Dynamics of proteolysis, protease activity and bacterial community of Neolamarckia cadamba leaves silage and the effects of formic acid and Lactobacillus farciminis

Ensiling characteristics, in vitro digestibility and bacterial community structure of mulberry leaf silage with or without the addition of cellulase, protease, and starch

Objective

This study aimed to investigate the effects of cellulase, protease, and starch on the fermentation quality, in vitro digestibility, and microbial community of mulberry leaf silage after 30d of ensiling.

Methods

Mulberry leaves (376 g/kg dry matter (DM)) were ensiled with four experimental treatments: i) CON, no additives; ii) CEL, added cellulase (120 U/g fresh matter [FM]); iii) CPR, added cellulase (120 U/g FM) and protease (50 U/g FM); and iv) CPS, added cellulase (120 U/g FM), protease (50 U/g FM), and starch (2% FM).

Results

All treatments with additives improved fermentation quality, showing higher DM (353 ~ 378 vs. 341 g/kg DM), lactic acid (LA) content (51.6 ~ 64.6 vs. 40.2 g/kg DM), lactic acid bacteria (LAB) counts (7.63 ~ 7.73 vs. 7.49 log10 CFU /g of FM), along with lower pH values (4.29 ~ 4.60 vs. 5.09), and DM losses (124 ~ 130 vs. 134 g/kg DM) compared to the CON group. All the additive treated groups showed higher in vitro digestibility of DM (698 ~ 720 vs. 618 g/kg DM), in vitro digestibility of NDF (395 ~ 412 vs. 336 g/kg DM), and ADF (277 ~ 298 vs. 232 g/kg DM) than CON. Among all the groups, the CPS group exhibited the highest DM content (378 g/kg DM), LA content (64.6 g/kg DM) and LAB counts (7.73 log10 CFU /g of FM), with the lowest pH value (4.29) and DM losses (124 g/kg DM). Additionally, the additive treatments increased abundance of bacteria like Firmicutes and Enteroccocus, while reducing Proteobacteria abundance, and resulted in lower diversity and richness of the microbial community. Specifically, CPR and CPS silages showed increased Pediococcus and decreased Enterobacter compared to CON and CEL, and CPS silage had a relatively high abundance of favorable Bacteroidota. Furthermore, the CPS silage exhibited upregulated genetic functions, energy and lipid metabolism, as well as metabolism of cofactors and vitamins compared to the other groups.

Conclusion

The combined application of cellulase, protease, and starch effectively improved the fermentation quality, in vitro digestibility, and microbial community of mulberry leaf silage over the 30-day ensiling period.

The microbiota and metabolome dynamics and their interactions modulate solid-state fermentation process and enhance clean recycling of brewers' spent grain

The massive yield of brewers' spent grain (BSG) waste inevitably threaten environmental health. Here, solid-state fermentation (SSF) technology featuring multi-strain (MS) inoculation and high-throughput sequencing technology were employed to facilitate the sustainable and clean recycling of BSG waste while revealing the associated underlying microbiological and metabolic mechanisms. MS inoculation displayed a lower pH value (3.91 vs. 4.12) and neutral detergent fiber content (446.24 vs. 476.23 g/kg DM), a higher levels of lactic acid (86.64 vs. 33.07 g/kg DM), acetic acid (6.13 vs. 4.87 g/kg DM), propionic acid (2.78 vs. 2.18 g/kg DM) and crude protein (307.5 vs. 289.15 g/kg DM) than those in the control group. Moreover, MS inoculation inhibited the formation of non-protein-N and ammonia-N, and spoilage microorganism resuscitation, while enhanced substrate preservation. Microbiologically, during the SSF, the group treated with MS inoculation exhibited an increase in the relative abundance of Leuconostoc (0.58%∼6.60%), Weissella (6.22%∼15.42%), Enterococcus (3.15%∼9.08%), Bacillus (17.63%∼31.29%), Lactobacillus (12.89%∼8.29%), Pseudoalteromonas (12.87%∼16.29%), and a decrease in the relative abundance of Acinetobacter (0.79%∼0.02%) and Enterobacteriaceae (0.78%∼0.24%). Metabolically, starch and sucrose metabolism, arginine and proline metabolism, and phenylalanine metabolism significantly influenced the quality of extruded BSG fermented by MS during SSF. The examination of the correlation between the microbiota, metabolites, and fermentation parameters revealed that complex interactions between microbes and the environment factors impact metabolite production. Collectively, inoculating with MS improved fermentation quality and stability, facilitated the clean recycling of BSG, which is linked to complex interactions among microbes, the environment factors and metabolite production.

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.

Green biorefinery of shrimp shell waste for α-chitin and high-value co-products through successive fermentation by co-lactic acid bacteria and proteolytic fungus

Green biorefinery process was conducted to extract α-chitin and high-value co-products from shrimp shell waste through microbial fermentation using mature coconut water (MCW) as a sole nutrient source. Symbiotic co-lactic acid fermentation (Co-LAF) by Lactobacillus plantarum and Streptococcus thermophilus produced higher levels of lactic acid (LA) and protease activity than their mono-cultures, which led to greater demineralization (DM) and deproteinization (DP) of shrimp shell powder (SSP). After optimizing Co-LAF through Response Surface Methodology and successive fermentation by an acid-active proteolytic fungus Rhizopus oligosporus, the highest DM of 94.0 ± 0.91 % and DP of 86.7 ± 0.1 % were achieved. Based on FT-IR, XRD, and SEM analysis, the bio-extracted chitin had similar structural characteristics to commercial α-chitin but with better quality. These strategies not only contribute to environmentally-friendly and cost-effective extraction of α-chitin (303 ± 18 mg/g-SSP), but also co-produce LA (57.18 ± 0.89 g/L), acid protease (4.33 ± 0.5 U/mL), bio-calcium (277 ± 12 mg-CaSO4/g-SSP), protein hydrolysate (268 ± 5 mg/g-SSP), and pigments (28.78 ± 1.56 µg/g-SSP).

Catalytic and antioxidant activity of silver nanoparticles fabricated by Neolamarckia cadamba bark extract

Plant parts have unfathomable potential in the synthesis of nanoparticles. The current study was designed for the photosynthesis of silver nanoparticles (NC-AgNPs) using bark extract of N. cadamba. Different analytical methods were used to characterize the synthesized nanoparticles. HR-TEM analysis identifies the formation of multi-shaped NC-AgNPs like spherical, quasi-spherical, rod-shaped, trigonal, square, pentagonal, and hexagonal with a size range of 18-91 nm. The crystallize size of NC-AgNPs was found to be 27.6 nm. The catalytic effectiveness of NC-AgNPs in degrading Crystal violet (CV) dye is remarkable. Important parameters such as the effect of catalyst dose and pH were investigated. Dose-dependentantioxidant activity of NC-AgNPs was determined by using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay. Low-cost synthesis and eco-friendly reagents were the salient features that made NC-AgNPs more attractive toward catalytic and antioxidant activities.

Response of fermentation quality and microbial community of oat silage to homofermentative lactic acid bacteria inoculation

Oat (Avena sativa L.) is one of the important forage crops in the world. However, oat grown in Southwest China has higher moisture content and their preservation face significant challenges. In addition, existing commercial lactic acid bacteria (LAB) have poor fermentation effects in hot and humid regions. Consequently, the current study investigated the response of oat fermentation quality and microbial community to self-selected LAB inoculation. The treatments were: CK, sterilized water; LP694, Lactobacillus plantarum 694; LR753, Lactobacillus rhamnosus 753; and LPLR, LP694 combined with LR753, followed by 1, 3, 7, 14, and 60 days (d) of fermentation. The results showed that LAB inoculation significantly raised the lactic acid content, and decreased the level of pH value, acetic acid, and ammonia-N in oat silage. The LR753 group had a significantly higher (p < 0.05) lactic acid content (60.95 g kg-1 DM), and lower pH value (3.95) and ammonia-N content (10.1 g kg-1 DM) followed by the LPLR group. The LR753 showed lower NDF (54.60% DM) and ADF (39.73% DM) contents than other groups. The Lactobacillus was a prevalent genus in LAB-treated groups, and its relative abundance reached maximum in LP694 (69%) on day 3, while in the LR753 group (72%) on 60 days. The Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus fermentum became the dominant species in LAB-treated groups with fermentation time. The Lactobacillus genus was positively correlated with WSC (R = 0.6, p < 0.05), while negatively correlated with pH (R = -0.5, p < 0.05), and BA (R = -0.5, p < 0.01). Overall, the LR753 group had better fermentation quality and preservation of nutritional components providing theoretical support and guidance for future oat silage production in Southwest China.

Anaerobic fermentation featuring wheat bran and rice bran realizes the clean transformation of Chinese cabbage waste into livestock feed

Rapid aerobic decomposition and a high cost/benefit ratio restrain the transformation of Chinese cabbage waste into livestock feed. Herein, anaerobically co-fermenting Chinese cabbage waste with wheat bran and rice bran at different dry matter levels (250, 300, 350 g/kg fresh weight) was employed to achieve the effective and feasible clean transformation of Chinese cabbage waste, and the related microbiological mechanisms were revealed by high-throughput sequencing technology. The bran treatments caused an increase in pH value (4.75-77.25%) and free amino acid content (12.09-152.66%), but a reduction in lactic acid concentration (54.58-77.25%) and coliform bacteria counts (15.91-20.27%). In addition, the wheat bran treatment improved the levels of short-chain fatty acids, nonprotein nitrogen, water-soluble carbohydrates and antioxidant activity and reduced the ammonia nitrogen contents. In contrast, the rice bran treatment decreased the levels of acetic acid, water-soluble carbohydrates, nonprotein nitrogen, ammonia nitrogen, and antioxidant activities. Microbiologically, the bran treatments stimulated Pediococcus, Lactobacillus, Enterobacter, and Weissella but inhibited Lactococcus and Leuconostoc, which were the primary organic acid producers reflected by the redundancy analysis. In addition, Chinese cabbage waste fermented with wheat bran at 350 g/kg fresh weight or with rice bran at 300 g/kg fresh weight increased the scale and complexity of bacteriome, promoted commensalism or mutualism and upregulated the global metabolism pathways, including carbohydrate and amino acid metabolisms. Furthermore, the bran treatments resulted in an increase in bacterial communities that were facultatively anaerobic, biofilm-formed, Gram-negative, potentially pathogenic and stress-tolerant. Collectively, the bran treatments inhibited effluent formation and protein degradation and improved nutrient preservation but reduced organic acid production during the anaerobic fermentation, which is linked to the variations in the bacteriome, indicating that the constructed fermentation system should be further optimized.

Dynamic Changes in Fermentation Quality and Structure and Function of the Microbiome during Mixed Silage of Sesbania cannabina and Sweet Sorghum Grown on Saline-Alkaline Land

Protein-rich Sesbania cannabina and sugar-rich sweet sorghum [Sorghum dochna (Forssk.) Snowden] are characterized by their higher tolerance to saline-alkaline stresses and simultaneous harvests. They could be utilized for coensiling because of their nutritional advantages, which are crucial to compensate protein-rich forage in saline-alkaline regions. The current study investigated the fermentation quality, microbial community succession, and predicted microbial functions of Sesbania cannabina and sweet sorghum in mixed silage during the fermentation process. Before ensiling, the mixtures were treated with compound lactic acid bacteria (LAB) inoculants followed by 3, 7, 14, 30, and 60 days of fermentation. The results revealed that the inoculated homofermentative species Lactobacillus plantarum and Lactobacillus farciminis dominated the early phase of fermentation, and these shifted to the heterofermentative species Lactobacillus buchneri and Lactobacillus hilgardii in the later phase of fermentation. As a result, the pH of the mixed silages decreased significantly, accompanied by the growth of acid-producing microorganisms, especially L. buchneri and L. hilgardii, which actively influenced the bacterial community structure and metabolic pathways. Moreover, the contents of lactic acid, acetic acid, 1,2-propanediol, and water-soluble carbohydrates increased, while the contents of ammonia-N and fiber were decreased, with increasing ratios of sweet sorghum in the mixed silage. Overall, coensiling Sesbania cannabina with >30% sweet sorghum is feasible to attain high-quality silage, and the relay action between homofermentative and heterofermentative LAB species could enhance fermentation quality and conserve the nutrients of the mixed silage. IMPORTANCE The coensiling of Sesbania cannabina and sweet sorghum is of great practical importance in order to alleviate the protein-rich forage deficiency in saline-alkaline regions. Furthermore, understanding the microbial community's dynamic changes, interactions, and metabolic pathways during ensiling will provide the theoretical basis to effectively regulate silage fermentation. Here, we established that coensiling Sesbania cannabina with >30% sweet sorghum was effective at ensuring better fermentation quality and preservation of nutrients. Moreover, the different fermentation types of LAB strains played a relay role during the fermentation process. The homofermentative species L. plantarum and L. farciminis dominated in the early phase of fermentation, while the heterofermentative species L. buchneri and L. hilgardii dominated in the later phase of fermentation. Their relay action in Sesbania cannabina-sweet sorghum mixed silage may help to improve fermentation quality and nutrient preservation.

Effect of tea polyphenols on the fermentation quality, protein preservation, antioxidant capacity and bacterial community of stylo silage

The present study was aimed to evaluate the improvement potential of tea polyphenols (TPP) on silage characteristics and bacterial community. Stylo ensiled with TPP (0, 0.2 or 0.4%, on a fresh basis) were analyzed for fermentation parameter, protein fraction, antioxidant activity and bacterial community after 7, 14, 30 and 60 days fermentation. The addition of TPP resulted in the decrease (P < 0.05) of pH values (5.09 vs. 4.91), dry matter loss (11.77 vs. 8.02% DM), butyric acid concentration (1.64 vs. 1.02% DM) and ammonia-N proportion (13.69 vs. 8.98% CP, on Day 30) of stylo silage as well as the increase (P < 0.01) of lactic acid bacteria population (6.17 vs. 7.54 cfu/g FM) and true protein content (6.03 vs. 7.44% DM), particularly at the first 30 days of ensiling. It somewhat enhanced the antioxidant capacity of style silage at the early stage, and altered the bacterial community of stylo silage, with Clostridium_sensu_stricto_1 and Lachnoclostridium_5 much decreased but Enterobacter and Clostridium still being the dominant genera. It is suggested that TPP could help improve fermentation quality and nutrient preservation of stylo silage, and delay proteolysis process and antioxidant decay.

Effects of intrinsic tannins on proteolysis dynamics, protease activity, and metabolome during sainfoin ensiling

Condensed tannins (CT) from sainfoin have a high capacity to inhibit proteolysis. A previous study reported that CT from sainfoin can inhibit lactic acid bacteria activity and decrease ammonium-nitrogen (N) content during sainfoin ensiling; however, no study has focused on the metabolome of ensiled sainfoin. The objective of the present study was to investigate the effects of CT [following supplementation of deactivated CT with polyethylene glycol (PEG)] on protease activity, keystone bacteria, and metabolome during sainfoin ensiling. According to the results, PEG amendment increased non-protein N, amino acid, and soluble protein contents significantly (in the 49.08-59.41, 116.01-64.22, and 23.5-41.94% ranges, respectively, p < 0.05) during ensiling, whereas neutral detergent-insoluble protein and acid detergent-insoluble protein were decreased significantly (in the 55.98-64.71 and 36.58-57.55% ranges, respectively, p < 0.05). PEG supplementation increased aminopeptidase and acid protease activity after 3 days of ensiling (p < 0.05) and increased carboxypeptidase activity during the entire ensiling process (p < 0.05). The keystone bacteria changed following PEG addition (Stenotrophomonas, Pantoea, and Cellulosimicrobium in the control vs. Microbacterium, Enterococcus, and Brevundimonas in the PEG-treated group). In total, 510 metabolites were identified after 60 days of sainfoin ensiling, with 33 metabolites annotated in the Kyoto Encyclopedia of Genes and Genomes database. Among the metabolites, phospholipids were the most abundant (72.7% of 33 metabolites). In addition, 10 upregulated and 23 downregulated metabolites were identified in the PEG-treated group when compared with the control group, after 60 days of ensiling (p < 0.05). Pediococcus (correlated with 20 metabolites, R 2 > 0.88, p < 0.05) and Lactobacillus (correlated with 16 metabolites, R 2 > 0.88, p < 0.05) were the bacteria most correlated with metabolites. The results suggested antagonistic effects between Lactobacillus and Pediococcus during ensiling. The decreased proteolysis during sainfoin ensiling was mainly attributed to the inhibition of protease activity by CT, particularly carboxypeptidase activity. In addition, proteolysis decreased partly due to CT inhibiting Pediococcus activity during ensiling, with Pediococcus being significantly and positively correlated with dopamine after 60 days of ensiling (R 2 = 0.8857, p < 0.05).

Effects of Pyroligneous Acid on Diversity and Dynamics of Antibiotic Resistance Genes in Alfalfa Silage

Antibiotic resistance genes (ARGs) are recognized as contaminants due to their potential risk for human and environment. The aim of the present study is to investigate the effects of pyroligneous acid (PA), a waste of biochar production, on fermentation characteristics, diversity, and dynamics of ARGs during ensiling of alfalfa using metagenomic analysis. The results indicated that PA decreased (P < 0.05) dry matter loss, pH value, gas production, coliform bacteria count, protease activity, and nonprotein-N, ammonia-N, and butyric acid contents and increased (P < 0.05) lactic acid content during ensiling. During fermentation, Bacteria, Firmicutes, and Lactobacillus were the most abundant at kingdom, phylum, and genus levels, respectively. Pyroligneous acid reduced the relative abundance of Bacteria and Firmicutes and increased that of Lactobacillus. The detected ARGs belonged to 36 drug classes, including mainly macrolides, tetracycline, lincosamides, and phenicol. These types of ARGs decreased during fermentation and were further reduced by PA. These types of ARGs were positively correlated (P < 0.05) with fermentation parameters like pH value and ammonia-N content and with bacterial communities. At the genus level, the top several drug classes, including macrolide, tetracycline, lincosamide, phenicol, oxazolidinone, streptogramin, pleuromutilin, and glycopeptide, were positively correlated with Staphylococcus, Streptococcus, Listeria, Bacillus, Klebsiella, Clostridium, and Enterobacter, the potential hosts of ARGs. Overall, ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community composition. Ensiling could be a feasible way to mitigate ARGs in forages. The addition of PA could not only improve fermentation quality but also reduce ARG pollution of alfalfa silage.

IMPORTANCE Antibiotic resistance genes (ARGs) are considered environmental pollutants posing a potential human health risk. Silage is an important and traditional feed, mainly for ruminants. ARGs in silages might influence the diversity and distribution of ARGs in animal intestinal and feces and then the manure and the manured soil. However, the diversity and dynamics of ARGs in silage during fermentation are still unknown. We ensiled alfalfa, one of the most widely used forages, with or without pyroligneous acid (PA), which was proved to have the ability to reduce ARGs in soils. The results showed that ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community. The majority of ARGs in alfalfa silage reduced during fermentation. The addition of PA could improve silage quality and reduce ARG pollution in alfalfa silage. This study can provide useful information for understanding and controlling ARG pollution in animal production.

Effects of applying cellulase and starch on the fermentation characteristics and microbial communities of Napier grass (Pennisetum purpureum Schum.) silage

This study investigated the effects of applying cellulase and starch on the fermentation characteristics and microbial communities of Napier grass silage after ensiling for 30 d. Three groups were studied: No additives (control); added cellulase (Group 1); and added cellulase and starch (Group 2). The results showed that the addition of cellulase and starch decreased the crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and pH significantly (p < 0.05) and increased water-soluble carbohydrate (WSC) content (p < 0.05). The addition of additives in two treated groups exerted a positive effect on the lactic acid (LA) content, lactic acid bacteria (LAB) population, and lactic acid / acetic acid (LA/AA) ratio, even the changes were not significant (p > 0.05). Calculation of Flieg’s scores indicated that cellulase application increased silage quality to some extent, while the application of cellulase and starch together significantly improved fermentation (p < 0.05). Compared with the control, both additive groups showed increased microbial diversity after ensiling with an abundance of favorable bacteria including Firmicutes and Weissella, and the bacteria including Proteobacteria, Bacteroidetes, Acinetobacter increased as well. For alpha diversity analysis, the combined application of cellulase and starch in Group 2 gave significant increases in all indices (p < 0.05). The study demonstrated that the application of cellulase and starch can increase the quality of Napier grass preserved as silage.

Effects of Vanillic Acid on Dynamic Fermentation Parameter, Nitrogen Distribution, Bacterial Community, and Enzymatic Hydrolysis of Stylo Silage

Vanillic acid (VA) is a phenolic acid derivative commonly found in plants and foods, with a pleasant creamy odor and pharmacologic activities, which is hypothesized to help improve silage fermentation. The silage profile of stylo silage ensiled with addition of VA was evaluated. The results showed that VA addition resulted in the decrease of pH value (5.22 vs. 4.33), dry matter loss (5.37 vs. 2.51% DM), and ammonia-N proportion (14.57 vs. 1.51% CP) of stylo silage as well as the increase of lactic acid concentration (0.51 vs. 1.17% DM), true protein proportion (51.18 vs. 58.47% CP), and saccharification yield (113.64 vs. 126.40 mg/g DM). Meanwhile, bacterial community of stylo silage was altered, where the relative abundance of Enterobacter, Clostridium, and Kosakonia decreased and that of Commensalibacter and Methylobacterium increased. In conclusion, it is suggested that VA could be used as a novel silage additive to improve silage fermentation and nutrient preservation of stylo silage.

Citric Acid Influences the Dynamics of the Fermentation Quality, Protease Activity and Microbial Community of Mulberry Leaf Silage

Mulberry (Morus alba) leaves has performed well as a high-quality protein supplement for livestock and enriches the edible resources of livestock. However, the harvest of mulberry leaves is seasonal and occurs mainly during the rainy season in southeast China; therefore, humid and sultry weather causes serious losses of mulberry leaf biomass, which pose a challenge for the preservation of mulberry leaves. In this study, we used the silage fermentation method to preserve mulberry leaves and investigated the effects of citric acid on the silage quality of mulberry leaves. Mulberry leaves were ensiled with or without 1% citric acid and 2% citric acid. The chemical composition, protein fraction and microbial community of mulberry leaf silages were analyzed. The results showed that the silage treated with citric acid had a higher dry matter recovery and lactic acid content and a lower acetic acid content, non-protein nitrogen content and ammonia-N content; citric acid also inhibited the activities of carboxypeptidase and aminopeptidase. Moreover, citric acid increased Lactobacillus abundance in silages and decreased the abundance of undesired microorganisms, such as Enterobacter. In summary, the addition of citric acid improved the fermentation quality of mulberry leaf silages, with 2% citric acid being more effective than 1% citric acid.

Influence of Pyroligneous Acid on Fermentation Parameters, CO2 Production and Bacterial Communities of Rice Straw and Stylo Silage

Carbon dioxide (CO₂) is a primary greenhouse gas and the main cause of global warming. Respiration from plant cells and microorganisms enables CO₂ to be produced during ensiling, a method of moist forage preservation applied worldwide. However, limited information is available regarding CO₂ emissions and mitigation during ensiling. Pyroligneous acid, a by-product of plant biomass pyrolysis, has a strong antibacterial capacity. To investigate CO₂ production and the influence of pyroligneous acid, fresh stylo, and rice straw were ensiled with or without 1% or 2% pyroligneous acid. Dynamics of the fermentation characteristics, CO₂ production, and bacterial communities during ensiling were analyzed. Pyroligneous acid increased the lactic acid content and decreased the weight losses, pH, ammonia-N content, butyric acid content, and coliform bacterial numbers (all P < 0.05). It also increased the relative abundance of Lactobacillus and decreased the relative abundances of harmful bacteria such as Enterobacter and Lachnoclostridium. Adding pyrolytic acids reduced the gas production, especially of CO₂. It also increased the relative abundances of CO₂-producing bacterial genera and of genera with the potential for CO₂ fixation. In conclusion, adding pyroligneous acid improved the fermentation quality of the two silages. During ensiling, CO₂ production was correlated with bacterial community alterations. Using pyroligneous acid altered the bacterial community to reduce CO₂ production during ensiling. Given the large production and demand for silage worldwide, application of pyroligneous acid may be an effective method of mitigating global warming via CO₂ emissions.

Effects of Gallic Acid on Fermentation Parameters, Protein Fraction, and Bacterial Community of Whole Plant Soybean Silage

Whole plant soybean (WPS) is a kind of legume resource with characteristics of high nutrition, large biomass, and wide distribution. In the present study, we have investigated the feasibility and effects of gallic acid (GA) on WPS silage quality, nitrogen distribution, tannin content, and bacterial community. The 0.5 and 1% (fresh matter basis) GA were added into WPS for dynamic ensiling (days 3, 7, 14, and 30, respectively). The results showed that the WPS silage with GA addition significantly decreased pH value (6.16–5.38 at ensiling day 30), coliform bacteria count and butyric acid (65.3–62.0 g/kg dry matter at ensiling day 30), and amino nitrogen contents (259–88.2 g/kg total nitrogen at ensiling day 30) and promoted lactic acid (9.62–31.5 g/kg dry matter at ensiling day 30), acetic acid (24.1–85.6 g/kg dry matter at ensiling day 30), and tannin (total phenol and hydrolyzable tannin) contents. Additionally, the GA addition also contributed to the change of bacterial community, where Firmicutes and Lactobacillus were most abundant on phylum and genus levels, respectively. The above results suggested that GA additive applied in WPS silage was an effective strategy to protect nutrition and improve fermentation quality, and the 1% GA addition showed a better effect.

Altering bacterial community: A possible way of lactic acid bacteria inoculants reducing CO2 production and nutrient loss during fermentation

CO₂ production during ensiling is a source of greenhouse gases emissions and a cause of nutrient loss of silage. To investigate the influence of additives on CO₂ production and relevant bacterial communities, stylo and rice straw were ensiled with sucrose and Lactobacillus plantarum (LP). After 30 days fermentation, LP reduced CO₂ production (from 66.2 to 0 mL/100 g fresh matter in stylo, from 83.7 to 16.6 mL/100 g fresh matter in rice straw) and weight loss (from 2.71 to 1.72% in stylo, from 2.75 to 2.40% in rice straw). CO₂ production was positively correlated (P < 0.05) with Lactococcus (0.99), Leuconostoc (0.55), Lachnoclostridium (0.45), Prevotella (0.23) and was negatively correlated (P < 0.05) with Serratia (-0.66), Sphingobacterium (-0.58), Pediococcus (-0.36). LP decreased the relative abundance of genera positively correlated with CO₂ production and increased that of genera negatively correlated. In conclusion, LP could reduce CO₂ production by altering bacterial community during ensiling.

Effect of storage time and the level of formic acid on fermentation characteristics, epiphytic microflora, carbohydrate components and in vitro digestibility of rice straw silage

Objective

The study aimed to evaluate the effect of storage time and formic acid (FA) on fermentation characteristics, epiphytic microflora, carbohydrate components and in vitro digestibility of rice straw silage.

Methods

Fresh rice straw was ensiled with four levels of FA (0%, 0.2%, 0.4%, and 0.6% of fresh weight) for 3, 6, 9, 15, 30, and 60 d. At each time point, the silos were opened and sampled for chemical and microbial analyses. Meanwhile, the fresh and 60-d ensiled rice straw were further subjected to in vitro analyses.

Results

The results showed that 0.2% and 0.6% FA both produced well-preserved silages with low pH value and undetected butyric acid, whereas it was converse for 0.4% FA. The populations of enterobacteria, yeasts, moulds and aerobic bacteria were suppressed by 0.2% and 0.6% FA, resulting in lower dry matter loss, ammonia nitrogen and ethanol content (p<0.05). The increase of FA linearly (p<0.001) decreased neutral detergent fibre and hemicellulose, linearly (p<0.001) increased residual water soluble carbohydrate, glucose, fructose and xylose. The in vitro gas production of rice straw was decreased by ensilage but the initial gas production rate was increased, and further improved by FA application (p<0.05). No obvious difference of FA application on in vitro digestibility of dry matter, neutral detergent fibre, and acid detergent fibre was observed (p>0.05).

Conclusion

The 0.2% FA application level promoted lactic acid fermentation while 0.6% FA restricted all microbial fermentation of rice straw silages. Rice straw ensiled with 0.2% FA or 0.6% FA improved its nutrient preservation without affecting digestion, with the 0.6% FA level best.

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.

Abundance and diversity of epiphytic microbiota on forage crops and their fermentation characteristic during the ensiling of sterile sudan grass

This study aimed to evaluate the effects of exogenous epiphytic microbiota inoculation on the fermentation quality and microbial community of sudan grass silage. Gamma irradiated sudan grass was ensiled with distilled water (STR), epiphytic microbiota of sudan grass (SUDm), forage sorghum (FSm), napier grass (NAPm) and whole crop corn (WCCm). The FSm inoculated silage have significantly lower lactic acid (LA) concentration and higher pH during early ensiling, while LA concentration gradually and significantly increased with the progression of ensiling and have lower pH in relation to other treatments for terminal silage. Inoculation of NAPm resulted in lower LA and higher acetic acid (AA) concentrations, higher pH, ammonia-N and dry matter losses for terminal silage, followed by SUDm silage. Inoculations of WCCm significantly increased LA production and pH decline during early ensiling and have higher LA and pH then NAPm and SUDm silages during final ensiling. The early fermentation of SUDm silage was dominated by genus of Pediococcus. The genera of Lactobacillus were predominant in WCCm and NAPm silages during 3 days of ensiling, while Weissella dominated initial microbial community of FS silage. The terminal silage of NAPm was dominated by Enterobacter and Rosenbergiella, while Enterobacter and Lactobacillus dominated terminal SUDm silage. The final silage of FSm was dominated by Lactobacillus, Weissella and Pediococcus, while Lactobacillus and Acetobacter dominated terminal WCCm silages. The results demonstrated that among the four forages the epiphytic microbiota from forage sorghum positively influenced the microbial community and fermentability of sudan grass silage.

Physiological, Biochemical, and Transcriptomic Responses of Neolamarckia cadamba to Aluminum Stress

Aluminum is the most abundant metal of the Earth's crust accounting for 7% of its mass, and release of toxic Al3+ in acid soils restricts plant growth. Neolamarckia cadamba, a fast-growing tree, only grows in tropical regions with acidic soils. In this study, N. cadamba was treated with high concentrations of aluminum under acidic condition (pH 4.5) to study its physiological, biochemical, and molecular response mechanisms against high aluminum stress. High aluminum concentration resulted in significant inhibition of root growth with time in N. cadamba. The concentration of Al3+ ions in the root tip increased significantly and the distribution of absorbed Al3+ was observed in the root tip after Al stress. Meanwhile, the concentration of Ca, Mg, Mn, and Fe was significantly decreased, but P concentration increased. Aluminum stress increased activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase from micrococcus lysodeiktic (CAT), and peroxidase (POD) in the root tip, while the content of MDA was decreased. Transcriptome analysis showed 37,478 differential expression genes (DEGs) and 4096 GOs terms significantly associated with treatments. The expression of genes regulating aluminum transport and abscisic acid synthesis was significantly upregulated; however, the genes involved in auxin synthesis were downregulated. Of note, the transcripts of several key enzymes affecting lignin monomer synthesis in phenylalanine pathway were upregulated. Our results shed light on the physiological and molecular mechanisms of aluminum stress tolerance in N. cadamba.

Beneficial Effects of Tannic Acid on the Quality of Bacterial Communities Present in High-Moisture Mulberry Leaf and Stylo Silage

Tannic acid (TA), a type of polyphenol, is widely distributed in plants, especially in legumes. Not only does it possess antimicrobial properties, but it also has the ability to bind with proteins. The fermentation parameters, nitrogen fractions, antioxidant capacity, and bacterial communities present in mulberry leaves and stylo (Stylosanthes guianensis) ensiled with or without 1 and 2% TA per kilogram of fresh matter (FM) were investigated after 75 days’ fermentation. The results showed that 1 and 2% TA both significantly decreased the butyric acid content (4.39 and 7.83 g/kg dry matter (DM), respectively) to an undetectable level in both mulberry leaf and stylo silage. In addition, 2% TA significantly increased the contents of lactate (24.0–39.0 and 8.50–32.3 g/kg DM), acetate (18.0–74.5 and 9.07–53.3 g/kg DM), and the antioxidant capacity of both mulberry leaf and stylo silage, respectively. With the addition of 1 and 2% TA, the pH values (5.55–5.04 and 4.87, respectively) and ammonia-N (NH₃-N) content (85.5–27.5 and 16.9 g/kg total nitrogen (TN), respectively) were all significantly decreased in stylo silage. In addition, TA increased the relative abundance of Weissella, Acinetobacter, and Kosakonia spp. and decreased that of undesirable Clostridium spp. TA can thus be used to improve the silage quality of both mulberry leaf and stylo silage, with 2% TA being the better concentration of additive to use.

Effects of various epiphytic microbiota inoculation on the fermentation quality and microbial community dynamics during the ensiling of sterile Napier grass

AIM

To investigate epiphytic microbiota transformation of forages, their adaptation and contributions to fermentation quality of silage.

METHODS AND RESULTS

Gamma-irradiated chopped Napier grass were ensiled with distilled water (STR), extracted epiphytic microbiota of Napier grass (NAP), sudan grass (SUD), whole crop corn (WCC) and forage sorghum (FS). Inoculating Napier grass with WCC significantly increased lactic acid (LA) concentrations during the initial ensiling period followed by a decline after 30 days. Relative to other silages (except STR) inoculation with NAP resulted in lower LA and greater pH, ammonia-N and dry matter (DM) losses. Silage inoculated with FS and SUD maintained lower pH as well as higher (P < 0·05) LA concentrations after 60 days of storage. During day 3 of ensilage, WCC, NAP and SUD inoculated silage were dominated by bacterial genera of Lactobacillus, while Lactococcus dominated the FS silage. Final silages were dominated by Lactobacillus in all treatment silages, however Enterobacter (16·3%) in NAP and Acetobacter (25·7%) in WCC silage were also prominent during the final ensiling.

CONCLUSION

The inoculation of epiphytic microbiota of forage sorghum and sudan grass positively influenced the microbial community and fermentability of sterile Napier grass silage.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first time to investigate the effects of various epiphytic microbiota as silage inoculants which can be used as alternative source of environmental friendly and economically feasible silage additives.

Formic Acid as an Antimicrobial for Poultry Production: A Review

Organic acids continue to receive considerable attention as feed additives for animal production. Most of the emphasis to date has focused on food safety aspects, particularly on lowering the incidence of foodborne pathogens in poultry and other livestock. Several organic acids are currently either being examined or are already being implemented in commercial settings. Among the several organic acids that have been studied extensively, is formic acid. Formic acid has been added to poultry diets as a means to limit Salmonella spp. and other foodborne pathogens both in the feed and potentially in the gastrointestinal tract once consumed. As more becomes known about the efficacy and impact formic acid has on both the host and foodborne pathogens, it is clear that the presence of formic acid can trigger certain pathways in Salmonella spp. This response may become more complex when formic acid enters the gastrointestinal tract and interacts not only with Salmonella spp. that has colonized the gastrointestinal tract but the indigenous microbial community as well. This review will cover current findings and prospects for further research on the poultry microbiome and feeds treated with formic acid.

Effect on the ensilage performance and microbial community of adding Neolamarckia cadamba leaves to corn stalks

To comprehensively evaluate the fermentation performance and microbial community of corn stalks (CS) silage mixed with Neolamarckia cadamba leaves (NCL), CS were ensiled with four levels (0%, 10%, 30% and 50% of fresh weight) of NCL for 1, 7, 14, 30, 60 days in two trials. The results showed that all silages were well preserved with low pH (3.60-3.88) and ammonia nitrogen content (0.08-0.19% DM). The silage samples with NCL displayed lower (P < 0.05) acetic acid, propionic acid and ammonia nitrogen contents and lactic acid bacteria population during ensiling than control silages (100% CS). The addition of NCL also influenced the distribution of bacterial and fungal communities. Fungal diversity (Shannon's indices were 5.15-5.48 and 2.85-4.27 in trial 1 and trial 2 respectively) increased while the relative abundances of Lactobacillus, Leuconostocs, Acetobacter and two moulds (Aspergillus and Fusarium) decreased after added NCL. In summary, mixing NCL is a promising effective approach to preserve protein of CS silage and inhibit the growth of undesirable bacteria and mould, thus to improve the forage quality to some extent.

Metagenomic analysis revealed the succession of microbiota and metabolic function in corncob composting for preparation of cultivation medium for Pleurotus ostreatus

Metagenomic sequencing was used to reveal the dynamic changes in microbiota and the metabolic functions in corncob composting for preparing cultivation medium of Pleurotus ostreatus. Results showed that the changes of physicochemical properties lead to different dominant phylum at different stages of composting. Firmicutes replaced Proteobacteria as the dominant phylum at thermophilic stage. Correlation analysis indicated that the succession of microbiota was significantly affected by the C/N ratio, pH, temperature and organic matters in compost. The changes in community inevitably lead to the differences of metabolic functions. Metabolism analysis indicated that carbohydrate, lipid and amino acid metabolism were relatively higher in thermophilic stage. Conversely, the metabolism of starch, sucrose, galactose, ascorbate was mainly detected in the late stage. The metabolisms of different stages were driven by different microorganisms. Overall, these findings deepened our understanding of metabolic functions, and it is of great value to the metabolomics research of composting system.

Dynamics of fermentation quality, physiochemical property and enzymatic hydrolysis of high-moisture corn stover ensiled with sulfuric acid or sodium hydroxide

A better understanding of biomass usability during storage would offer basis for management decisions in production. High-moisture corn stover was ensiled with sulfuric acid (H₂SO₄, 0.3% and 0.6%) or sodium hydroxide (NaOH, 0.5% and 1.0%) and ensiling characteristics, lignocellulosic profile and enzymatic saccharification were investigated on day 3, 7, 15, 30 and 60 of ensiling. The results showed that 0.6% H₂SO₄ reduced dry matter loss (9.81% to 6.34%) and ammonia-N content (3.89 to 1.04 g/kg DM) during ensiling, whereas it was converse for NaOH treatment (19.89%, 5.74 g/kg DM). Hemicellulose was reduced (27.98% to 22.61%, 16.81% DM) by 0.6% H₂SO₄ or 1.0% NaOH. Saccharification yield was decreased (306 to 229 mg/g DM) during ensiling, which was improved (229 to 356, 277 mg/g DM) by H₂SO₄ and NaOH treatments. This study suggests that ensiling with addition of 0.6% H₂SO₄ could improve nutrient preservation and saccharification yield of high-moisture corn stover.

Improving fermentation, protein preservation and antioxidant activity of Moringa oleifera leaves silage with gallic acid and tannin acid

Whether tannins reducing proteolysis is related to protease or the antioxidant capacity could be preserved during Moringa oleifera leaves (MOL) ensiling are unclear. In the present study, MOL ensiled with 1% and 2% gallic acid (GA) or tannic acid (TA) were analyzed for fermentation parameters, protein fractions, protease activities and antioxidant capacity on day 3, 7, 14 and 30 of ensiling. The results showed that GA and TA decreased dry matter loss (11.13% vs 8.35% and 3.11%, in the level of 2%) and proteolysis (nonprotein-N: 56.31% vs 32.64% and 26.04% TN). Meanwhile, GA and TA increased pH, yeasts number, ammonia-N content and aminopeptidase activity. The antioxidant capacity of MOL silage gradually increased during ensiling, and was dramatically enhanced by the addition of GA and TA. In conclusion, this study suggests that GA and TA could help to improve the preservation of protein and antioxidant capacity during MOL ensiling.