Fermentation quality and aerobic stability of mulberry silage prepared with lactic acid bacteria and propionic acid

Formic acid enhances whole-plant mulberry silage fermentation by boosting lactic acid production and inhibiting harmful bacteria

Mulberry has also been regarded as a valuable source of forage for ruminants. This study was developed to investigate the impact of four additives and combinations thereof on fermentation quality and bacterial communities associated with whole-plant mulberry silage. Control fresh material (FM) was left untreated, while other groups were treated with glucose (G, 20 g/kg FM), a mixture of Lactobacillus plantarum and L. buchneri (L, 106 CFU/g FM), formic acid (A, 5 mL/kg FM), salts including sodium benzoate and potassium sorbate (S, 1.5 g/kg FM), a combination of G and L (GL), a combination of G and A (GA), or a combination of G and S (GS), followed by ensiling for 90 days. Dry matter content in the A, S, GA, and GS groups was elevated relative to the other groups (p < 0.01). Relative to the C group, all additives and combinations thereof were associated with reductions in pH and NH3-N content (p < 0.01). The A groups exhibited the lowest pH and NH3-N content at 4.23 and 3.27 g/kg DM, respectively (p < 0.01), whereas the C groups demonstrated the highest values at 4.43 and 4.44 g/kg DM, respectively (p < 0.01). The highest levels of lactic acid were observed in the GA and A groups (70.99 and 69.14 g/kg DM, respectively; p < 0.01), followed by the GL, L, and GS groups (66.88, 64.17 and 63.68 g/kg DM, respectively), with all of these values being higher than those for the C group (53.27 g/kg DM; p < 0.01). Lactobacillus were the predominant bacteria associated with each of these samples, but the overall composition of the bacterial community was significantly impacted by different additives. For example, Lactobacillus levels were higher in the G, A, and GA groups (p < 0.01), while those of Weissella levels were raised in the L, GL, and GS groups (p < 0.01), Pediococcus levels were higher in the A and GA groups (p < 0.01), Enterococcus levels were higher in the G and S groups (p < 0.01), and Lactococcus levels were raised in the S group (p < 0.01). Relative to the C group, a reduction in the levels of undesirable Enterobacter was evident in all groups treated with additives (p < 0.01), with the greatest reductions being evident in the A, S, GA, and GS groups. The additives utilized in this study can thus improve the quality of whole-plant mulberry silage to varying extents through the modification of the associated bacterial community, with A and GA addition achieving the most efficient reductions in pH together with increases in lactic acid content and the suppression of undesirable bacterial growth.

Effect of Regulation of Whole-Plant Corn Silage Inoculated with Lactobacillus buchneri or Bacillus licheniformis Regarding the Dynamics of Bacterial and Fungal Communities on Aerobic Stability

Enhancing the aerobic stability of whole-plant corn silage is essential for producing high-quality silage. Our research assessed the effect of inoculation with Lactobacillus buchneri or Bacillus licheniformis and its modulation of the bacterial and fungal microbial community structure in an aerobic stage of whole-plant corn silage. Following treatment with a distilled sterile water control, Lactobacillus buchneri, and Bacillus licheniformis (2 × 105 cfu/g), whole-plant corn was ensiled for 60 days. Samples were taken on days 0, 3, and 7 of aerobic exposure, and the results showed that inoculation with Lactobacillus buchneri or Bacillus licheniformis improved the aerobic stability of silage when compared to the effect of the control (p < 0.05). Inoculation with Bacillus licheniformis attenuated the increase in pH value and the decrease in lactic acid in the aerobic stage (p < 0.05), reducing the filamentous fungal counts. On the other hand, inoculation with Lactobacillus buchneri or Bacillus licheniformis increased the diversity of the fungal communities (p < 0.05), complicating the correlation between bacteria or fungi, reducing the relative abundance of Acetobacter and Paenibacillus in bacterial communities, and inhibiting the tendency of Monascus to replace Issatchenkia in fungal communities, thus delaying the aerobic spoilage process. Due to the prevention of the development of aerobic spoilage microorganisms, the silage injected with Lactobacillus buchneri or Bacillus licheniformis exhibited improved aerobic stability.

Lentilactobacillus buchneri Preactivation Affects the Mitigation of Methane Emission in Corn Silage Treated with or without Urea

The aim of this study was to investigate the effect of different forms of Lentilactobacillus buchneri on the in vitro methane production, fermentation characteristics, nutritional quality, and aerobic stability of corn silage treated with or without urea. The following treatments were applied prior to ensiling: (1) no urea treatment and LB; (2) no urea treatment+freeze dried LB; (3) no urea treatment+preactivated LB; (4) with urea treatment+no LB; (5) with urea treatment+freeze dried LB; (6) with urea treatment+preactivated. LB was applied at a rate of 3 × 108 cfu/kg on a fresh basis, while urea was applied at a rate of 1% on the basis of dry matter. Data measured at different time points were analyzed according to a completely randomized design, with a 2 × 3 × 5 factorial arrangement of treatments, while the others were analyzed with a 2 × 3 factorial arrangement. Preactivated LB was more effective than freeze-dried LB in reducing silage pH, ammonia nitrogen, cell-wall components, yeast count, and carbon dioxide production, as well as increasing lactic acid and residual water-soluble carbohydrate and aerobic stability (p < 0.0001). A significant reduction in the methane ratio was observed after 24 h and 48 h incubation with preactivated forms of LB (p < 0.001). The results indicated that preactivated LB combined with urea improved fermentation characteristics, nutritional quality, and aerobic stability and reduced the methane ratio of corn silages.

Characterization of Lactic Acid-Producing Bacteria Isolated from Rumen: Growth, Acid and Bile Salt Tolerance, and Antimicrobial Function

Lactic acid bacteria are some of the dominant bacteria in the rumen, and they have a high ability for lactic acid production. The present study aimed to screen and evaluate the performance of culturable rumen bacteria from Chinese Holstein dairy cows as a potential probiotic or inoculant for silage production, in order to isolate ruminal lactic acid bacteria and evaluate their potential as probiotics. Three strains of Enterococcus avium (E. avium, EA1-3); three strains of Streptococcus lutetiensis (S. lutetiensis, SL1-3); and six strains of Streptococcus equinus (S. equinus, SE1-6) were successfully identified from the rumen fluid using modified De Man Rogosa sharp medium supplemented with 0.325% lactic acid. E. avium, S. lutetiensis and S. equinus are clustered in the phylogenetic tree. All the 12 Gram-positive strains reached the plateau growth phase in 6–10 h, with an OD600 at about 1.8. Both gas and acid accumulation reached plateaus at about 10–12 h in all strains, and S. equinus showed the strongest capacity. The highest lactic acid accumulation was detected in S. equinus broth (up to 219.77 μmol/L). The growth of all isolates was inhibited at pH 4.0, and EA2, SL1, SL2, SL3 and SE2 were tolerant to 0.1%, 0.2% and 0.3% bile salt. In addition, the supernatants of the strains had inhibitory effects on Escherichia coli and Staphylococcus aureus. Specifically, the S. equinus strains exhibited the strongest inhibition of the pathogens. In conclusion, these 12 strains had good potential as silage inoculants or probiotics for edible animals, especially S. equinus.

Utilization of Waste Date Palm Leaves Biomass Ensiled with Malic or Lactic Acids in Diets of Farafra Ewes under Tropical Conditions

The aim of the current study was to evaluate the ensiling of date palm leaves (DPL) with organic acids (lactic or malic acid) for 45 day as a feed for lactating ewes under desert conditions. Two weeks before expected parturition, 50 multiparous lactating Farafra ewes (mean ± SD: 2 ± 0.3 parity, 34 ± 1.9 kg bodyweight, 25 ± 2.4 months of age, and 555 ± 13.0 g/day of previous milk production) were equally divided into five treatments in a completely randomized design for 90 day. The ewes in the control treatment were offered a diet composed of a concentrate feed mixture and DPL at 60:40 on a dry matter (DM) basis ensiled without additive. In the other treatments, DPL (ensiled without organic acids) in the control treatment was replaced with DPL ensiled with lactic or malic acid (at 5 g/kg DM) at 50 or 100% levels. Organic acids linearly and quadratically increased (p < 0.01) DPL and total intakes and digestibilities of DM, organic matter, crude protein, and nonstructural carbohydrates without affecting fiber digestibility. Malic and lactic acid treatment also increased the concentrations of ruminal total volatile fatty acids, acetate, propionate, and ammonia-N. Additionally, malic and lactic acid-treated DPL increased serum glucose concentration and total antioxidant capacity. Without affecting daily actual milk production, treatments increased (p < 0.001) the daily production of energy-corrected milk (ECM), fat-corrected milk (FCM), milk energy output, milk contents of fats, and feed efficiency. Organic acid-treated DPL increased (p < 0.05) the proportions of total polyunsaturated fatty acids and total conjugated linoleic acids and the unsaturated to saturated fatty acid ratio in milk. It is concluded that feeding DPL ensiled with malic or lactic acid at 20 or 40% of total diet DM increased daily ECM and FCM production, nutrient utilization efficiency, and milk quality. No differences were observed between lactic and malic acid treatment of DPL during ensiling; therefore, both of them are recommended to treat DPL for silage preparation.

Effects of Microbial Inoculants on Fermentation Quality and Aerobic Stability of Paper Mulberry Silages Prepared with Molasses or Cellulase

Paper mulberry (Broussonetia papyrifera L.) is an unconventional forage with high crude protein content and is widely used in China. In order to evaluate the pattern of fermentation quality and the aerobic stability when inoculated with lactic acid bacteria, laboratory-scale silage was prepared. The experimental groups included a control group (CK), a Lactobacillus plantarum ‘LC365283’ (selected from paper mulberry silage) treatment (L1), a commercial inoculant Lactobacillus plantarum treatment (GF), a commercial inoculant Lactobacillus buchneri treatment (FR), a 3% molasses treatment (MO), a 150 U/g cellulase treatment (CE), and their combinations (MO + L1, MO + GF, MO + FR, CE + L1, CE + GF, and CE + FR). The changes in bacterial community and composition of the fermentation products were evaluated after being ensiled for 30 days and unsealed for 1, 3, 5, and 7 days. Compared with the CK, MO and CE, the silages treated with L1, MO + L1, and CE + L1 showed higher lactic acid concentrations, lower pH values, and lower ammonia nitrogen concentrations (p < 0.05). During the first 3 days of aerobic exposure, the pH values and organic acid content changed slightly in all treatments. The present study suggests that addition of L1 was better than commercial inoculum, and the paper mulberry silages could be well preserved after being unsealed for 3 days.

Effects of N Fertilization During Cultivation and Lactobacillus plantarum Inoculation at Ensiling on Chemical Composition and Bacterial Community of Mulberry Silage

As unconventional forage source, mulberry (Morus alba L.) has been cultivated to alleviate animal feed shortages. This study aimed to investigate the effects of N fertilization during cultivation and Lactobacillus plantarum inoculation at ensiling on the chemical composition and bacterial community of mulberry silage. Mulberry was separately cultivated under two N fertilization rates (N1, 390 kg/ha/year; N2, 485 kg/ha/year) in 2016-2019, harvested on 30 April (the first-cut) and 15 June (the second-cut) in 2019, and then chopped for producing small bag silage. The silage was treated without (control) or with L. plantarum (LP, a recommended application rate of 10⁵ cfu/g on fresh matter basis). After storage of 60 days in dark room at ambient temperature, silage was sampled for analysis of chemical and microbial compositions. Higher (P < 0.05) final pH value and acetic acid content and lower (P < 0.05) lactic acid content were found in silage of mulberry under N2 fertilization, resulting in more dry matter loss than that under N1 fertilization. Compared with control, inoculation of LP at ensiling increased (P < 0.05) lactic acid content and decreased (P < 0.05) final pH value, acetic acid and propionic acid contents of silage, by advancing the dominance of Lactobacillus and reducing the abundance of Enterococcus and Enterobacter. In particular, inoculation of LP at ensiling decreased (P < 0.05) dry matter loss and butyric acid content of first-cut silage. In conclusion, inoculation of LP at ensiling could reduce the undesirable effects from high N fertilization rate during cultivation on silage quality of mulberry harvested at different growing seasons.

A new Leuconostoc citreum strain discovered in the traditional sweet potato sour liquid fermentation as a novel bioflocculant for highly efficient starch production

Sour liquid fermentation is commonly used in the sedimentation process of traditional starch production, where bacteria play a critical role in starch flocculation. In this study, the dynamic changes of bacterial compositions during sweet potato sour liquid (SPSL) fermentation were profiled using the single-molecule real-time (SMRT) sequencing, unveiling that Leuconostoc citreum, Leuconostoc pseudomesenteroides, Lactococcus lactis, and Lactobacillus plantarum were the dominant microorganisms in the process, and Leuconostoc citreum exhibited a strong positive correlation with starch flocculation rate (FR). In total, 75 lactic acid bacterial (LAB) strains were isolated from the SPSL, but only 7 of them caused starch flocculation. For the first time, Leuconostoc citreum strains were reported with excellent starch-flocculating abilities (up to 55.56% FR in 20 min), which might be attributed to their ability to connect starch granules through the cell surface to form large aggregation. This study provides a comprehensive understanding of the bacterial dynamics in SPSL fermentation at the species level. A starch flocculation yield of 93.63% was achieved within 1 h by using the newly discovered Leuconostoc citreum SJ-57. The time required for total starch sedimentation was reduced from 10 h to 4 h, compared with the traditional process. These results suggest that this novel bioflocculant is more suitable for modernizing the traditional SPSL fermentation process and achieving rapid and highly efficient starch sedimentation.

Enriching the nutritive value of marigold (Tagetes erecta L) crop residues as a ruminant feed by lactic acid bacteria during ensilage

Background

Marigold (Tagetes erecta L) accounts for over half of the world’s loose flower production, and marigold crop residue (MCR) are abundantly available and should be used as a forage. In this study, MCR from the last commercial flower pickings was ensilaged with lactic acid bacteria (LAB) and the shift in their volatile organic compounds (VOCs) profiles was monitored. Samples were collected at 6 different times during ensilage (3, 6, 9, 12, 15, 30 days) to determine and quantify the VOCs changes using a solid-phase microextraction (SPME) technique and gas chromatography – mass spectrometry (GC-MS).

Results

After 30 days, the caryophyllene and piperitone, which account for 14.7 and 12.1% of total VOCs, decreased by 32.9 and 9.6% respectively, alcohols increased from 2.8 to 8.1%, and the acetic acid content increased by 560%.

Conclusion

We have confirmed LAB can degrade the content of terpenes and enhance the content of alcohols and acids in MCR, which was for the first time on terpene degradation in fodder by ensilage. These results have shed light on our understanding of how to improve fodder odor and to enhance terpene degradation by lactic acid bacteria fermentation.

Treatment of Whole-Plant Corn Silage With Lactic Acid Bacteria and Organic Acid Enhances Quality by Elevating Acid Content, Reducing pH, and Inhibiting Undesirable Microorganisms

We investigated the variation in microbial community and fermentation characteristics of whole-plant corn silage after treatment with lactic acid bacteria (LAB) and organic acids. The fresh corn forages were treated with a combination of L. acidophilus and L. plantarum (10⁶ CFU/g fresh material) or a 7:1:2 ratio of formic acid, acetic acid, and propionic acid (6 mL/g fresh material) followed by 45 or 90 days of ensiling. Silages treated with LAB showed increased lactic acid content and decreased pH after 45 days. Although treatment with LAB or organic acids decreased the common and unique operational taxonomic units, indicating a reduction in microbial diversity, the relative abundance of Lactobacillus was elevated after 45 and 90 days compared with control, which was more distinct in the organic acid groups. Moreover, we found higher levels of acetic acid and increased abundance of Acetobacter in silages treated with organic acids whereas undesirable microorganisms such as Klebsiella, Paenibacillus, and Enterobacter were reduced. In summary, the quality of corn silages was improved by LAB or organic acid treatment in which LAB more effectively enhanced lactic acid content and reduced pH while organic acid inhibited the growth of undesirable microorganisms.

Ensiling of whole-plant hybrid pennisetum with natamycin and Lactobacillus plantarum impacts on fermentation characteristics and meta-genomic microbial community at low temperature

BACKGROUND

The aim of the current research was to clarify the impacts of the ensiling of whole-plant hybrid pennisetum with natamycin and Lactobacillus plantarum on fermentation characteristics and the meta-genomic microbial community at low temperatures.

RESULTS

During the ensiling process, lactic acid (LA) and lactic acid bacteria (LAB) significantly (P < 0.05) increased and acetic acid (AA), water-soluble carbohydrate (WSC), ammonia total nitrogen (NH3-N), and yeast significantly (P < 0.05) reduced in treatments as compared to controls. Different treatments and different ensiling days led to variations in the bacterial community at family and genus levels. The family Lactobacillaceae and genera Lactobacillus and Pediococcus are dominant communities in treatment silage. The family and genus levels bacterial ecology and fermentation quality were analyzed by principal component analysis (PCA). The PCO1, and PCO2 can be explained by 10.81% and 72.14% of the whole variance regularly, similarly in PCO1 and PCO2 can be explained 24.23% and 52.06% regularly. The core bacterial micro-biome operational taxonomic unit (OTU) numbers increased in treatments, as compared to controls, on different hybrid pennisetum ensiling days.

CONCLUSIONS

The inoculation of L. plantarum alone and combined with natamycin influenced the fermentation quality and reduced undesirable microorganisms during the fermentation of hybrid pennisetum silage. Natamycin alone did not significantly enhance the concentration of organic acid but numerically enhanced in treatments group as compared to control. © 2020 Society of Chemical Industry.

Effects of additives on the fermentation quality, in vitro digestibility and aerobic stability of mulberry (Morus alba L.) leaves silage

OBJECTIVE

To explore feed resources capable of replacing regular poor-quality fodder, this study was conducted to evaluate the effects of additives on the fermentation quality, in vitro digestibility and aerobic stability of mulberry leaves silage.

METHODS

The mulberry leaves were ensiled either untreated (control) or treated with 1×106 cfu/g fresh matter Lactobacillus plantarum (L), 1% glucose (G), 3% molasses (M), a combination of 1% glucose and Lactobacillus plantarum (L+G), and a combination of 3% molasses and Lactobacillus plantarum (L+M). The fermentation quality and chemical composition were analyzed after 7, 14, 30, and 60 d, respectively. The 60-d silages were subjected to an aerobic stability test and fermented with buffered rumen fluid to measure the digestibility.

RESULTS

Inoculating lactic acid bacteria (LAB) resulted in more rapid increase in lactic acid concentrations and decline in pH of mulberry leaves silage as compared control. Higher acetic acid and lower ethanol and ammonia nitrogen concentrations (p<0.05) were observed in the LAB-inoculated silages as opposed to control during ensiling. The LAB-inoculated silages contained lower water-soluble carbohydrates compared with control during the first 14 d of ensiling, and lower neutral detergent fibre (p<0.05) concentrations as compared with non-LAB inoculated silages. Adding molasses alone increased (p<0.05) the digestibility of dry matter (DM). The aerobic stability of mulberry leaves silage was increased by LAB inoculation, whereas decreased by adding glucose or molasses.

CONCLUSION

The LAB inoculation improved fermentation quality and aerobic stability of mulberry leaves silage, while adding glucose or molasses failed to affect the fermentation and impaired the aerobic stability. Inoculating LAB alone is recommended for mulberry leaves especially when ensiled at a relatively high DM.

Effects of natamycin and Lactobacillus plantarum on the chemical composition, microbial community, and aerobic stability of Hybrid pennisetum at different temperatures

This study evaluated the effects of natamycin and Lactobacillus plantarum on the chemical composition, microbial community, and aerobic stability of Hybrid pennisetum at different temperatures. Different concentrations of natamycin (0.50 g L⁻¹, 1.00 g L⁻¹, and 1.50 mg L⁻¹) significantly (p > 0.05) reduced the growth of undesirable microorganisms. During the ensiling periods the pH, ammonia nitrogen (NH₃–N), acetic acid (AA), butyric acid (BA), aerobic bacteria (AB), and yeast were significantly (p > 0.05) reduced, while the lactic acid and lactic acid bacteria were significantly (p < 0.05) influenced in the SLP and SLNP groups as compared to the SP and SNP groups at high temperature (29–30 °C). During air exposure, water-soluble carbohydrate, ammonia nitrogen (NH₃–N), lactic acid (LA), and acetic acid (AA) were not influenced, while pH and aerobic bacteria were significantly (p < 0.05) enhanced after three days (72 hours) of air exposure, and lactic acid bacteria were significantly (p > 0.05) reduced at ambient temperature (9–10 °C). It is concluded that the addition of L. plantarum CICC 20765 alone and in combination with natamycin reduced the content of AA, pH, NH₃–N, BA, and undesirable microbial community, and enhanced the chemical composition, fermentation quality, and air exposure. Natamycin alone did not significantly enhance the organic acid profile but improved the air exposure. Furthermore, more effort is needed to evaluate the effects on silage preservation on a large scale and on animal performance.

The inoculation of L. plantarum and natamycin influenced the fermentation quality. Natamycin and L. plantarum reduced the undesirable microbial community. During ensiling process, the LA and LABs was significantly enhanced.