The effect of a propionic acid bacterial inoculant applied at ensiling on the aerobic stability of wheat and sorghum silages

The effect of a new strain ofPropionibacterium shermanii (PAB), applied at ensiling, on the aerobic stability of wheat and sorghum silages was studied in several experiments under laboratory conditions. In the one experiment with wheat and in those with sorghum a lactic acid bacteria (LAB) inoculant (Lactobacillus plantarum andPediococcus cerevisiae) was also included. After treatment, the chopped forages were ensiled in 1.5-L anaerobic jars which were sampled in triplicate on predetermined dates to follow fermentation dynamics. At the end of the experiments, the silages were subjected to an aerobic stability test. The PAB inoculant improved the aerobic stability only in one experiment with wheat, in which the decrease in pH was very slow; the final pH remained relatively high (4.5). The PAB-treated silages contained 19.5±2.0 g of propionic acid per kg of dry matter. In the experiments with sorghum, the control and PAB-inoculated silages were stable, whereas LAB-inoculated silages deteriorated. The results suggest that PAB can survive in and improve the aerobic stability of only slow-fermenting silages which are prone to aerobic deterioration.     

Manganese as a controlling factor in mixed cultures of Lactobacillus plantarum and enterobacteriaceae

Addition of manganese, at levels of 50 ppm, to a liquid growth medium simulating adverse silage conditions had no effect on the growth or on the fermentation pattern of Enterobacter cloacae and Proteus vulgaris. Yet, the manganese strongly enhanced the growth of Lactobacillus plantarum. Co-cultures of L. plantarum and E. cloacae or P. vulgaris were, by addition of manganese ions, significantly altered in the favour of the former. This finding can be of use in mixed cultures where Enterobacteriaceae act as spoiler microorganisms.     

Isolation of bovine intestinal Lactobacillus plantarum and Pediococcus acidilactici with inhibitory activity against Escherichia coli O157 and F5

Aims:  The growth rate of bovine lactic acid bacteria (LAB) in five different culture conditions, and their inhibitory activity against Escherichia coli O157 and F5 in two assays was assessed to identify LAB for potential prophylactic use in cattle.
Methods and Results:  106 bovine-derived faecal/intestinal LAB were tested in vitro for tolerance to pH 2·0, pH 4·0, 0·15% and 0·3% bile, aerobic incubation, and for inhibitory activity against E. coli O157 ( n  = 3) and F5 ( n  = 1). While no LAB grew at pH 2·0, LAB survivability varied between 35% and 100% on the other tests. Exactly 7·6% (8/106) of LAB supernatants inhibited the growth of E. coli in two assays, whereas 6·6% (7/106) of isolates enhanced the growth of all E. coli strains. Partial 16s rRNA gene sequencing of six best isolates (95th percentile) revealed that five were Lactobacillus plantarum and one Pediococcus acidilactici.
Conclusion:  Lactobacillus plantarum with acid/bile and aerobic resistance and inhibitory activity against E. coli O157 and F5 inhabit the intestinal tract of healthy cattle. Some LAB may enhance E. coli growth.
Significance and Impact of the Study:  Lactobacillus plantarum and P. acidilactici are natural plant micro-organisms and studied silage inoculants. Their identification from gastrointestinal samples of healthy cattle is prophylactically promising.     

Usefulness of length heterogeneity-PCR for monitoring lactic acid bacteria succession during maize ensiling

The use of length-heterogeneity PCR was explored to monitor lactic acid bacteria succession during ensiling of maize. Bacterial diversity was studied during the fermentation of 30-day-old maize in optimal and spoilage-simulating conditions. A length heterogeneity PCR profile database of lactic acid bacteria isolated from the silage and identified by 16S rRNA gene sequencing was established. Although interoperonic 16S rRNA gene length polymorphisms were detected in some isolates, strain analysis showed that most of the lactic acid bacteria species thriving in silage could be discriminated by this method. The length heterogeneity PCR profiles of bacterial communities during maize fermentation were compared with those on a database. Under optimal fermentation conditions all the ecological indices of bacterial diversity, richness and evenness, deduced from community profiles, increased until day thirteen of fermentation and then decreased to the initial values. Pediococcus and Weissella dominated, especially in the first days of fermentation. Lactococcus lactis ssp. lactis and Lactobacillus brevis were mainly found after six days of fermentation. A peak corresponding to Lactobacillus plantarum was present in all the fermentation phases, but was only a minor fraction of the population. Unsuitable fermentation conditions and withered maize leaves in the presence of oxygen and water excess caused an enrichment of Enterococcus sp. and Enterobacter sp.     

微贮用植物乳杆菌固定化菌剂的制备

乳酸菌与纤维素降解菌因其可防止微贮饲料酸败、增加秸秆饲料的营养价值等优点,在秸秆微贮过程中起重要作用。但由于乳酸菌的繁殖会抑制纤维素降解菌的活性,如何实现微贮过程中两种微生物分时发挥功能是解决上述问题的关键。文中利用固定化技术将乳酸菌制备成含有玉米秸秆粉的固定化菌剂以达到缓释的目的。首先制作固定化空白小球得出复合固定化载体成球的最佳浓度,利用玉米芯吸附植物乳杆菌S1得到复合固定化载体,以对S1的包埋率、成球效果等为指标,通过对比两种固定化方法 (包埋法与包埋-交联法),得到固定化植物乳杆菌S1的最佳条件。研究表明,使用6%PVA+0.4%SA+0.3%CMC-Na进行包埋-交联时成球效果最好,使用1.2%SA+0.5%CMC-Na进行直接包埋时成球效果最好。通过对比5种固定化工艺,将1.2%SA+0.5%CMC-Na和吸附玉米粉组成的固定化载体混合物逐滴滴入4%氯化钙中直接包埋24 h得到的固定化小球其机械强度以及包埋率均优于其他工艺。因此,利用玉米芯吸附-海藻酸钠包埋的方法可以有效提高植物乳杆菌包埋效率,为使用固定化技术制备微贮饲料菌剂奠定基础。     

Decoupling the retention time of easily degradable and persistent substances using ultrafiltration membranes increases biogas production yield

The decoupling of the retention time of easily degradable and persistent substances relieves the degradation process from inhibitors and increases the biogas yield. Anaerobic digestion of maize silage was investigated in a pilot‐scale plant with a coupled ultrafiltration membrane. The aim of the study was the evaluation of the influence of the membrane‐based relief of the degradation process and the increase of the retention time of persistent substances. For that purpose, the fermenter content was separated into solid and liquid fractions. The solid fraction was recirculated to the fermenter for longer retention time and higher substrate degradation rates. The fermentation process was improved by the removal of the liquid fraction and adding volatile fatty acids. The results showed an increase of the biogas yield by 7.2% in comparison to the anaerobic digestion without membrane filtration.     

The effects of lactic acid bacteria inoculants and formic acid on the formation of biogenic amines in grass silages

Silages were prepared in six laboratory experiments from four direct-cut grassland swards and pure swards of perennial ryegrass and false oat with dry matter contents ranging between 180 and 325?g/kg. Grass was fermented at 22°C and silages were stored at the same temperature for 4 months. Untreated silages (negative control) and silages preserved with 3?g/kg of formic acid (positive control) were compared with silages inoculated with commercial strains of Lactobacillus plantarum, Lactobacillus buchneri and a mixed preparation Microsil. The inoculants were applied at a dose of 5.10⁶ CFU/g of grass. Seven biogenic amines were extracted from silages with perchloric acid and determined as N-benzamides by micellar electrokinetic capillary chromatography. Common chemical quality parameters of silages were also determined. Tyramine, cadaverine and putrescine were the amines occurring at the highest concentration. As compared to untreated silages, formic acid was most effective to suppress formation of the main amines. Also the inoculants often decreased amine contents significantly (P?相似文献   

Evaluation of the effects of dietary particle fractions on fermentation profile and concentration of microbiota in the rumen of dairy cows fed grass silage-based diets

The study evaluated the effects of three different theoretical particle lengths (TPL) of grass silage on the distribution of particle fractions of the diet and the resulting effects on fermentation profile and concentrations of protozoa and mixed bacterial mass in the rumen of three lactating Holstein cows fed total mixed rations (45% grass silage, 5% grass hay and 50% concentrate) ad libitum. Decreasing TPL of grass silage (long, medium, short) reduced particles retained on the 19-mm sieve of the Penn State Particle Separator, while particle fractions from 8 mm to 19 mm and smaller than 8 mm were increased. Different TPL did not affect pH and the concentration of volatile fatty acids in the rumen. However, lowering the TPL from long to medium increased significantly the bicarbonate concentration, acetate proportion and protozoal number in the rumen, whereas the proportion of bacterial protein in ruminal digesta and its amino acid concentration were significantly increased by the short TPL. For the current feeding conditions, it can be concluded that increasing the fraction of particles between 8 and 19 mm and probably even the fraction below 8 mm by decreasing TPL of grass silage do not adversely affect rumen conditions and can be beneficial in terms of optimising concentration and activity of ruminal microbiota in high-yielding dairy cows.