Inclusion of abandoned rhubarb stalk enhanced anaerobic fermentation of alfalfa on the Qinghai Tibetan Plateau

Epiphytic microbiota source stimulates the fermentation profile and bacterial community of alfalfa-corn mixed silage

The epiphytic microbiota source on plants plays a crucial role in the production of high-quality silage. To gain a better understanding of its contribution, the microbiota of alfalfa (M1C0), corn (M0C1) and the resulting mixture (M1C1) was applied in alfalfa-corn mixed silage production system. M1C0 decreased ammonia-N levels in terms of total nitrogen (57.59-118.23 g/kg TN) and pH (3.59-4.40) values (p < 0.01), which increased lactic acid (33.73-61.89 g/kg DM) content (p < 0.01). Consequently, this resulted in higher residual water-soluble carbohydrate (29.13-41.76 g/kg DM) and crude protein (152.54-167.91 g/kg DM) contents, as well as lower NDF (427.27 g/kg DM) and ADF (269.53 g/kg DM) contents in the silage compared to M1C1- and M0C1-treated samples. Moreover, M1C0 silage showed significantly higher bacterial alpha diversity indices (p < 0.05), including the number of observed species and Chao1 and Shannon diversity indices, at the later stages of ensiling. Lactobacillus, Kosakonia and Enterobacter were the dominant bacterial species in silages, with a relative abundance of >80%. However, the abundance of Lactobacillus amylovorus in M0C1- and M1C1-treated silage increased (p < 0.01) in the late stages of ensiling. These findings confirmed that the epiphytic microbiota source exerts competitive effects during anaerobic storage of alfalfa-corn mixed silage.

Contribution of the bacterial community of poorly fermented oat silage to biogas emissions on the Qinghai Tibetan Plateau

To better utilize poorly fermented oat silage on the Qinghai Tibetan Plateau, 239 samples of this biomass were collected from the plateau temperate zone (PTZ), plateau subboreal zone (PSBZ), and nonplateau climatic zone (NPCZ) in the region and analyzed for microbial community, chemical composition and in vitro gas production. Climatic factors affect the bacterial α-diversity and β-diversity of poorly fermented oat silage, which led to the NPCZ having the highest relative abundance of Lactiplantibacillus plantarum. Furthermore, the gas production analysis showed that the NPCZ had the highest maximum cumulative gas emissions of methane. Through structural equation modeling analysis, environmental factors (solar radiation) affected methane emissions via the regulation of lactate production by L. plantarum. The enrichment of L. plantarum contributes to lactic acid production and thereby enhances methane emission from poorly fermented oat silage. Notably, there are many lactic acid bacteria detrimental to methane production in the PTZ. This knowledge will be helpful in revealing the mechanisms of environmental factors and microbial relationships influencing the metabolic processes of methane production, thereby providing a reference for the clean utilization of other poorly fermented silage.

Effects of exogenous lactic acid bacteria and maize meal on fermentation quality and microbial community of Orychophragmus violaceus silage

Orychophragmus violaceus is a local Brassicaceae in China, while most of it is directly mowed and discarded after the ornamental period. In order to develop forage resources, this study firstly evaluated the potential preservation of O. violaceus silage. O. violaceus was harvested at full-bloom stage, and ensiled without (CK) or with maize meal (Y5), lactic acid bacteria inoculant (Z) and compound additive (Y5Z) for 60 d. Results of chemical and microbiological analysis showed that a large amount of lactic acid was produced and the final pH value was below 4.1 in silages regardless of additive application. CK silage was well preserved as indicated by the low levels of dry matter loss and butyric acid content, and the predominant genus were identified as Enterococcus and Pediococcus. Y5 silage had potential health risks for humans and animals as seen by frequent occurrence of pathogenic bacteria Clostridium and Achromobacter. Z and Y5Z silages were poorly preserved, resulting in great dry matter loss and butyric acid content. Considering the abundant acetic acid production, the dominant Lactobacillus might possess a heterofermentative pathway in Z and Y5Z silages. In conclusion, O. violaceus has the potential to be long stored as silage because of its sufficient water-soluble carbohydrates, while exogenous lactic acid bacteria and maize meal generally provided little positive effect. In future research, efficient homofermentative Lactobacillus strains were suggested to be screened to further enhance the ensiling process of O. violaceus silage.

Potential for volatile fatty acid production via anaerobically-fermenting rice straw pretreated with silage effluent and phenyllactic acid

To resolve environmental problems associated with rice straw and silage effluent disposal, silage effluent pretreating rice straw for the anaerobic production of volatile fatty acids (VFAs) was investigated. To prevent the lactic acid bacteria in silage effluent from inhibiting anaerobic fermentation, four phenyllactic acid (PLA) levels were set (0, 0.1, 0.3, 0.5 mg/kg). The total VFA yields of treatments pretreated only with silage effluent (CK) were higher than the groups combined with PLA during 15 days fermentation. Compared to PLA treatments, the total VFA of CK increased by 11.4 % ∼ 25.1 % on day 15. The CK showed higher lactic and propionic acid contents and lower pH values (<4.9). The PLA treatments decreased Lactobacillus abundance while increasing bacterial richness and evenness, and acetic and butyric acid contents. These demonstrated silage effluent has the potential to be used as a biological pretreatment for VFA production in anaerobic fermentation.

Exploring the bacterial community succession and metabolic profiles of Lonicera japonica Thunb. residues during anaerobic fermentation

Discarding Lonicera japonica Thunb. (LJT) residues containing many active metabolites create tremendous waste. This study aimed to effectively use LJT residues by anaerobic fermentation. Fermentation significantly decreased the pH values and reduced the abundance of undesirable bacteria (potential pathogenic and biofilm-forming) while increasing Lactobacillus abundance. Compound additive use further improved fermentation quality (significantly increased the lactic acid (LA) content and decreased the pH values and ammonia nitrogen (a-N) content) and nutrient quality (significantly decreased the acid detergent fiber (ADF) content and increased the water-soluble carbohydrate (WSC) content) and optimized the microbial community (increased the Lactobacillus abundance). Fermentation also altered the flavonoids, alkaloids and phenols contents in the residues with minor effects on the functional metabolites amounts. The LJT residues metabolic profile was mainly attributed to its epiphytic bacteria, with a small contribution from the compound additive. Thus, compound additives may improve anaerobic LJT residue fermentation without functionally impairing the metabolites.

Preservation characteristics and bacterial communities of crimped ensiled barley grains modulated by moisture content and additive application

Information about the relationships between preservation characteristics and main bacterial communities of fermented feeds can guide decision making during feed preservation and silage additive development. The objective was to evaluate fermentation quality, aerobic stability, microbial quality and bacterial profile of crimped barley grains ensiled under three moisture contents (MC): 228 (low MC), 287 (medium MC) and 345 (high MC) g/kg fresh matter; and using four additive treatments: 1. Control (CONT), 2. Formic and propionic acid-based additive (FPA), 3. Inoculation with homofermentative and heterofermentative strains of lactic acid bacteria (LAB), and 4. Salt-based additive (SALT). There was a quadratic effect (p < 0.05) of incremental MC on pH where greater decline happened from low (5.81) to medium (4.83) MC than from medium to high (4.28) MC, while lactic acid concentration and aerobic stability increased in a linear manner (p < 0.05). Ammonia-N and acetic acid concentrations increased quadratically (p < 0.05) with increasing levels of MC. The effects of additives depended on MC so that improvements in preservation characteristics in response to LAB and SALT were observed at medium and high MC, while FPA was effective at all MC levels. A minor shift was observed in bacterial ecology from raw material towards low MC samples, with Erwiniaceae sp., Enterobacterales spp. and Pseudomonas dominating the fermentation. A major change occurred in medium and high MC materials, where Fructilactobacillus dominated the fermentation in CONT, FPA and SALT silages. LAB-treated silages at medium and high MC resulted in a distinguished pattern with dominance of Lentilactobacillus followed by Lactiplantibacillus. Most abundant communities in the samples, such as Fructilactobacillus, Erwiniaceae sp., Enterobacterales spp. and Pseudomonas, were correlated with several fermentation characteristics. Our results showed that crimped barley grains could be successfully ensiled under various MC and additive treatments. Low MC feeds had higher risk to be aerobically unstable while high MC resulted in more extensive fermentation, with potentially poor fermentation quality. The suitable additive depends on the raw material characteristics as LAB and SALT require relatively high MC to be effective, while FPA showed consistent improvements over all MC levels used in the current study. Awareness of the MC of grain prior to ensiling allows to identify the risks to preservation quality and provides information for choosing an effective additive.

Fermentation quality and bacterial ecology of red clover dominated silage modulated by different management factors

Identification of bacterial communities in both the raw material and the subsequent silages provides new insights into understanding the silage fermentation process. The objective was to evaluate how different silage management factors affect silage preservation characteristics, the microbiome, and their correlations. A red clover dominated sward was used as the raw material and ensiled in pilot scale using a 3 × 4 design, with three management conditions including the level of compaction (loose and tight), and further, for the tightly compacted silages contamination with soil and faeces was conducted; and four different additive treatments with different modes of action: Control without additive (CONT), formic and propionic acid-based additive (FPA), homofermentative lactic acid bacteria inoculant (LAB) and salt-based additive (SALT). Samples of the raw material and subsequent silages were taken and routinely analysed, including DNA extraction and PCR amplification using universal primers. Tight compaction reduced slightly the extent of silage fermentation, but contamination with soil and faeces stimulated a non-desired type of fermentation with higher concentrations of ethanol, acetic acid and propionic acid and a higher pH. Use of LAB and SALT had only minimal effects on silage fermentation, but FPA clearly restricted fermentation and resulted in a better fermentation quality (lower pH, ammonia N and acetic acid concentration) of the silages compared to CONT. The FPA silages presented greater diversity of bacterial communities compared to the other silages. Proteobacteria were the most abundant in raw material, followed by Firmicutes, and major shifts happened in these communities during the silage fermentation process. Weissella was found in small amounts in the raw material but it dominated in the silages. The most abundant communities in the silages, such as Weissella, Lactobacillus and Pseudomonas, were correlated with several silage fermentation characteristics. Use of FPA improved fermentation quality of silages, but SALT and LAB differed from CONT to a smaller extent. All additives modified the bacterial profiles of grasses ensiled under different management conditions. The combination of parameters related to silage quality and bacterial communities provided a deeper understanding of the silage fermentation process and how they can be manipulated to obtain better feed quality.

Fermentation quality, bacterial community, and predicted functional profiles in silage prepared with alfalfa, perennial ryegrass and their mixture in the karst region

There is little information regarding the dynamics of fermentation products and the bacterial community in silage prepared with alfalfa (MS), perennial ryegrass (LP), and their mixture in the karst region. In this study, we explored the effects of combining MS with LP in different ratios (100% MS, 70% MS + 30% LP, 50% MS + 50% LP, 30% MS + 70% LP and 100% LP; fresh matter basis) on silage chemical composition, fermentation quality, bacterial communities and predicted functions during the ensiling process. Each treatment was prepared in triplicate and stored at room temperature (22–25°C) for 7, 15, and 45 days. The dry matter (DM) and water-soluble carbohydrate content of the silages increased as the LP proportion in the mixed silage increased; at 45 days, the 70% MS + 30% LP, 50% MS + 50% LP and 30% MS + 70% LP silages contained higher (p &lt; 0.05) CP content than the 100% MS and 100% LP silages. The 30% MS + 70% LP and 100% LP silages exhibited lower (p &lt; 0.05) pH and higher (p &lt; 0.05) LA content than the other silages; at 45 days, none of the silages contained PA or BA. As fermentation proceeded, the abundance of harmful (Enterobacteriaceae and Sphingomonas) and beneficial (Lentilactobacillus, Lactiplantibacillus, Secundilactobacillus, and Levilactobacillus) microorganisms decreased and increased, respectively, as the LP proportion in the mixed silage increased. The predicted functional distribution of microbial communities and metabolic pathways revealed that the 30% MS + 70% LP and 100% LP silages had a stronger capacity for fermentation and a weaker capacity for nitrate reduction than the other silages. Moreover, as the fermentation proceeded, the 30% MS + 70% LP and 100% LP treatments enhanced the functions of “Metabolism,” “Genetic information processing” and “Organismal systems” at level 1, the functions of “Amino acid metabolism” and “Nucleotide metabolism” at level 2, and the functions of “Metabolic pathways,” “Biosynthesis of secondary metabolites,” “Biosynthesis of antibiotics” and “Purine metabolism” at level 3. Thus, adding LP could improve the fermentation quality of MS silage by changing the composition and metabolic function of microbes; furthermore, ensiling 30% alfalfa with 70% ryegrass can produce high-quality silage in the karst region.

Effect of different organic acid additives on the fermentation quality and bacterial community of paper mulberry (Broussonetia papyrifera) silage

To investigate the effects of different organic acid additives and their concentrations on the fermentation quality and bacterial community of paper mulberry silage, paper mulberry was left untreated (control) or was treated with ethylenediaminetetraacetic acid (EDTA), propionic acid (PA) or citric acid (CA), the amount of each additive was 2 g.kg^-1 FM, 5 g.kg^-1 FM and g.kg^-1 FM. All groups were ensiled for 3, 7, 15, 30 and 60 days. Compared to the control, adding EDTA reduced protein breakdown, preserved more water-soluble carbohydrates of the silages (WSCs, 24.74 g.kg^-1 DM), and high concentrations of EDTA inhibited the activity of undesirable microorganisms. Adding PA increased the abundance of Lactiplantibacillus and decreased the abundance of Enterococcus, and it caused a rapid decrease in the pH of the silage at an early stage (from 6.50 to 5.31) while altering the microbiota, and low concentrations of PA resulted in high LA (66.22 g.kg^-1 DM) concentration and low PA (9.92 g.kg^-1 DM) concentration at 60 days of ensiling. Different concentrations of additives altered the microbial community of paper mulberry to different degrees. High concentrations of PA and CA can increase the abundance of Lactiplantibacillus. High concentrations of CA resulted in a rapid decrease in silage pH at an early stage and higher WSC concentration. These results suggest that EDTA, PA and CA can be used as additives to improve the quality of paper mulberry silage.

Effect of lactic acid bacteria, yeast, and their mixture on the chemical composition, fermentation quality, and bacterial community of cellulase-treated Pennisetum sinese silage

The present study investigated the effects of Lentilactobacillus buchneri, Saccharomyces cerevisiae, and a mixture of the two on the cellulose degradation and microbial community of cellulase-treated Pennisetum sinese (CTPS) during biological pretreatment. The CTPS was stored without additives (CK) or with L. buchneri (L), yeast (Y, S. cerevisiae), and their mixture (LY) under anaerobic conditions for 60 days. All inoculants enhanced the anaerobic fermentation of CTPS. In relative to L, inoculations with Y and LY decreased the cellulose level of fermented-CTPS by 8.90 ~ 17.13%. Inoculation with L inhibited the growth of Weissella cibaria during anaerobic storage. However, inoculations with LY increased the relative abundance of the homofermentative bacterium Lactiplantibacillus plantarum by 6.04%. Therefore, inoculating S. cerevisiae reduced the adverse effects of L. buchneri-stimulated fermentation on cellulose degradation by altering the bacterial community during anaerobic storage of P. sinese. This work provides a new insight for the subsequent anaerobic digestion of P. sinese.

Effect of cellulase and lactic acid bacteria on the fermentation quality, carbohydrate conversion, and microbial community of ensiling oat with different moisture contents

Oat (Avena sativa L.) is one of the most widely cultivated crops used as forage. The aim of this study was to evaluate the effects of cellulase and Lactobacillus plantarum interactions with different moisture contents on oat ensiling. Oats with three moisture contents were treated with nothing (C), cellulase (CE), lactic acid bacteria (LP), or CE+LP and ensiled for 30 and 60 days. Compared with the control, LP and CE treatments increased crude protein and lactic acid concentrations and reduced the pH and ammonia nitrogen/total nitrogen (NH₃-N/TN) ratios of silages. The addition of CE improved lignocellulosic degradation, compared with approximately 67% (LD) and 81% moisture content (HD) ensiling, CE (CE, CE+LP) ensiling in the approximately 75% moisture content (MD) group retained higher water-soluble carbohydrate, glucose, sucrose and fructose concents. The LP and CE inoculations significantly reduced the microbial community diversity, and lower values for the observed species, ACE, Chao1, and Shannon indices compared with CK-treated samples. Additives inhibited the growth of unfavorable bacteria (such as Clostridium) and increased the abundances of lactic acid bacteria (LAB); the maximum increases in the Lactiplantibacillus abundance were obtained in the LP- and CE+LP-treated samples, improving the microbial community structure in silage. In summary, adding LP and CE effectively improved the oat fermentation quality, and better performances in ensiling oat and lignocellulose degradation were obtained with LP and CE combinations, especially for the MD group of silages that were ensiled for 60 days. The addition of CE and LP at the appropriate moisture content might be helpful for producing high-quality oat silage, and also provide a simple and feasible method to enhance the effects of bacteria and enzymes.

Innovative utilization of herbal residues: Exploring the diversity of mechanisms beneficial to regulate anaerobic fermentation of alfalfa

In order to increase the utilization of herbal residues, realize efficient utilization of resources, the bacterial community and anaerobic fermentation characteristics of alfalfa ensiling treated with 36 kinds of herbal residues were studied. All the herbal residues improved the anaerobic fermentation quality in different degrees, indicated by lower pH, NH₃-N and butyric acid concentrations. However, the contents of lactic and acetic acids varied widely in silage with different herbal residues. Pearson's correlation analysis showed that the improved fermentation quality was closely associated with the variation of lactic acid bacteria community. Consequently, the herbal residues could improve anaerobic fermentation quality by stimulating desirable Lactobacillus species and inhibiting undesirable microbes. This study provides new insights for efficient utilization of herbal residues.

Effect of Amomum villosum essential oil as an additive on the chemical composition, fermentation quality, and bacterial community of paper mulberry silage

Paper mulberry (Broussonetia papyrifera L., PM) is being used as a new type of animal protein feed to address the feed crisis. To investigate the effect of additives on the chemical composition, fermentation quality, and bacterial community of PM silage (at room temperature, 25°), paper mulberry was fermented with formic acid (FA), Amomum villosum essential oil (AVEO) and lactic acid bacteria (LAB) inoculant treatments. The results showed that fresh PM had a low water-soluble carbohydrate (WSC) content and large amounts of unclassified bacteria. Compared with the CK and LAB treatments, the FA and AVEO treatments significantly (P &lt; 0.05) decreased the pH and increased the lactic acid content of PM silage after 60 days of ensiling. In the AVEO-treated silages the abundance of Lactococcus in the early stage of ensiling increased by 14.09%, the abundances of Levilactobacillus and Lentilactobacillus in the late stage of ensiling increased by 58.34 and 91.12%, respectively, and the abundance of Stenotrophomonas decreased by 94.71%, resulting in improved PM silage quality. These results confirmed that AVEO could potentially be developed as a new additive for improving the fermentation quality of silage.