In this study, 22 strains of exopolysaccharides-producing lactic acid bacteria were isolated from silage, and the strain SSC–12 with the highest exopolysaccharide (EPS) production was used as the test strain. The SSC–12 was identified as Pediococcus pentosaceus, based upon 16S rDNA gene sequencing and Neighbor Joining (NJ) phylogenetic analysis. The analysis of the kinetic results of EPS generation of SSC–12 showed that the EPS generation reached the maximum value at 20 h of culture. The characterization study showed the EPS produced by SSC–12 was a homogeneous heteropolysaccharide comprising glucose (42.6%), mannose (28.9%), galactose (16.2%), arabinose (9.4%), and rhamnose (2.9%). The EPS had good antioxidant activity, especially the activity of scavenging hydroxyl free radicals. At the same time, the EPS also had strong antibacterial ability and could completely inhibit the growth of Staphylococcus aureus. The EPS produced by the Pediococcus pentosaceus SSC–12 can be used as a biologically active product with potential application prospects in the feed, food, and pharmaceutical industries.
Background: The exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) are widely used in various fields because of their safety and various biological activities. In this study, we extracted and characterized the composition as well as antioxidant and antibacterial activities of EPS from Pediococcus pentosaceus SSC-12 isolated from the silage.Results: The LAB strain SSC-12 was screened and identified as Pediococcus pentosaceus, based upon 16S rDNA gene sequencing and Neighbor Joining (NJ) phylogenetic analysis. The analysis of the EPS production kinetics results of SSC-12 showed that the EPS production reached the maximum at 20 h of culture. High-performance anion exchange chromatography (HPAEC) analysis showed that the EPS produced by SSC-12 was a heteropolysaccharide comprising glucose (42.6 %), mannose (28.9 %), galactose (16.2 %), arabinose (9.4 %) and rhamnose (2.9 %). The EPS had good antioxidant activity, especially hydroxyl radical scavenging activity. When the concentration of the EPS produced by SSC-12 (SSC-12 EPS) was 10 mg/mL, its 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, hydroxyl radical scavenging ability, superoxide scavenging ability, and reduction ability were 77.4 %, 97.5 %, 77.5 % and 1.3, respectively. At 10 mg/mL,SSC-12 EPS completely killed Staphylococcus aureus GDMCC 1.1220 and substantially inhibited the growth of Salmonella enterica subsp. enterica GDMCC 1.345; however, it had a weak inhibitory effect on Listeria monocytogenes GDMCC 1.347. Conclusions: Due to its strong antioxidant and antibacterial properties, EPS produced by LAB strain SSC-12 have potential application as a bioactive product in the feed, food, and pharmaceutical industries.
Background Filling silos generally takes much time in practice, which may negatively affect silage fermentation and feed intake. To clarify the effects of inoculating time, lactic acid bacteria (LAB) strains and filling time on the silage fermentation and microbes of stylo (Stylosanthes guianensis) and its silage, ensiling was quickly performed (quickly filling, QF) with or without LAB (Lactobacillus plantarum SXC48, Lb. plantarum CCZZ1 and Enterococcus faecalis XC124), and was performed after stylo inoculated with or without LAB was placed for 1 day (delayed filling, DF1) and 2 days (DF2). Results Delayed filling significantly increased pH, buffering capacity, microbial counts and lactic acid, acetic acid and NH3–N contents of stylo prior to ensiling. Inoculating Lb. plantarum SXC48 and CCZZ1 improved the fermentation quality of QF silage, indicated by more lactic acid, as well as lower pH and butyric acid content. Inoculating time significantly affected the pH and lactic acid content of silages. For the DF2 silages, inoculating SXC48 at filling was better than at chopping, while inoculating CCZZ1 had good fermentation quality, regardless of inoculating time. The results of 16S rRNA sequencing indicated that delayed filling enhanced the bacterial diversity of materials and silage, and inoculating significantly changed the composition of silage microbes. Kosakonia, Pseudomonas and Pantoea jointly dominated the fresh material, while Pantoea and Lelliottia jointly dominated the DF2 material. For the QF silages, inoculating SXC48 and CCZZ1 increased the relative abundance of Lactobacillus from 16.4% in the control silage to 76.5% and 82.0%, respectively. Pantoea and Lelliottia jointly dominated the DF silages. Inoculating SXC48 and CCZZ1 also increased the relative abundance of Lactobacillus in the DF stylo silages. Conclusions Under the present research conditions, delayed filling increased the lactic acid content and reduced the acetic acid, propionic acid and NH3–N contents of stylo silage, however, increased the bacterial diversity and relative abundance of undesirable bacteria, such as Pantoea and Lelliottia. The inoculating effectiveness varied with the LAB strains and inoculating time. Inoculating strian SXC48 at filling was better than at chopping, while inoculating strian CCZZ1 at both chopping and filling obtained the similar benefit. Graphical Abstract
Currently, our understanding of the effects of glaucousness on the population sizes of microbial communities on leaf surfaces is limited. The objective of this study was to investigate the influence of glaucousness and chemical composition on the colony-forming unit (CFU) counts of microbes on leaf surfaces. Various leaf morphological and physicochemical features, microbial CFU counts, and glaucousness on the leaf surfaces of wheat (Triticum aestivum var. Shimai No.1), rye (Secale cereale var. Gannong No.1), and triticale (Triticale wittmack var. Gannong No.2) were assessed. The results showed that larger CFU counts of lactic acid bacteria (LAB) and yeasts were found on the non-glaucous leaf surfaces in wheat than on the glaucous leaf surfaces in rye and triticale. The CFU counts of LAB and yeasts were negatively correlated with the amount of soluble wax (P<0.05), and positively correlated with the contents of starch and fructose in leaf tissue (P<0.05), soluble and reduced sugars, soluble protein, and free amino acids on leaf surfaces (P<0.05). The CFU counts of microbes on leaf surfaces were mainly influenced by the level of available carbon sources and glaucousness of leaf surfaces.
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