The reconstitution mechanism of napier grass microiota during the ensiling of alfalfa and their contributions to fermentation quality of silage

Utilisation of Lactiplantibacillus plantarum and propionic acid to improve silage quality of amaranth before and after wilting: fermentation quality, microbial communities, and their metabolic pathway

Objective

The aim of this study was to investigate the effects of Lactiplantibacillus plantarum (L. plantarum) and propionic acid (PA) on fermentation characteristics and microbial community of amaranth (Amaranthus hypochondriaus) silage with different moisture contents.

Methods

Amaranth was harvested at maturity stage and prepared for ensiling. There were two moisture content gradients (80%: AhG, 70%: AhS; fresh material: FM) and three treatments (control: CK, L. plantarum: LP, propionic acid: PA) set up, and silages were opened after 60 d of ensiling.

Results

The results showed that the addition of L. plantarum and PA increased lactic acid (LA) content and decreased pH of amaranth after fermentation. In particular, the addition of PA significantly increased crude protein content (p < 0.05). LA content was higher in wilted silage than in high-moisture silage, and it was higher with the addition of L. plantarum and PA (p < 0.05). The dominant species of AhGLP, AhSCK, AhSLP and AhSPA were mainly L. plantarum, Lentilactobacillus buchneri and Levilactobacillus brevis. The dominant species in AhGCK include Enterobacter cloacae, and Xanthomonas oryzae was dominated in AhGPA, which affected fermentation quality. L. plantarum and PA acted synergistically after ensiling to accelerate the succession of dominant species from gram-negative to gram-positive bacteria, forming a symbiotic microbial network centred on lactic acid bacteria. Both wilting and additive silage preparation methods increased the degree of dominance of global and overview maps and carbohydrate metabolism, and decreased the degree of dominance of amino acid metabolism categories.

Conclusion

In conclusion, the addition of L. plantarum to silage can effectively improve the fermentation characteristics of amaranth, increase the diversity of bacterial communities, and regulate the microbial community and its functional metabolic pathways to achieve the desired fermentation effect.

The gain effect of microbial consortia induced by adaptive domestication for efficient conversion of Chinese cabbage waste by anaerobic fermentation

The resource-based treatment of Chinese cabbage waste by anaerobic fermentation can effectively mitigate air, soil, and groundwater pollution. However, the compatibility between fermentative microorganisms and the environment might be a crucial limiting factor for the resource recycling of Chinese cabbage waste. Therefore, the gain effect of microbial consortia (JMRS, JMRST, JMRSZ, JCCW, JCCWT and JCCWZ) induced by adaptive domestication for efficient conversion of Chinese cabbage waste by anaerobic fermentation were explored in this study. A total of 42 single subsamples with same weights were randomly divided into seven treatments: sterile deionized water (Control); anaerobic fermentation inoculated with JMRS (MRS); anaerobic fermentation inoculated with JMRST (MRST); anaerobic fermentation inoculated with JMRSZ (MRSZ); anaerobic fermentation inoculated with JCCW (CCW); anaerobic fermentation inoculated with JCCWT (CCWT); anaerobic fermentation inoculated with JCCWZ (CCWZ) and samples were taken on days 30 and 60 after anaerobic fermentation. The results exhibited that all the treatments contributed to high levels of lactic acid (178.77-201.79 g/kg dry matter) and low levels of ammonia-N (12.99-21.03 g/kg total nitrogen). Meanwhile, MRSZ enhanced (p < 0.05) acetic acid levels (1.53 g/kg dry matter) and resulted in the lowest yeast counts. Microbiologically, the addition of microbial consortia decreased the linear discriminant analysis (LDA) scores of Massilia and Stenotrophomonas maltophilia. Moreover, MRSZ enriched (p < 0.05) Lactobacillus hilgardii, and decreased (p < 0.05) the abundance of bacteria containing mobile elements and potentially pathogenic bacteria. In conclusion, JMRSZ improved the efficient conversion of Chinese cabbage waste for resource utilization.

Characterization of phyllosphere endophytic lactic acid bacteria reveals a potential novel route to enhance silage fermentation quality

The naturally attached phyllosphere microbiota play a crucial role in plant-derived fermentation, but the structure and function of phyllosphere endophytes remain largely unidentified. Here, we reveal the diversity, specificity, and functionality of phyllosphere endophytes in alfalfa (Medicago sativa L.) through combining typical microbial culture, high-throughput sequencing, and genomic comparative analysis. In comparison to phyllosphere bacteria (PB), the fermentation of alfalfa solely with endophytes (EN) enhances the fermentation characteristics, primarily due to the dominance of specific lactic acid bacteria (LAB) such as Lactiplantibacillus, Weissella, and Pediococcus. The inoculant with selected endophytic LAB strains also enhances the fermentation quality compared to epiphytic LAB treatment. Especially, one key endophytic LAB named Pediococcus pentosaceus EN5 shows enrichment of genes related to the mannose phosphotransferase system (Man-PTS) and carbohydrate-metabolizing enzymes and higher utilization of carbohydrates. Representing phyllosphere, endophytic LAB shows great potential of promoting ensiling and provides a novel direction for developing microbial inoculant.

Responses of microbial community dynamics, co-occurrences, functional shifts, and natural fermentation profiles of Elymus nutans silage to altitudinal gradients

IMPORTANCE

On the Qinghai-Tibet Plateau (QTP), feed shortages are common due to cold environmental conditions and the short growing season of crops. Therefore, effective preservation, such as the ensiling of local forage, is becoming increasingly important to balance the seasonal imbalance between the forage supply and the nutritional needs of domestic animals in this area. However, the structure of the microbial community of the forage, which is influenced by climatic conditions such as altitude differences, has a major impact on the fermentation quality and microbial succession of the ensiled forage. Therefore, we investigated microbial community dynamics, co-occurrence, functional shifts, and natural fermentation profiles of Elymus nutans silage as a function of altitudinal gradients. Results show that silage from Chenduo at higher elevations has better fermentation quality and higher abundance of Lacticaseibacillus and Levilactobacillus than ensiled forage from other regions. This work may contribute to guiding for silage production in QTP.

Effect of isolated lactic acid bacteria on the quality and bacterial diversity of native grass silage

Objective

The objective of this study was to isolate lactic acid bacteria (LAB) from native grasses and naturally fermented silages, determine their identity, and assess their effects on silage quality and bacterial communities of the native grasses of three steppe types fermented for 60 days.

Methods

Among the 58 isolated LAB strains, Limosilactobacillus fermentum (BL1) and Latilactobacillus graminis (BL5) were identified using 16S rRNA sequences. Both strains showed normal growth at 15- 45°C temperature, 3-6.5% NaCl concentration, and pH 4-9. Two isolated LAB strains (labeled L1 and L5) and two commercial additives (Lactiplantibacillus plantarum and Lentilactobacillus buchneri; designated as LP and LB, respectively) were added individually to native grasses of three steppe types (meadow steppe, MS; typical steppe, TS; desert steppe, DS), and measured after 60 d of fermentation. The fresh material (FM) of different steppe types was treated with LAB (1 × 10⁵ colony forming units/g fresh weight) or distilled water (control treatment [CK]).

Results

Compared with CK, the LAB treatment showed favorable effects on all three steppe types, i.e., reduced pH and increased water-soluble carbohydrate content, by modulating the microbiota. The lowest pH was found in the L5 treatment of three steppe types, at the same time, the markedly (p < 0.05) elevated acetic acid (AA) concentration was detected in the L1 and LB treatment. The composition of bacterial community in native grass silage shifted from Pantoea agglomerans and Rosenbergiella nectarea to Lentilactobacillus buchneri at the species level. The abundance of Lentilactobacillus buchneri and Lactiplantibacillus plantarum increased significantly in L1, L5, LP, and LB treatments, respectively, compared with CK (p < 0.05).

Conclusion

In summary, the addition of LAB led to the shifted of microbiota and modified the quality of silage, and L. fermentum and L. graminis improved the performance of native grass silage.

Community Synergy of Lactic Acid Bacteria and Cleaner Fermentation of Oat Silage Prepared with a Multispecies Microbial Inoculant

To investigate community synergy of lactic acid bacteria (LAB) and cleaner fermentation of oat silage, oat silages were prepared with or without (control) commercial LAB inoculants LI1 (containing Lactiplantibacillus plantarum, Lentilactobacillus buchneri, Lacticaseibacillus paracasei, and Pediococcus acidilactici) and LI2 (containing Lactiplantibacillus plantarum and Lentilactobacillus buchneri). The microbial community, LAB synergy, and cleaner fermentation were analyzed at 1, 3, 6, 15, 35, and 90 days of ensiling. The LAB inoculant improved fermentation quality, with significantly (P < 0.05) lower pH, ammonia nitrogen content, and gas production and higher lactic acid and acetic acid contents than those of the control. Enterobacteriaceae was the main bacterial community in early stage of fermentation, which utilizes sugar to produce CO2 gas, causing dry matter (DM) and energy loss. As fermentation progressed, the microbial diversity decreased, and the microbial community shifted from Gram-negative to Gram-positive bacteria. The inoculation of multispecies LAB displayed community synergy; Pediococcus acidilactici formed a dominant community in the early stage of fermentation, which produced an acid and anaerobic environment for the subsequent growth of Lentilactobacillus and Lacticaseibacillus species, thus forming a LAB-dominated microbial community. The predicted functional profile indicated that the silage inoculated with LI1 enhanced the carbohydrate metabolism pathway but inhibited the amino acid metabolism pathway, which played a role in promoting faster lactic acid production, reducing the decomposition of protein to ammonia nitrogen, and improving the fermentation quality of silage. Therefore, oat silage can be processed to high-quality and cleaner fermented feed by using an LAB inoculant, and LI1 showed better efficiency than LI2. IMPORTANCE Oat natural silage is rich in Enterobacteriaceae, increasing gas production and fermentation loss. Lactic acid bacteria interact synergistically to form a dominant community during ensiling. Pediococci grow vigorously in the early stage of fermentation and create an anaerobic environment. Lactobacilli inhibit the harmful microorganisms and result in cleaner fermentation of oat silage.

Dry matter content and inoculant alter the metabolome and bacterial community of alfalfa ensiled at high temperature

Alfalfa silage fermentation quality, metabolome, bacterial interactions, and successions as well as their predicted metabolic pathways were explored under different dry matter contents (DM) and lactic acid bacteria (LAB) inoculations. Silages were prepared from alfalfa with DM contents of 304 (LDM) and 433 (HDM) g/kg fresh weight and inoculated with Lactiplantibacillus plantarum (L. plantarum, LP), Pediococcus pentosaceus (P. pentosaceus, PP), or sterile water (control). The silages were stored at a simulated hot climate condition (35°C) and sampled at 0, 7, 14, 30, and 60 days of fermentation. The results revealed that HDM significantly improved the alfalfa silage quality and altered microbial community composition. The GC-TOF-MS analysis discovered 200 metabolites in both LDM and HDM alfalfa silage, mainly consisting of amino acids, carbohydrates, fatty acids, and alcohols. Compared with LP and control, PP-inoculated silages had increased concentrations of lactic acid (P < 0.05) and essential amino acids (threonine and tryptophan) as well as decreased pH, putrescine content, and amino acid metabolism. However, alfalfa silage inoculated with LP had higher proteolytic activities than control and PP-inoculated silage, as revealed by a higher concentration of ammonia nitrogen (NH₃-N), and also upregulated amino acid and energy metabolism. HDM content and P. pentosaceus inoculation significantly altered the composition of alfalfa silage microbiota from 7 to 60 days of ensiling. Conclusively, these results indicated that inoculation with PP exhibited great potential in enhancing the fermentation of silage with LDM and HDM via altering the microbiome and metabolome of the ensiled alfalfa, which could help in understanding and improving the ensiling practices under hot climate conditions. KEY POINTS: • HDM improved fermentation quality and declined putrescine content of alfalfa silage • P. pentosaceus inoculation enhanced the fermentation quality of alfalfa silage • P. pentosaceus is an ideal inoculant for alfalfa silage under high temperature.

Effects of Lactic Acid Bacteria Reducing the Content of Harmful Fungi and Mycotoxins on the Quality of Mixed Fermented Feed

The contamination of fermented feeds and foods with fungi and mycotoxins is a major food safety issue worldwide. Certain lactic acid bacteria (LAB), generally recognized as safe (GRAS) fermentation probiotics, are able to reduce microbial and mycotoxins contamination. In this study, Lactiplantibacillus (L.) plantarum Q1-2 and L. salivarius Q27-2 with antifungal properties were screened as inoculants for mixed fermenting feed, and the fermentation and nutritional qualities, microbial community, and mycotoxins of mixed fermented feed were analyzed at different fermentation periods (1, 3, 7, 15, and 30 days, respectively). The findings indicated that the utilization of Q1-2 and Q27-2 strains in fermenting feed led to a decrease in pH and an increase in lactic acid concentration and the proportion of Lactiplantibacillus, while effectively restraining the proliferation of undesirable microorganisms. In particular, Q1-2 reduced the relative abundance of fungi including Fusarium and Aspergillus. Compared to the control group, the Q1-2 and Q27-2 groups reduced aflatoxin B1 by 34.17% and 16.57%, and deoxynivalenol by up to 90.61% and 51.03%. In short, these two LAB inoculants could reduce the contents of aflatoxin B1 and deoxynivalenol to the limited content levels stipulated by the Chinese National Standard GB 13078-2017. These findings suggest that the LAB strains of Q1-2 and Q27-2 have potential applications in the feed industry for the mitigation of mycotoxin pollution, thereby enhancing the quality of animal feed.

Diurnal Variation of Epiphytic Microbiota: an Unignorable Factor Affecting the Anaerobic Fermentation Characteristics of Sorghum-Sudangrass Hybrid Silage

Forage epiphytic microbiota exhibits pronounced changes in composition and function throughout the day. However, the effects of these changes on silage fermentation are rarely explored. Here, we transplanted the epiphytic microbiota of sorghum-sudangrass hybrid (SSG) harvested at 7:00 h (AM), 12:00 h (M), and 17:00 h (PM) to sterilized SSG to evaluate the effects of diurnal variation of epiphytic microbiota on fermentation characteristics. During fermentation, remarkable differences in bacterial community successions were observed between silages inoculated with AM and M microbiota. Compared to AM microbiota, M microbiota inoculation increased the proportions of Pantoea dispersa, Leuconostoc lactis, Enterobacter, and Klebsiella variicola, whereas it decreased the proportions of Weissella cibaria and Lactobacillus plantarum during fermentation. This led to the most rapid pH declines and organic acid production in AM silage and the slowest in M silage. Both M and PM microbiota affected the bacterial cooccurrence patterns, indicated by decreased complexity and stability in the community structures of M and PM silages compared to that of AM silage. The predicted functions indicated that some key carbohydrate metabolism pathways related to lactic acid synthesis were downregulated, while some competing pathways (ascorbate and aldarate metabolism and C5-branched dibasic acid metabolism) were upregulated in M silage compared to AM silage after 3 days of fermentation. Correlation analysis revealed positive correlations between competing pathways and enterobacterial species. The current study highlights the importance of diurnal variation of epiphytic microbiota in affecting the silage bacterial community, potentially providing an effective strategy to improve silage quality by optimizing harvest time. IMPORTANCE Ensiling is a way to preserve wet biomass for animal and bioenergy production worldwide. The fermentation quality of silage is largely dependent on the epiphytic microbiota of the material. Plant epiphytic microbiota exhibit diurnal changes in composition and function. However, the effects of these changes on silage fermentation are rarely explored. The results presented here demonstrated that diurnal variation of epiphytic microbiota could affect the fermentation characteristics and bacterial community during SSG fermentation. Marked bacterial community differences were observed between AM and M silages during the initial 3 days of fermentation. The dominance rate of Lactobacillus plantarum was highest in AM silage, whereas enterobacterial species were more abundant in M silage. The predicted function revealed downregulated lactic acid synthesis pathways and upregulated competing pathways in M silage compared to those in AM silage. This study provides clues for technological-parameter optimization of the fermentation process by the selection of harvest time.

Lactobacillus plantarum and propionic acid improve the fermentation quality of high-moisture amaranth silage by altering the microbial community composition

Objective

The objective of this study was to determine the effect of Lactobacillus plantarum (L. plantarum) and propionic acid (PA) on the microbial community and fermentation performance of high-moisture amaranth silage.

Methods

Amaranth silages were rown without addition (AhGCK) as a control and with L. plantarum JYLP-002 (AhGLP) or propionic acid (AhGPA) and then were opened after 60 days of ensiling to determine the microbial community and fermentation quality.

Results

Crude protein (CP) content, lactic acid (LA) content, and lactic acid bacteria (LAB) counts were significantly higher in AhGLP and AhGPA compared with those in AhGCK (p < 0.05). In contrast, pH, acetic acid (AA) content, and yeast and aerobic bacteria counts were significantly lower in AhGLP and AhGPA compared with those in AhGCK (p < 0.05). In addition, propionic acid (PA) levels were markedly higher in AhGPA (p < 0.05). In terms of microbial communities, the silage in the additive groups showed an increased relative abundance of Lactiplantibacillus plantarum and Lentilactobacillus buchneri and a reduced relative abundance of Enterobacter cloacae and Clostridium tyrobutyricum. The abundance of Xanthomonas oryzae was significantly increased in AhGPA, but completely inhibited in the silage supplemented with L. plantarum. Spearman's correlation analysis revealed that Lentilactobacillus buchneri and Levilactobacillus brevis were positively associated with LA and negatively associated with pH. Conversely, Clostridium tyrobutyricum and Enterobacter cloacae were negatively associated with LA, but positively associated with pH and AA content. AA content was inversely correlated with Lentilactobacillus buchneri. Functional prediction analysis showed that LAB dominated the three groups of silage and the silages containing additives had improved carbohydrate and amino acid metabolism compared with the control silage; in particular, the AhGLP group had more heterotypic fermentation processes and a richer metabolic pathway. Furthermore, the epiphytic Lactiplantibacillus plantarum and Lentilactobacillus buchneri could inhibit the reproductive activity of undesirable microorganisms to a certain extent, thus slowing the spoilage process of the silage.

Conclusion

In conclusion, L. plantarum can improve fermentation characteristics by modulating the microbial community attached to high-moisture amaranth silage and will prove useful for preserving high-moisture silage.

Effects of Isolated LAB on Chemical Composition, Fermentation Quality and Bacterial Community of Stipa grandis Silage

This study aimed to screen and identify lactic acid bacteria (LAB) strains from the Stipa grandis and naturally fermented silage, and assess their effects on the silage quality and bacterial community of Stipa grandis after 60 days of the fermentation process. A total of 38 LAB were isolated, and strains ZX301 and YX34 were identified as Lactiplantibacillus plantarum and Pediococcus pentosaceus using 16S rRNA sequences; they can normally grow at 10−30 °C, with a tolerance of pH and NaCl from 3.5 to 8.0 and 3 to 6.5%, respectively. Subsequently, the two isolated LAB and one commercial additive (Lactiplantibacillus plantarum) were added to Stipa grandis for ensiling for 60 days and recorded as the ZX301, YX34, and P treatments. The addition of LAB was added at 1 × 105 colony-forming unit/g of fresh weight, and the same amount of distilled water was sprayed to serve as a control treatment (CK). Compared to the CK treatment, the ZX301 and YX34 treatments exhibited a positive effect on pH reduction. The water-soluble carbohydrate content was significantly (p < 0.05) increased in ZX301, YX34, and P treatments than in CK treatment. At the genus level, the bacterial community in Stipa grandis silage involves a shift from Pantoea to Lactiplantibacillus. Compared to the CK treatment, the ZX301, YX34, and P treatments significantly (p < 0.05) increase the abundance of Pediococcus and Lactiplantibacillus, respectively. Consequently, the results indicated that the addition of LAB reconstructed microbiota and influenced silage quality. The strain ZX301 could improve the ensiling performance in Stipa grandis silage.

Effect of lactobacilli inoculation on protein and carbohydrate fractions, ensiling characteristics and bacterial community of alfalfa silage

Introduction

Alfalfa (Medicago sativa L.) silage is one of the major forages with high protein for ruminants.

Methods

The objective of this study was to investigate the effects of lactobacilli inoculants on protein and carbohydrate fractions, ensiling characteristics and bacterial community of alfalfa silage. Wilted alfalfa (35% dry matter) was inoculated without (control) or with Lactobacillus coryniformis, Lactobacillus casei, Lactobacillus plantarum, and Lactobacillus pentosus and ensiled for 7, 15, and 60 days.

Results and discussion

Silage inoculated with L. pentosus was superior to L. coryniformis, L. casei, L. plantarum in improving the fermentation quality of alfalfa silage, as indicated by the lowest ammonia nitrogen content and silage pH during ensiling. There was minor difference in water soluble carbohydrates content among all silages, but L. pentosus inoculants was more efficient at using xylose to produce lactic acid, with lower xylose content and higher lactic acid content than the other inoculants. Compared with the control, L. pentosus inoculants did not affect true protein content of silage, but increased the proportions of buffer soluble protein and acid detergent soluble protein. The L. pentosus inoculants reduced the bacterial diversity In alfalfa silage with lower Shannon, Chao1, and Ace indices, and promoted relative abundance of lactobacillus and decreased the relative abundance of Pediococcus compared with the control. As well as L. pentosus inoculants up-regulated amino acid, carbohydrate, energy, terpenoids, and polypeptides metabolism, and promoted lactic acid fermentation process. In summary, the fermentation quality and nutrient preservation of alfalfa silage were efficiently improved by inoculated with L. pentosus.

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.

The Chemical Composition, Fermentation End-Product of Silage, and Aerobic Stability of Cassava Pulp Fermented with Lactobacillus casei TH14 and Additives

This study evaluated the effects of cassava pulp fermented with Lactobacillus casei TH14, urea, and molasses on its chemical composition, the fermentation end-product of silage, and aerobic stability. A 2 × 2 × 2 factorial arrangement with a randomized complete block design was employed. The first factor: level of L. casei TH14 [L; 0 and 105 cfu/kg fresh matter (FM)], the second factor: level of molasses (M; 0 and 4% DM), the third factor: level of urea (U; 0 and 4% DM), and the number of days of fermentation (7, 14, and 21 days) were evaluated using a statistical block. There were interactions among CSP fermented with different additives on DM content (p < 0.05). The control group (CON) and CSP fermented with L, L×M, and L×U had lower DM contents than U, U×M, and L×U×M. The crude protein of CSP was increased by interaction of L×U and U×M additives (p < 0.05 and p < 0.01, respectively). Interaction effects between L and U and NDF content were detected (p < 0.05). The L×U combination resulted in a significantly lower NDF than the other groups. The interaction between L×U×M had no effect on the change in the CSP fermentation process (p > 0.05). The combination of U×M caused a poorer pH than other groups (p < 0.01). The ammonia-N content was higher than others, when CSP was fermented with L×U (p < 0.01) or U×M (p < 0.05), respectively. The lactic acid levels in fermented CSP were higher (p < 0.01) than in other groups through the L. casei. The interaction between L×U×M had an influence on lactic acid bacteria (LAB) (p < 0.01) and aerobic bacteria (p < 0.01). The highest LAB population (p < 0.01) at 106 cfu/g FM was found in CSP fermented with L. casei and molasses. In conclusion, the current study shows that CSP treated with L×U×M resulted in good preservation by recovering DM, a low number of aerobic bacteria, and greater LAB than other treatments, with the exception of the L×U×M addition. A 21-day fermentation period is advised because it produces products with greater levels of crude protein, lactic acid, acetic acid, and propionic acid.

Substitution of raw lucerne with raw citrus lemon by-product in silage: In vitro apparent digestibility and gas production

Fruit pomace addition to lucerne silage could rapidly reduce silage pH creating an acidic environment and thus maybe preventing spoilage. However, the purpose of this study was to investigate the effect of different rates of inclusion of citrus lemon by-products on lucerne. In this study, the following five different treatments were prepared: L0 (control) with 100% lucerne; L25 (75% lucerne with 25% lemon pomace); L50 (50% lucerne with 50% lemon pomace); L75 (25% lucerne with 75% lemon pomace); and L100 (100% lemon pomace). After ensiling, the chemical composition, nutritive value, stability, in vitro apparent digestibility, and gas production of silage were determined. The dry matter (DM) content was higher for lemon pomace substitution equal to or exceeded 50% (P &lt; 0.01). Crude protein, on the contrary, decreased (P &lt; 0.01) over the same percentage of substitution. The L100 and L75 treatments showed higher DM apparent disappearance rate and lower (P &lt; 0.05) crude protein and neutral detergent fiber apparent degradation rate vs. L0. Lemon pomace could be used at high inclusion level in lucerne silage, allowing the preservation of this by-product all the year, improving some chemical silage characteristics, and reducing proteolytic processes that usually happen on lucerne silage. Moreover, the in vitro apparent digestibility and gas production results showed that a partial substitution of lucerne with lemon pomace is able to improve silage digestibility.

Evaluating the fermentation characteristics, bacterial community, and predicted functional profiles of native grass ensiled with different additives

Bioaugmentation of native grass ensiling with Lactobacillus plantarum or Lactobacillus buchneri or Pediococcus pentosaceus on the ensiling performance and bacterial community was investigated after 30 days of the fermentation process. The native grass was inoculated with distilled water, Lactobacillus plantarum, Lactobacillus plantarum, and Lactobacillus buchneri, and Lactobacillus plantarum, Lactobacillus buchneri, and Pediococcus pentosaceus as the CON treatment, T1 treatment, T2 treatment, and T3 treatment, respectively. The addition of lactic acid bacteria was added at a total of 1 × 10⁶ colony-forming unit/g of fresh weight. As expected, the markedly (p < 0.05) lower water-soluble carbohydrate content was tested in the T2 and T3 treatments compared to the CON and T1 treatments. Compared to the CON and T1 treatment, significantly (p < 0.05) higher crude protein content, and lower acid detergent fiber and neutral detergent fiber contents were found in the T2 and T3 treatments. Compared to the CON treatment, the pH significantly (p < 0.05) decreased in the lactic acid bacteria (LAB) inoculated silage, and the lowest pH was measured in the T3 treatment. Similarly, significantly higher lactic acid and acetic acid contents were also found in the T3 treatment compared to those in other treatments. After 30 days of ensiling, the Shannon and Chao1 indexes in silages decreased compared to that in the fresh materials (FMs). The principal coordinate analysis indicated that both FM and silage were distinctly separated in each treatment with no interactions on the confidence ellipse (R = 0.8933, p = 0.001). At the phylum level, the dominant phylum was shifted from Proteobacteria to Firmicutes after the fermentation process. Interestingly, Weissella dominated the fermentation in the CON treatment and Lactobacillus dominated the fermentation in all inoculated LAB silages at the genus level. Results of functional prediction analyses showed that the metabolism of amino acid, cofactors, and vitamins, and membrane transport was reduced, while the metabolism of nucleotide and majority carbohydrates was increased after ensiling. The complex LAB (Lactobacillus plantarum, Lactobacillus buchneri, and Pediococcus pentosaceus) exhibited the potential possibility to decrease pH and enhance the relative abundance of LAB in response to obtaining high-quality silage by the synergistic effects. These results suggested that the complex LAB could improve the ensiling performance of native grass silage, and lay a theoretical basis for inoculant application in native grass.

Changes to the microbiome of alfalfa during the growing season and after ensiling with Lentilactobacillus buchneri and Lentilactobacillus hilgardii inoculant

AIMS

This study evaluated changes in epiphytic microbial population of alfalfa (Medicago sativa) during the growing season. First cut forage was harvested to study the effects of an inoculant combining two obligate heterofermentative lactic acid bacteria strains on the bacterial and fungal communities and the fermentation of alfalfa silage.

METHODS AND RESULTS

The epiphytic microbiome of alfalfa was evaluated 10-times during the growing season. Alfalfa wilted to 395.0 g/kg was treated with water (Control) or with a combination of L. buchneri NCIMB 40788 and L. hilgardii CNCM-I-4785 (LBLH). Mini-silos were opened after 1, 4, 8, 16, 32, and 64 days of ensiling. The relative abundance (RA) of the epiphytic bacterial and fungal families varied during the growing season. After 1 day, Weissella was the most abundant genus and present at similar RA in the two treatments (average 80.4%). Compared with Control, LBLH had a higher RA of Lactobacillus at day 1, 16, 32, and 64, and a lower RA of Weissella from day 8 to 64. Control contained more bacteria belonging to the Enterobacteriales than LBLH up to day 16. Inoculated silage had more acetate than Control at day 32 and 64. The fungal population were similar between treatments. The enhanced development and dominance of Lactobacillus in inoculated silage led to greater accumulation of acetate and propionate, which reduced the numbers of culturable yeasts but did not markedly affect the fungal community structure.

CONCLUSIONS

The bacterial community composition of alfalfa stands in the filed changed over time and was affected by cutting. For the ensiling trial, inoculation modified the composition of the bacterial community of alfalfa, increasing the RA of Lactobacillus while reducing the RA of Weissella and of Enterobacteriaceae.

SIGNIFICANCE AND IMPACT OF STUDY

Inoculation increased the RA of Lactobacillus, hampering the dominance of Weissella in the early stages of ensiling, improving antifungal compounds production and reducing the numbers of culturable yeasts.

Effects of Lactic Acid Bacteria Additives on the Quality, Volatile Chemicals and Microbial Community of Leymus chinensis Silage During Aerobic Exposure

Silage exposed to air is prone to deterioration and production of unpleasant volatile chemicals that can seriously affect livestock intake and health. The aim of this study was to investigate the effects of Lactobacillus plantarum (LP), Lactobacillus buchneri (LB), and a combination of LP and LB (PB) on the quality, microbial community and volatile chemicals of Leymus chinensis silage at 0, 4, and 8 days after aerobic exposure. During aerobic exposure, LP had higher WSC and LA contents but had the least aerobic stability, with more harmful microorganisms such as Penicillium and Monascus and produced more volatile chemicals such as Isospathulenol and 2-Furancarbinol. LB slowed down the rise in pH, produced more acetic acid and effectively improved aerobic stability, while the effect of these two additives combined was intermediate between that of each additive alone. Correlation analysis showed that Actinomyces, Sphingomonas, Penicillium, and Monascus were associated with aerobic deterioration, and Weissella, Pediococcus, Botryosphaeria, and Monascus were associated with volatile chemicals. In conclusion, LB preserved the quality of L. chinensis silage during aerobic exposure, while LP accelerated aerobic deterioration.

Gamma-ray irradiation and microbiota transplantation to separate the effects of chemical and microbial diurnal variations on the fermentation characteristics and bacterial community of Napier grass silage

BACKGROUND

To investigate the contributions of chemical and microbial diurnal variations in fermentation characteristics and bacterial community of Napier grass silage, gamma-ray irradiated Napier grass harvested at 07.00 h (AM), 12.00 h (M) and 17.00 h (PM) was inoculated with the microbiota derived from Napier grass harvested at AM, M and PM in a 3 (irradiated forage: AM_G , M_G and PM_G ) × 3 (microbiota: AM_M , M_M and PM_M ) design and then ensiled for 14 and 60 days.

RESULTS

Napier grass harvested at various times had different chemical compositions and epiphytic microbiota prior to ensiling. For silages inoculated with the same microbiota, the pH values, residual water soluble carbohydrates and dry matter contents increased, and lactic acid, acetic acid, propionic acid, butyric acid, ethanol and volatile fatty acids contents decreased in PM_G and M_G silages compared to AM_G silages. M_M and PM_M inoculum promoted lactic acid fermentation as indicated by higher lactic acid contents and lactic/acetic acid ratios in M_M and PM_M -inculated silages compared to those in AM_M -inoculated silages after 60 days of ensiling. During ensiling, epiphytic microbiota affected the Chao1 index, operational taxonomic units (OTUs) number and Shannon index, as well as the abundances, of more than half of the top 10 abundant genera, whereas chemical composition did not affect any of the bacterial diversity and richness indices and only showed significant impacts on the abundances of two genera.

CONCLUSION

The results indicated that chemical diurnal variation exerted an influence mainly on the extent of fermentation, whereas microbial diurnal variation affected more the bacterial community and fermentation types during Napier grass ensiling. © 2022 Society of Chemical Industry.

Effects of Cellulase, Lactobacillus plantarum, and Sucrose on Fermentation Parameters, Chemical Composition, and Bacterial Community of Hybrid Pennisetum Silage

Hybrid Pennisetum (HP) is a perennial herb with a high yield and high quality, which makes it valuable for research as feed for herbivores. In order to make better use of hybrid Pennisetum as feed, this study studied the effects of cellulase (CE), Lactobacillus plantarum (LP), sucrose (SU), and their mixtures on fermentation parameters, chemical composition, and the bacterial community of hybrid Pennisetum silage. The experiment was divided into 7 treatments, silage treatment, and its abbreviation: CON (control group), CE (100 U/g FM cellulase), LP (1 × 106 cfu/g FM Lactobacillus plantarum), SU (1% FM sucrose), CE+LP (100 U/g FM cellulase + 1 × 106 cfu/g FM Lactobacillus plantarum), CE+SU (100 U/g FM cellulase + 1% FM sucrose), and LP+SU (1 × 106 cfu/g FM Lactobacillus plantarum + 1% FM sucrose). The silage bag was opened on the 60th day of ensilage for subsequent determination. The addition of CE and LP increased lactic acid content (p > 0.05). The pH and acetic acid of CE and LP were lower than CON (p < 0.05), and the crude protein content of CE was higher than CON. Cellulase and Lactobacillus plantarum can improve the quality of hybrid Pennisetum silage. Compared with Lactobacillus plantarum and sucrose, cellulase has better nutrition preservation and the ability to inhibit protein hydrolysis. 16S rRNA analysis showed that the dominant phyla were Fimicutes and Proteobacteria, and the dominant genera were Lactobacillus and Weissella. The changes in fermentation parameters and chemical components of hybrid Pennisetum silage caused by cellulase, Lactobacillus plantarum, sucrose, and their mixture may be the result of bacterial community changes.

The effects of lactic acid bacteria and molasses on microbial community and fermentation performance of mixed silage of king grass and cassava foliage

In the present study, we aim to investigate the effects of lactic acid bacteria (LAB) and molasses (M) on the microbial community and fermentation performance of mixed silage of king grass (KG) and cassava foliage (CF). A completely randomized design was used for the experiment. Mixed material was ensiled with no additive added (CK) for 60 days. Alternatively, mixed silage was supplemented with M, LAB (L), or M + LAB (ML) and then subjected to fermentation. Compared with the CK group, the contents of lactic acid and propionic acid in the L group were enhanced, whereas the content of acetic acid was reduced. Moreover, the levels of pH, butyric acid, and ammonia-N were not significantly changed. In contrast, the lower contents of pH, acetic acid, propionic acid, and butyric acid, as well as ammonia-N in the M and ML groups were observed, whereas the content of lactic acid was elevated. Additives could change the silage quality of mixed silage to different extents. The effect of the L treatment was not ideal, and the ML group had a better fermentation quality compared with the M group. In terms of microbial community, the relative abundance of desirable Lactobacillus was increased in the M, L, and ML groups. The relative abundance of Pseudomonas was decreased in the M and L groups. Compared with the CK group, the relative abundance of Stenotrophomonas was decreased, especially in the M (0.18%) and ML (0.19%) groups. For Paenibacillus, its relative abundance was increased in the ML group and more significantly increased in the M group. In summary, the combination of LAB and M at an equal ratio had a more positive effect on the fermentation quality and microbial community of mixed silage than LAB and M alone.

An innovative strategy to enhance the ensiling quality and methane production of excessively wilted wheat straw: Using acetic acid or hetero-fermentative lactic acid bacterial community as additives

Ensiling is an effective storage strategy for agricultural biomass, especially for energy crops (mainly energy grasses and maize). However, the ensiling of excessively wilted crop straw is limited due to material characteristics, such as a high lignocellulosic content and low water-soluble carbohydrate and moisture contents. In this study, acetic acid or hetero-fermentative lactic acid bacterial community (hetero-fermentative LAB) were employed as silage additives to improve the ensiling process of excessively wilted wheat straw (EWS). The results showed that the additives inhibited the growth of Enterobacteriaceae and Clostridium_sensu_stricto_12, whose abundances decreased from 55.8% to 0.03-0.2%, respectively. The growth of Lactobacillus was accelerated, and the abundances increased from 1.3% to 80.1-98.4% during the ensiling process. Lactic acid fermentation was the dominant metabolic pathway in the no additive treatment. The additives increased acetic acid fermentation and preserved the hemicellulose and cellulose contents, increasing the methane yield by 17.7-23.9%. This study shows that ensiling with acetic acid or hetero-fermentative LAB is an effective preservation and storage strategy for efficient methane production from EWS.

Microbial Community, Fermentation Quality, and in vitro Degradability of Ensiling Caragana With Lactic Acid Bacteria and Rice Bran

This study aimed to assess the effects of microbial inoculants and growth stage on fermentation quality, microbial community, and in vitro degradability of Caragana silage from different varieties. Caragana intermedia (CI) and Caragana korshinskii (CK) harvested at the budding (BU) and blooming (BL) stages were used as raw materials to prepare silage, respectively. The silages at each growth stage were treated for ensiling alone (control), with 5% rice bran (RB), a combination of RB with commercial Lactobacillus plantarum (RB + LP), and a combination of RB with a selected strain Lactobacillus plantarum L694 (RB + L694). The results showed that the crude protein (CP) content of CI was higher than that of CK, and delay in harvest resulted in greater CP content in Caragana at BL stage. After 60 days of fermentation, the concentrations of lactic acid (LA) in the RB + L694 treatments were higher than those in control treatments (p < 0.05), while the pH, concentrations of NH3-N, neutral detergent fiber with the addition of α-amylase (aNDF) were lower than those in control treatments (p < 0.05). RB + L694 treatments could decrease acid detergent fiber (ADF) content except in CIBL. In CK silages, adding RB + L694 could reduce bacterial diversity and richness (p < 0.05). Compared with the control, RB + L694 treatment contained higher Lactobacillus and Enterobacter (p < 0.05). In vitro NDF and DM degradability (IVNDFD and IVDMD) was mostly affected by growth period, and additive RB + l694 treatment had higher IVDMD and lower IVNDFD than other treatments (p < 0.05). Consequently, the varieties, growth stages, and additives could influence the fermentation process, while the blooming stage should be selected in both Caragana. Furthermore, the results showed that RB and L. plantarum could exert a positive effect on fermentation quality of Caragana silage by shifting bacterial community composition, and RB + L694 treatments outperformed other additives.

Effects of fatty acid salts on fermentation characteristics, bacterial diversity and aerobic stability of mixed silage prepared with alfalfa, rice straw and wheat bran

BACKGROUND

The objective was to determine effects of potassium diformate (PD), sodium diacetate (SD) and calcium propionate (CAP) on dynamics of microbial community, fermentation characteristics and aerobic stability of silage comprised of a mixture of alfalfa (AF), rice straw (RS) and wheat bran (MF). Treatments included control (C), PD [5.5 g kg^-1 fresh weight (FW)], SD (7 g kg^-1 FW), and CAP (10 g kg^-1 FW), which were ensiled for 1, 3, 5, 7, 15, 30 and 45 days in vacuum-sealed polythene bags.

RESULTS

After day 1 of ensiling, the most dominant bacterial species in all silages was Weissella cibaria, whereas Lactobacillus parabrevis, L. nodensis, L. plantarum and L. paralimentarius were dominant species after 5 and 15 days of ensiling, and ultimately Pseudomonas putida and Stenotrophomonas maltophilia became dominant after 45 days. The positive correlation between PD and L. plantarum supported the lowest pH, butyric acid, ammonia nitrogen, neutral and acid detergent fiber, and hemicellulose content, and high water-soluble carbohydrates and crude protein content in PD silage. In addition, SD and CAP enriched the abundance of L. parabrevis and mainly increased lactic acid (LA) and acetic acid (AA). CAP increased abundance of L. acetotolerans after 45 days of ensiling with more LA and AA than other treatments.

CONCLUSIONS

The succession of the bacterial community of mixed silage was modulated by the three fatty acid salts; furthermore, PD and CAP further improved fermentation quality by accelerating the decrease in pH and the increase in LA. The chemical additives prolonged the aerobic stability more than 16 days. © 2021 Society of Chemical Industry.

Effects of Lactic Acid Bacterial Inoculants on Fermentation Quality, Bacterial Community, and Mycotoxins of Alfalfa Silage under Vacuum or Nonvacuum Treatment

To investigate the effects of lactic acid bacterial (LAB) inoculants and vacuuming on the fermentation quality and bacterial community, alfalfas were ensiled with or without a commercial LAB YX or Lactobacillus plantarum strain ZZUA493 for 10, 30, 60, and 90 days while undergoing either vacuum (V) or nonvacuum (NV) treatment. At 90 days, analysis of the microbial community by high-throughput sequencing was performed, and contents of aflatoxin B1 and deoxynivalenol (DON) mycotoxins in alfalfa silage were determined. In all inoculated alfalfa silage, irrespective of V or NV treatment, lactic acid (LA) content increased, pH (p < 0.05), and ammonia nitrogen (p < 0.05) content decreased, and no butyric acid was detected. Lactobacillus or Pediococcus became the dominant genus, and the abundance of Garciella decreased in alfalfa silage with the addition of either inoculant. The LAB inoculants YX and ZZUA493 helped reduce the mycotoxin content in alfalfa silage. The abundance of Garciella in the control and DON content in all alfalfa silage groups were higher (p < 0.05) in NV than V. In summary, LAB inoculants and vacuuming had a positive influence on alfalfa silage quality, and LAB inoculants were effective in reducing mycotoxins in silage alfalfa.

Effect of Different Regions and Ensiling Periods on Fermentation Quality and the Bacterial Community of Whole-Plant Maize Silage

This study aimed to explore the changes in the microbial community on the silage material surface and during the ensiling process of whole-plant maize in different regions. Whole-plant maize silages were sampled in Ziyun, Guanling, and Weinning counties within warm and humid climate areas in southern China. Silages were sampled at 0, 2, 5, 10, 20, and 45 days during ensiling. The nutritional components, fermentation properties, and microbiomes were examined to evaluate the influence of sampling area and fermentation time on the quality of silage. The results showed that the pH values of all silages significantly decreased (<4.2 at ensiling day 2) during fermentation and all silages achieved satisfactory fermentation at 45 days. Butyric acid was not detected during ensiling, and the contents of acetic acid and ammonia nitrogen in the final silages were below 6 g/kg DM and 50 g/kg total nitrogen, respectively. Weissella was the dominant epiphytic bacteria of raw material in Ziyun and Weinning, while Lactobacillus was prevalent in Guanling. Lactobacillus dominated the ensiling process, and its abundance significantly increased with increasing fermentation time in the three groups. Lactobacillus was negatively correlated with pH of all silages (p < 0.05) and positively correlated with lactic acid, propionic acid and acetic acid (p < 0.05). Furthermore, the bacterial community was significantly correlated with environmental factors. Altitude had a highly positive correlation with the abundance of Stenotrophomonas, Chryseobacterium, and Massilia (p < 0.01), while precipitation was negatively correlated with these bacteria. The humidity and average temperature significantly influenced the Lactobacillus and Weissella abundances of fresh whole-plant maize. During the ensiling process, the silages from three regions had similar bacterial dynamic changes, and the Lactobacillus formed and maintained good fermentation characteristics in whole-plant maize silage.

Two novel screened microbial consortia and their application in combination with Lactobacillus plantarum for improving fermentation quality of high-moisture alfalfa

AIMS

To enrich lignocellulolytic microbial consortia and evaluate whether a combination of these consortia and Lactobacillus plantarum can facilitate degradation of structural carbohydrates and improve fermentation quality of high-moisture alfalfa silage.

METHODS AND RESULTS

Two novel microbial consortia (CL and YL) with high lignocellulolytic potential were enriched, and had higher enzyme activities at slightly acidic conditions (pH 3.5-6.5). Two consortia were inoculated with and without combined L. plantarum (LP) to alfalfa for up to 120 days of ensiling. The two consortia alone or combined with LP significantly (p < 0.05) increased lactic-to-acetic acid ratios and decreased contents of volatile organic acids and NH₃ -N as compared to the control. Treatments that combining microbial consortia and LP further resulted in the higher contents of lactic acid (LA), water soluble carbohydrates (WSC) and crude protein, dry matter (DM) recovery, and lower neutral detergent fibre, acid detergent lignin and cellulose contents, with YLP silage showing the lowest pH (4.41) and highest LA content (76.72 g kg^-1  DM) and the conversion of WSC into LA (184.03%).

CONCLUSIONS

The addition of lignocellulolytic microbial consortia (CL or YL) to alfalfa silages as attractive silage inoculants could improve fermentation quality, and that their combination with L. plantarum appeared more effective on the degradation of structural carbohydrates and conversion of soluble carbohydrates into LA.

SIGNIFICANCE AND IMPACT OF THE STUDY

High-moisture alfalfa is difficult to ensile due to its high buffering capacity and low readily fermentable carbohydrate contents. Microbial consortia (CL and YL) can encode a broad selection of multi-functional CAZymes, and their combination with LP could be promising for the degradation of structural carbohydrates simultaneously with improvement fermentation quality, with high performance in LA production.

Characterization and identification of a novel microbial consortium M2 and its effect on fermentation quality and enzymatic hydrolysis of sterile rice straw

AIMS

To isolate and enrich lignocellulolytic microbial consortia from yak (Bos grunniens) rumen and evaluate their effects on the fermentation characteristics and enzymatic hydrolysis in rice straw silage.

METHODS AND RESULTS

A novel microbial consortium M2 with high CMCase and xylanase activities was enriched and observed to be prone to use natural carbon sources. Its predominant genus was Enterococcus, and most carbohydrate-active enzyme (CAZyme) genes belonged to the glycosyl hydrolases class. The consortium M2 was introduced with or without combined lactic acid bacteria (XA) to rice straw silage for 60 days. Inoculating the consortium M2 notably decreased the structural carbohydrate contents and pH of rice straw silages. Treatment that combines consortium M2 and XA resulted in the highest levels of lactic acid and lignocellulose degradation. The consortium M2 alone or combined with XA significantly (p < 0.01) increased water-soluble carbohydrates (WSCs), mono- and disaccharides contents compared with the XA silage. Combined addition obviously improved the enzymatic conversion efficiency of rice straw silage with higher glucose and xylose yields (23.39 and 12.91 w/w% DM, respectively).

CONCLUSIONS

Ensiling pretreatment with the microbial consortium M2 in sterile rice straw improved fermentation characteristics. The combined application of consortium M2 with XA had synergistic effects on promoting the degradation of structural carbohydrates and enzymatic hydrolysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Rice straw is difficult to ensile because of its low WSC and high structural carbohydrate contents. The microbial consortium M2 identified herein exhibits great potential for degrading fibrous substrates, and their combination with XA provides a faster and more effective synergistic strategy for biorefinery of lignocellulosic biomass.

Effects of re-ensiling on the fermentation quality and microbial community of napier grass (Pennisetum purpureum) silage

BACKGROUND

With the rapid development of animal husbandry, the silage trade has increased in frequency. The re-ensiling of materials is often required before or after trading, resulting in the exposure of the silage to air before re-sealing. To develop a re-ensiling technique for silage, different silage exposure periods were simulated to check the possible effects on the fermentation quality and microbial community of silage.

RESULTS

Fresh and wilted napier grass (Pennisetum purpureum) were ensiled for 90 days, then exposed to air for 0, 6, 12, 24, 36 or 48 h, before being re-ensiled. As a control, grass was directly ensiled for 180 days. Wilting increased the relative abundance of Klebsiella. The relative abundance of Paenibacillus in the unwilted silage was much higher than that in the wilted silage. Re-ensiling increased the relative abundance of Lactobacillus, but decreased the relative abundances of Klebsiella, Bacillus, and Paenibacillus. In addition, Lactobacillus became the dominant bacteria in the re-ensiled fresh and wilted silages. Re-ensiling within 48 h of exposure did not affect the fermentation quality of the wilted silage, whereas that of the unwilted silage declined when exposed to air for over 24 h.

CONCLUSION

Re-ensiling wilted napier grass silage within 48 h of aerobic exposure did not cause the fermentation quality to decline. The unwilted napier grass silage contained a higher relative abundance of Paenibacillus and significantly deteriorated when re-ensiled after over 24 h of aerobic exposure. © 2021 Society of Chemical Industry.

Different lactic acid bacteria and their combinations regulated the fermentation process of ensiled alfalfa: ensiling characteristics, dynamics of bacterial community and their functional shifts

The objectives of this study were to investigate the adaptation and competition of Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecalis inoculated in alfalfa silage alone or in combination on the fermentation quality, dynamics of bacterial community, and their functional shifts using single-molecule real-time (SMRT) sequencing technology. Before ensiling, alfalfa was inoculated with L. plantarum (Lp), P. pentosaceus (Pp), E. faecalis (Ef) or their combinations (LpPp, LpEf, LpPpEf) and sampled at 1, 3, 7, 14 and 60 days. After 60-days fermentation, the Lp-, Pp- and LpPp-inoculated silages had lower pH but greater concentrations of lactic acid were observed in Pp, LpEf and LpPpEf-inoculated silages. The inoculants altered the keystone taxa and the bacterial community dynamics in different manners, where L. plantarum, Weissella cibaria and L. pentosaceus dominated the bacterial communities after 14 days-fermentation in all treatments. The silages with better fermentation quality had simplified bacterial correlation structures. Moreover, different inoculants dramatically changed the carbohydrate, amino acid, energy, nucleotide and vitamin metabolism of bacterial communities during ensiling. Results of the current study indicate that effect of different inoculants on alfalfa silage fermentation was implemented by modulating the succession of bacterial community, their interactions and metabolic pathways as well during ensiling.

Contributions of epiphytic microbiota on the fermentation characteristics and microbial composition of ensiled six whole crop corn varieties

AIMS

The present study is aimed to reveal the variations in epiphytic microbial composition among six whole crop corn (WCC) varieties and their contributions on ensiling characteristics and microbial composition of WCC silage.

METHODS AND RESULTS

Six WCC varieties (JS06, YS23, BS20, JS39, JS40 and JS26) were ensiled for 90 days. All WCC varieties were well fermented with low pH value (<4·0) and high LA (73·6-124 g kg^-1 DM, dry matter) concentration. Of six varieties, JS40 had the highest LA (124 g kg^-1 DM) concentration, which was supported by highest relative abundance of Lactobacillus. Pantoea was the most dominant epiphytic bacteria in all fresh WCC varieties; however, the secondary dominant genera among six WCC were absolutely difference. Lactobacillus became predominant genus in 90-day silages except YS23. YS23 kept the more bacterial genus from fresh to 90-day silages than other silages, meanwhile Acinetobacter and Enterobacter were the dominant bacteria in YS23 silages.

CONCLUSIONS

Among six WCC varieties, JS40 silage had the highest LA. The variations in epiphytic microbiomes among fresh WCC affected terminal microbial community of 90-day silages. There were differences in fermentation characteristics among six WCC varieties, which might be partly attributed to variations in epiphytic microbiomes among fresh WCC.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study not only enriches the research on microbial communities of plant phyllosphere but also provides theoretical basis for selecting WCC varieties and inoculants for the forage production.

Effects of Citric Acid and Lactobacillus plantarum on Silage Quality and Bacterial Diversity of King Grass Silage

To better understand the mechanism underlying the citric acid (CA)-regulated silage fermentation, we investigated the bacterial community and fermentation quality of king grass (KG) ensiled without (CK) or with Lactobacillus plantarum (L), CA and the combination of L and CA (CAL). The bacterial community was characterized by using the 16Sr DNA sequencing technology. The L and CA treatments altered the silage bacterial community of KG, showing reduced bacterial diversity, while the abundance of desirable genus Lactobacillus was increased, and the abundances of undesirable genus Dysgonomonas and Pseudomonas were decreased. The additives also significantly raised the lactic acid content, dropped the pH, and reduced the contents of acetic acid, propionic acid, and ammonia-N in ensiled KG (P < 0.01). Besides, the combination treatment was more effective on silage fermentation with the highest pH and lactic acid content, while the contents of acetic acid, propionic acid, and ammonia-N were the lowest (P < 0.01). Moreover, CAL treatment exerted a notable influence on the bacterial community, with the lowest operational taxonomic unit (OTU) number and highest abundance of Lactobacillus. Furthermore, the bacterial community was significantly correlated with fermentation characteristics. These results proved that L and CA enhanced the KG silage quality, and the combination had a beneficial synergistic effect.

Microbial community dynamics during alfalfa silage with or without clostridial fermentation

This study was conducted to examine the effects of Lactobacillus plantarum (LP) and sucrose (S) on clostridial community dynamics and correlation between clostridia and other bacteria in alfalfa silage during ensiling. Fresh alfalfa was directly ensiled without (CK) or with additives (LP, S, LP + S) for 7, 14, 28 and 56 days. Clostridial and bacterial communities were evaluated by next-generation sequencing. Severe clostridial fermentation occurred in CK, as evidenced by the high contents of butyric acid, ammonia nitrogen, and clostridia counts, whereas all additives, particularly LP + S, decreased silage pH and restrained clostridial fermentation. Clostridium perfringens and Clostridium butyricum might act as the main initiators of clostridial fermentation, with Clostridium tyrobutyricum functioning as the promoters of fermentation until the end of ensiling. Clostridium tyrobutyricum (33.5 to 98.0%) dominated the clostridial community in CK from 14 to 56 days, whereas it was below 17.7% in LP + S. Clostridium was negatively correlated with the genus Lactobacillus, but positively correlated with the genera Enterococcus, Lactococcus and Leuconostoc. Insufficient acidification promoted the vigorous growth of C. tyrobutyricum of silage in later stages, which was mainly responsible for the clostridial fermentation of alfalfa silage.