The present study investigated the species level based microbial community and metabolome in corn silage inoculated with or without homofermentative
and heterofermentative
using the PacBio SMRT ...Sequencing and time-of-flight mass spectrometry (GC-TOF/MS). Chopped whole crop corn was treated with (1) deionized water (control), (2)
, or (3)
. The chopped whole crop corn was ensiled in vacuum-sealed polyethylene bags containing 300 g of fresh forge for 90 days, with three replicates for each treatment. The results showed that a total of 979 substances were detected, and 316 different metabolites were identified. Some metabolites with antimicrobial activity were detected in whole crop corn silage, such as catechol, 3-phenyllactic acid, 4-hydroxybenzoic acid, azelaic acid, 3,4-dihydroxybenzoic acid and 4-hydroxycinnamic acid. Catechol, pyrogallol and ferulic acid with antioxidant property, 4-hydroxybutyrate with nervine activity, and linoleic acid with cholesterol lowering effects, were detected in present study. In addition, a flavoring agent of myristic acid and a depression mitigation substance of phenylethylamine were also found in this study. Samples treated with inoculants presented more biofunctional metabolites of organic acids, amino acids and phenolic acids than untreated samples. The
species covered over 98% after ensiling, and were mainly comprised by the
and
. As compared to the control silage, inoculation of
increased the relative abundances of
and
, and a considerable decline in the proportion of
was observed; whereas an obvious decrease in
and increases in
and
were observed in the
inoculated silage. Therefore, inoculation of
and
regulated the microbial composition and metabolome of the corn silage with different behaviors. The present results indicated that profiling of silage microbiome and metabolome might improve our current understanding of the biological process underlying silage formation.
•Cholesterol-lowering effects of LAB isolates from yak yoghurt were investigated.•L. plantarum LP3 was screened out due to its high cholesterol-lowering activity.•The strain exhibited an excellent ...tolerance to simulated GI tract.•It effectively alleviated the hyperlipidemia in rats fed a high-cholesterol diet.•The strain could be a potential probiotics to be used in functional food.
The objectives of the present study were to screen cholesterol-lowering lactic acid bacteria from traditional fermented Tibetan yak milk, and to evaluate their potential use as cholesterol-reducing probiotics in rats. A total of 115 isolates were evaluated for their cholesterol-lowering and probiotic profiles by in vitro assays, and a strain with good performance in in vitro test was selected to test its probiotic effects in rats fed a high cholesterol diet. Results showed that the strain of L. plantarum Lp3 had a high cholesterol-reducing rate (73.3%) and survival rate in simulated gastrointestinal fluids. Administration of Lp3 to rats fed a high-cholesterol diet promoted notable declines in serum and liver cholesterol and triglycerides levels, and reduced lipid deposition in the cytoplasm of rat’s liver tissue. These results suggest that the strain of L. plantarum Lp3 could be a potential probiotic to treat hyperlipidemia and to be used in functional food.
•Antioxidant properties of LAB stains isolated from yak yogurt were investigated.•Screened strain of L. delbrueckii F17 had high free radical scavenging activity.•L. delbrueckii F17 exhibited ...excellent tolerance to simulated GI tract.•L. delbrueckii F17 effectively alleviated the oxidative stress of ageing mice.•The strain could be applied as a potential antioxidant strain in functional food.
This study investigated the antioxidant properties of lactic acid bacteria (LAB) isolated from spontaneously fermented yak milk collected on the Tibetan Plateau. Nine different species of LAB strains with high 2,2-diphenyl-1picrylhydrazyl radical-scavenging activity were screened from 403 isolates, and most of the selected LAB strains exhibited higher antioxidant activity than the reference strains from low-altitude areas. Among the 9 screened strains, L. delbrueckii subsp. bulgaricus F17 showed the greatest probiotic potential due to its high free radical scavenging activity (scavenging 59% OH and 54% O2−) and high survival rate (58%) within a simulated gastrointestinal tract. After administering the strain to ageing mice induced by d-galactose, the glutathione peroxidase activity in mouse livers and sera and the superoxide dismutase activities in mouse sera and brains increased significantly, while malondialdehyde levels in mouse livers and sera decreased significantly. This unique isolate could be considered a potential antioxidant strain for functional food production.
The aim of this study was to evaluate the effect of two organic acids malic acid (MA) and citric acid (CA), Lactobacillus plantarum (LP) and their mixtures on the fermentation of alfalfa silage. The ...wilted and chopped alfalfa was ensiled in vacuum-sealed plastic bags (200-230 g per bag) with following additives: 0.5% distilled water (control), 0.5% DL-MA, 0.5% CA, LP (1 · 10
6
cfu/g), 0.5% DL-MA plus LP (MA+LP) or 0.5% CA plus LP (CA+LP) (application rates based on fresh weight). Each treatment had four replicates and was stored at room temperature. After 60 d of ensiling, decreases in pH, non-protein N (NPN) and increases in lactic acid were observed in all additive-treated silages (p < 0.01). Compared with treatment LP, higher pH and lower lactic acid concentrations were observed after MA or CA addition (p < 0.05) and further application of MA or CA together with LP did not promote lactic acid fermentation in ensiled alfalfa. Furthermore, additives decreased the proportion of saturated fatty acids and increased the proportion of polyunsaturated fatty acids in ensiled alfalfa, with the highest level in CA-treated silages (p < 0.05). Although MA and CA were not as effective as LP in improving silage fermentation quality, treatments MA+LP and CA+LP were more effective in decreasing silage NPN, and CA was most effective in inhibiting biohydrogenation of fatty acids in ensiled alfalfa.
Effects of different chemical additives on peptide composition in ensiled alfalfa (Medicago sativa L.) were investigated by using gel filtration and determination of N characteristics. The alfalfa ...silages were prepared untreated (control) or with formic acid, formaldehyde or tannic acid as additives at ensiling. All additives reduced non‐protein N (NPN), ammonia nitrogen (NH3‐N) and amino acid N (AA‐N) in the ensiled forage, and the most effective reduction of NPN and AA‐N was observed in the formaldehyde‐treated silages. Peptides in the control silage were mainly dipeptides to peptides with five amino acid residues. Most peptides in the formic acid‐treated silage contained 4–12 amino acid residues. Although most peptides in the formaldehyde‐treated silages contained 4–6 amino acid residues, there was a considerable proportion of peptides with 7–11 amino acid residues. Tannic acid had little effect on peptide size of ensiled alfalfa extract in which most peptides contained 5–6 amino acid residues. Peptide size in formic acid‐treated alfalfa silage was greater than that in the other treatments. Addition of formic acid and formaldehyde not only increased the peptide concentration in alfalfa silage, but enlarged the peptide size.
Hot stamping is an effective method to improve both the elongation and plasticity of ultra-high-strength steels and thus a higher specific strength can be achieved, making weight reduction in motor ...vehicles possible. However, due to the die temperature rise and the cooling liquid within hot stamping applications, the friction in its forming stage is always a nonisothermal mode. Therefore, a high-temperature slider-on-sheet strip (SOSS) tribotester to simulate sliding friction in hot stamping of 22MnB5 hot stamping steel sheet was designed and custom-made. Then, it was employed to exploit the high-temperature friction behavior and mechanism of bare 22MnB5 hot-stamped boron steel sheets under different die temperatures and extra cooling conditions. Results show that the friction coefficient obtained under the pure die cooling conditions is lower than that obtained under extra cooling conditions, which is attributed to the formation of thicker oxide layers on the surface of specimen during the cooling process. In addition, the friction coefficient is obviously decreased when the die temperature is increased to 200 °C, which is ascribed to the co-action of the destruction of the oxide layers and the formation of bainite.
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