Intrinsic tannins affect ensiling characteristics and proteolysis of Neolamarckia cadamba leaf silage by largely altering bacterial community.

The mechanism that tannins alter microbial community to inhibit proteolysis and enhance silage quality is unclear. Neolamarckia cadamba leaf (NCL; rich in tannins) were ensiled alone or with addition of polyethylene glycol (PEG, tannins inactivator), and then fermentation quality, proteolysis activity and bacterial community were investigated during ensiling (Day 3, 7, 14 and 30). As a result, PEG addition increased lactic acid (1.09% vs 2.03%, on dry matter basis) and nonprotein-N (13.65% vs 17.59%, on crude protein basis) contents but decreased ammonia-N content (9.21% vs 2.29%, on crude protein basis) in NCL silage. Meanwhile, the dominant microbiome shifted from Cyanobacteria (60.92%-81.50%) to Firmicutes (48.96%-88.67%), where the unclassified genus (80.95%-85.71%) was substituted by Leuconstoc (42.03%-55.55%) and subsequently Lactobacillus (65.98%-82.43%). This study suggests that the intrinsic tannins inhibit lactic acid fermentation and protein degradation in NCL silage.

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.

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.

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.

Ensiling characteristics, physicochemical structure and enzymatic hydrolysis of steam-exploded hippophae: Effects of calcium oxide, cellulase and Tween.

To find a comprehensive way to enhance the utilizability of steam-exploded hippophae, calcium oxide (CaO) preimpregnation, cellulase-added storage and saccharification with addition of Tween 20 were investigated in this study. Both CaO preimpregnation and cellulase addition promoted the ensiling fermentation of anaerobically stored steam-exploded hippophae indicated by lower cellulose proportion and higher organic acids content, but led to the decrease of saccharification yield by 11.83% and 46.77-51.22%, respectively. When taking into account of organic acids being utilizable energy source, storing with addition of cellulase enhanced the utilizability of the materials in whole. Moreover, the addition of Tween 20 enhanced saccharification yield of the steam-exploded hippophae by 26.69-45.25%. Additionally, FTIR and XRD spectra clearly illustrated the structural alteration during storage. It is concluded that storing with addition of cellulase and hydrolyzing with addition of Tween 20 can enhance the utilizability of steam-exploded hippophae.

Effects of citric acid on fermentation characteristics and bacterial diversity of Amomum villosum silage.

To study the effects of citric acid on fermentation process of Amomum villosum silage, A. villosum was ensiled without or with 1%, 2% citric acid and fermentation parameters and bacterial diversity were analyzed after 3, 7, 14, 30 days ensiling, respectively. Citric acid treated silages had lower dry matter loss (1.83% vs 2.23%), pH (3.84 vs 6.02), ammonia-N (0.33 vs 1.79 g/kg DM) and coliform bacteria number (<2.00 vs 7.27 log10 CFU/g FM) than the control after 30 days ensiling. The relative abundance of lactic acid bacteria, Pediococcus and Lactobacillus increased, whereas undesirable microorganisms like Enterobacter, Escherichia-Shigella and Pantoea decreased in citric acid treated A. villosum silage. These results indicated that quality A. villosum silage could be obtained by citric acid addition.

Gallic acid influencing fermentation quality, nitrogen distribution and bacterial community of high-moisture mulberry leaves and stylo silage.

To investigate the feasibility of vegetal gallic acid (GA) improving silage quality, fermentation parameter, nitrogen distribution and bacterial community of mulberry leaves and stylo ensiled with 1% and 2% GA were analyzed after 60-d fermentation. The results showed that GA addition decreased dry matter loss (6.08% vs 5.35%, 17.79% vs 11.56% in mulberry leaves and style silage, respectively), pH (6.51 vs 5.98, 5.55 vs 4.57), butyric acid (0.41% and 0.83% DM, undetected in GA groups) and ammonia-N (0.71% vs 0.19%, 1.46% vs 0.29% TN) contents and increased lactic acid (2.27% vs 6.68%, 0.91% vs 1.91% DM) and acetic acid (1.68% vs 3.20%, 0.97% vs 2.02% DM) contents. Meanwhile, the relative abundance of Clostridium or Enterobacter was decreased, and that of lactate-producing bacteria was increased in mulberry leaves and stylo silage. In conclusion, GA could be used as a green additive to improve fermentation quality and protein preservation during ensiling.

The nutrients in Moringa oleifera leaf contribute to the improvement of stylo and alfalfa silage: Fermentation, nutrition and bacterial community.

Moringa oleifera leaf (MOL) has been proved to improve silage fermentation but the exact reason is unclear yet. Fermentation quality, protein preservation, antioxidant activity and bacterial community of stylo and alfalfa ensiled with 5%, 10% dry MOL, stylo or alfalfa were investigated. The present results showed that mixing MOL led to the decrease of pH (5.15 vs 4.76, 5.71 vs 4.57 for stylo and alfalfa, respectively), butyric acid (15.1, 28.3 g/kg DM vs not detected), ammonia-N (111 vs 50.7, 351 vs 100 g/kg total N) contents, and the increase of lactic acid content (8.70 vs 13.0, 0.23 vs 14.0 g/kg DM) and antioxidant activity relative to the control. The relative abundance of Clostridium was lowered (55.4% to 1.69%, 8.34% to 0.57%), whereas Lactobacillus was increased (14.9% to 63.2%, 11.7% to 23.5%). In conclusion, nutrients in MOL help to improve protein preservation and nutritional value of high-moisture stylo and alfalfa silage.