. The sub-MBC level of GA (2 mg/mL) significantly suppressed the pgaABCD genes. Our results altogether demonstrate that GA inhibited viable bacteria and E. coli biofilm formation, marking a novel approach to the prevention and treatment of biofilm-related infections in the food industry.

This article studied the volatile composition and content in 12 oat groats and flakes. Half of them were naked ones, and the other half were covered ones. Volatile compounds were compared between (i) naked and covered oat groats, (ii) naked and covered oat flakes, and (iii) oat groats and flakes to find out the changes in both composition and content with application of HS/SPME‐GC/MS and multivariate analysis including principal component analysis and cluster analysis. Most oat flakes have higher sensory ranks compared to their oat groats, corresponding with the fact that processing improves the sensory properties of oat groats. The cluster analysis based on volatile contents showed no significant difference between covered oat samples and naked oat samples. Practical applications Oat flakes vary in flavor due to variety and distinct processing in each factory. However, few researches on volatile compounds in oats have been conducted. This article investigated the volatile compounds in Chinese naked and covered oat groats and flakes to find out if there were correlations between volatile composition and the oat varieties, geographic provenance, or processing of the samples. The research adds to the study of volatile compounds in Chinese oats.