To develop a silage fermentation technique to adapt to global climate changes, the microbiome and fermentation dynamics of corn silage inoculated with heat-resistant lactic acid bacteria (LAB) under high-temperature conditions were studied. Corn was ensiled in laboratory silo, with and without two selected strains, Lactobacillus salivarius LS358 and L. rhamnosus LR753, two type strains L. salivarius ATCC 11741^T and L. rhamnosus ATCC 7469^T. The ensiling temperatures were designed at 30 °C and 45 °C, and the sampling took place after 0, 3, 7, 14, and 60 days of fermentation. The higher pH and dry matter losses were observed in the silages stored at 45 °C compared to those stored at 30 °C. Silages inoculated with strains LS358 and LR753 at 30 °C had a lower ratio of lactic acid/acetic acid. The dominant bacterial genera gradually changed from Pediococcus and Lactobacillus to Lactobacillus in silages during ensiling at 30 °C, while the bacterial community became more complex and fragmented after 7 d of ensiling at 45 °C. The high temperatures significantly led to a transformation of the LAB population from homo-fermentation to hetero-fermentation. This study is the first to describe microbial population dynamics response to high temperature during corn ensiling, and the results indicate that L. rhamnosus 753 shows potential ability to improve silage fermentation in tropics and subtropics.

To further explore the effects of heterofermentative lactic acid bacteria (LAB) on silage fermentation and aerobic stability, whole-plant corn at around the 1/2 milk-line stage was freshly chopped and ensiled in laboratory silos with deionized water (control), Lactobacillus buchneri (LB), or L. rhamnosus (LR). Each treatment was prepared in triplicate for 3, 14, and 60 d of fermentation, followed by 3 and 7 days of aerobic exposure. The dynamic changes in microbial community were studied by single molecule real-time (SMRT) sequencing. The results showed that the two LAB inoculants altered the microbial communities in different ways. Succession from L. plantarum to L. buchneri and L. rhamnosus was observed in LB- and LR-treated silage, respectively. Both silages improved aerobic stability (82 and 78 h vs. 44 h) by occupying the microbial niche to produce higher levels of acetic acid at terminal fermentation. Because Acetobacter fabarum dominated in the silages after aerobic exposure, beta diversity dramatically decreased. In this study, a. fabarum was reported for the first time in silage and was related to aerobic spoilage. The two heterofermentative LAB produced acetic acid and improved the aerobic stability of the corn silage by occupying the microbial niche at terminal fermentation. Inoculated L. rhamnosus had a greater pH for a longer period of time after opening and less DM loss at day 7.

Wilted (around 35% DM) or un-wilted (around 35% DM) Italian ryegrass treated with three additives (formic acid, FA; Lactobacillus plantarum, LP; Lactobacillus buchneri, LB) was utilized to evaluate the effects of the dry matter (DM) contents on the microbial community and fermentation characteristics, which was ensiled for 60 days in a laboratory-scale silo, followed by 3 days of aerobic exposure. Significantly lower pH and higher lactic acid (LA) contents were observed in the LP-treated group ensiled at both DM contents (differences were significant when p < 0.05). The contents of LA, acetic acid (AA), numbers of lactic acid bacteria (LAB) and ammonia nitrogen (NH₃-N) in the FA-treated group were significantly lower than those in other treatments (p < 0.05). L. buchneri was the dominant bacteria after 60 days fermentation, while Enterobacteria became prevalent after 3 days of aerobic exposure. L. buchneri was found in the LB-treated group with higher acetic acid. Although the best fermentation quality was observed in the LP-treated silages, the aerobic stability was lowest compared to other groups (p < 0.05). In conclusion, our findings suggest that the DM content of Italian ryegrass affected its epiphytic microbial community and the effectiveness of the different type of additives. Formic acid was more suitable for un-wilted Italian ryegrass silage, L. plantarum had a better effect in wilted Italian ryegrass silage, and L. buchneri prolonged the aerobic stability of Italian ryegrass. DM content and purpose of ensiling should be the key factors for choosing different types of additives for Italian ryegrass silage.

Background: Elymus L. is the largest genus in the Triticeae tribe. Most species in this genus are highly stress resistant, with excellent forage value. Elymus breviaristatus, a rare species endemic to the Qinghai-Tibet Plateau (QTP), is declining due to habitat fragmentation. However, genetic data for E. breviaristatus are limited, with expressed sequence tag (EST) markers being particularly rare, hampering genetic studies and protection measures. Results: We obtained 9.06 Gb clean sequences from the transcriptome of E. breviaristatus, generating 171,522 unigenes, which were assembled and functionally annotated against five public databases. We identified 30,668 SSRs in the E. breviaristatus transcriptome, from which 103 EST-SSR primer pairs were randomly selected. Of these, 58 pairs of amplified products of the expected size, and 18 of the amplified products were polymorphic. Model-based Bayesian clustering, the unweighted pair group method with arithmetic average (UPGMA), and principal coordinate analysis (PCoA) of 179 wild E. breviaristatus in 12 populations using these EST-SSRs were generally consistent, grouping the 12 populations into two major clades. Analysis of molecular variance (AMOVA) found 70% of the genetic variation among the 12 populations and 30% within the populations, indicating a high level of genetic differentiation (or low gene exchange) among the 12 populations. The transferability of the 58 successful EST-SSR primers to 22 related hexaploid species was 86.2–98.3%. UPGMA analysis generally grouped species with similar genome types together. Conclusions: Here, we developed EST-SSR markers from the transcriptome of E. breviaristatus. The transferability of these markers was evaluated, and the genetic structure and diversity of E. breviaristatus were explored. Our results provide a basis for the conservation and management of this endangered species, and the obtained molecular markers represent valuable resources for the exploration of genetic relationships among species in the Elymus genus.

To investigate the characteristics of different LAB strains isolated from subtropics and their effects on Napier grass (Pennisetum purpureum Schum.) silage with two dry matter levels, sugar fermentation pattern and growth profiles of three screened lactic acid bacteria (LAB) strains [Pediococcus pentosaceus (PP04), Weissella cibaria (WC10), and Lactobacillus plantarum (LP694)] were characterized, and then used either individually or in combination at 1.0 × 10⁶ cfu·g⁻¹ fresh weight to inoculate grass having 15% or 25% dry matter (DM). Treatments were applied: 1) no inoculant (control); 2) PP04; 3) WC10; 4) LP694; 5) M-1 (PP04: WC10 = 2:1); 6) M-2 (PP04: LP694 = 1:2); 7) M-3 (WC10: LP694 = 2:1); 8) M-4 (PP04: WC10: LP694 = 2:1:1). The results showed that all inoculations increased LAB, DM recovery, and lactic acid concentration, while decreasing pH, the ammonia nitrogen/total nitrogen (NH₃-N/TN), and butyric acid concentration compared to control group in both DM. However, the effect of inoculations was very limited at 15% DM. Silages with inoculants achieved higher silage quality at 25% DM than 15% DM. The different LAB inoculants result in significant differences in silage quality while W. cibaria decreased the pH and inhibited the growth of undesirable bacteria and those characteristics were not affected by the DM content.

Introduction: Weak aerobic stability is a notable challenge for whole-plant corn silage, particularly in hot and humid regions. Acetobacter is commonly regarded as an indicator of aerobic deterioration in silage, yet its precise role in fermentation and during aerobic exposure, as well as the factors that promote its growth, remain insufficiently understood.Methods: In this study, whole-plant corn silage was prepared using a bagged method with controlled dry matter (DM) content at 20%, 25%, and 30%, and initial concentrations of A. pasteurianus at 40%, 50%, and 60%. The silage was stored for 60 days under varying temperatures (20°C, 30°C, and 40°C). Following the anaerobic storage phase, the silage was exposed to air at room temperature (20-25°C) for 7 days, both with and without A. pasteurianus inoculation.Results: The results demonstrated that A. pasteurianus did not impact the nutritional value of the silage during anaerobic fermentation, maintaining a low pH (< 3.80). However, during aerobic exposure, the presence of A. pasteurianus significantly reduced the aerobic stability of the silage. The microbial community shifted from primarily Klebsiella species initially to Lactobacillus and Acetobacter species post-ensiling. During the aerobic exposure phase, A. pasteurianus and A. fabarum became the dominant species. Response Surface Methodology (RSM) analysis identified optimal conditions for the proliferation of A. pasteurianus during the aerobic phase, which occurred at 28°C, 25% DM, and 52% initial concentration at 3 ml/kg.Discussion: These findings confirm that A. pasteurianus plays a critical role in reducing the aerobic stability of whole-plant corn silage. Additionally, the study identifies the optimal conditions that favor the proliferation of A. pasteurianus, offering valuable insights for the development of strategies to prevent and control this bacterium, thereby improving the aerobic stability of silage in hot and humid regions.