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The seasonal surplus and putrefactive property of moist forages inevitably increase the pressure on environmental protection and residual grass disposal. In the current work, the anaerobic fermentation approach was adopted to assist the sustainable recycling of leftover Pennisetum giganteum (LP), and its chemical composition, fermentation performance, bacterial community and functional profiles during anaerobic fermentation were studied. Fresh LP was spontaneously fermented for up to 60 d. At the end of anaerobic fermentation, fermented LP (FLP) displayed homolactic fermentation with low pH value, ethanol, and ammonia nitrogen concentrations but high lactic acid concentration. Weissella was dominant in 3-day FLP, yet Lactobacillus was the overwhelming genus (92.6%) in 60-day FLP. The anaerobic fermentation process promoted (P < 0.05) the metabolism of carbohydrate and nucleotide while suppressing (P < 0.05) that of lipid, cofactors, vitamins, energy, and amino acid. The results showed that the residual grass with LP as an example could be successfully fermented even if no additives were added, without signs of clostridial and fungal contamination. [ABSTRACT FROM AUTHOR]

Biomass microbiota and chemical constituent are closely associated with final anaerobic fermentation performance. But the limiting factors affecting anaerobic fermentation quality and bacterial community have been rarely explored. This study aimed to elucidate the relative contribution of initial microbiota and chemical constituent of sweet sorghum on its final anaerobic fermentation quality. Sweet sorghum at two developmental stages (heading-stage, G1; hard-dough-stage, G2) was treated as follows: G1 microbiota + sterilized G1 (M1C1), G2 microbiota + sterilized G1 (M2C1), G1 microbiota + sterilized G2 (M1C2), and G2 microbiota + sterilized G2 (M2C2). The results showed that chemical constituent rather than microbiota changes remarkably influenced the production of lactic acid, propionic acid and ammonia-N, the relative abundance of Lactobacillus, Weissella, Lactococcus, Pediococcus, and Pantoea of sweet sorghum after anaerobic fermentation. The chemical constituent was the key limiting factor affecting the anaerobic fermentation quality of sweet sorghum. This study could provide a reference for clarifying the key limiting factors affecting anaerobic fermentation and making recommendations for production. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the effects of delayed harvest and storage length on fermentation products, bacterial community, and metabolic shifts of elephant grass silage. The late-harvested elephant grass (LG) was naturally fermented (NLG) for 1, 3, 7, 15, 30, and 60 days, respectively. After 60-day ensiling, NLG displayed homolactic fermentation with low pH value, butyric acid, and ammonia nitrogen concentrations, and high lactic acid concentration, and ratio of lactic acid to acetic acid. Pseudomonas, Sphingomonas , and Pantoea dominated the bacterial community in LG, but Lactobacillus, Lactococcus , and Pediococcus were the advantageous genera in a 3-day and 60-day NLG. The correlation heatmap revealed that Acetobacter was positively related to acetic acid, ethanol, ammonia nitrogen, and butyric acid concentrations. There were distinct differences in the KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic profiles of fresh and ensiled LG. Ensiling suppressed the metabolism of amino acid, vitamins, and energy, while promoted the metabolism of carbohydrate. The LG can be well-fermented without additives, but its low crude protein content should not be ignored when applied in agricultural practice. The ensiling process remarkably affected the fermentation quality, bacterial community, and metabolic profiles of NLG. [ABSTRACT FROM AUTHOR]

This study investigated the effects of developmental stage and store time on the chemical composition, microbial community, co-occurrence networks and fermentation characteristics of sweet sorghum silage. Sweet sorghum harvested at two developmental stages (heading stage, S1; hard dough stage, S2) was treated as follows: (I) natural fermentation of S1 (NS1); (II) natural fermentation of S2 (NS2) and ensiled for 1, 3, 7, 15, 30 and 60 days. After 60 days of ensiling, NS2 silage had higher lactic acid concentration and the ratio of lactic to acetic acid, and lower pH value and acetic acid concentration than NS1 silage. Meanwhile, NS2 silage also had higher ammonia nitrogen (NH3-N) content than NS1 silage, but the NH3-N content of both treatments was lower than 100 g/kg TN. Leuconostoc and Lactococcus were respectively dominant in both 7-day NS1 and NS2 silages, while Lactobacillus was the most abundant genus in 30-day NS1 and NS2 silages. The developmental stage altered the bacterial co-occurrence networks of fresh and ensiled sweet sorghum. Spearman's correlation heatmap showed that the higher lactic acid content and ratio of lactic to acetic acid in NS2 silage could be associated with the higher water-soluble carbohydrate content in S2 material, the higher abundance of Lactococcus in the initial phase of ensiling and the higher abundance of Lactobacillus in the late phase of ensiling. These results concluded that the sweet sorghum harvested at the hard dough stage is preferred for silage production over the sweet sorghum harvested at the heading stage. Microbial succession pattern was studied on fresh and ensiled samples. Growth stage affected the chemical and microbial parameters of sweet sorghum. Epiphytic microbiota was correlated with the chemical composition of forage. Metagenomic sequencing showed Lactobacillus was dominated in all silages. Growth stage accelerated the fermentation of sweet sorghum silage. [ABSTRACT FROM AUTHOR]

In this study, the anaerobic fermentation technique was conducted to accomplish the clean recycling of surplus napiergrass. The surplus napiergrass harvested at two harvest dates (early vegetative stage, NI; late vegetative stage, NII) was treated as follows: (i) natural fermentation of NI (NNI); (ii) natural fermentation of NII (NNII) and stored for 1, 3, 7, 15, 30 and 60 days. After 60 days of anaerobic fermentation, NNI had higher lactic acid concentration and ratio of lactic to acetic acid, but lower pH value and ammonia–nitrogen concentration than NNII. Lactobacillus and Enterobacter were, respectively, dominant in both 7-day NNI and NNII, while Lactobacillus was the most abundant genus in 30-day NNI and NNII. Both harvest date and store time altered the bacterial co-occurrence networks of fresh and fermented napiergrass. The complexity of the bacterial networks decreased from NII, NI, NNII to NNI. The correlations were primarily positive in the bacterial networks of NI, NII, NNII-7 and NNII-30 with positive correlative proportion of 53.0%, 64.3%, 53.1% and 55.6%, but negative in those of NNI-7 (47.4%) and NNI-30 (46.2%) with positive correlative proportion of 47.4% and 46.2%, respectively. Overall, the fermentation quality and microbial community structure of napiergrass during anaerobic fermentation were highly influenced by harvest date and store time. Based on the principle of stable fermentation and high quality, anaerobic fermentation of NI for at least 15 days is recommended. The in-depth understanding of microbial community dynamics and co-occurrence networks during anaerobic fermentation of napiergrass is important for revealing the fermentation mechanism and can contribute to resource recycling without increasing cost. [ABSTRACT FROM AUTHOR]