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

CO2 agitation combined with magnetized biochar to alleviate "ammonia inhibited steady-state": Exploring the mechanism by combining metagenomics with macroscopic indicators

The "ammonia inhibited steady-state" phenomenon is frequently observed in the anaerobic digestion (AD) process of nitrogen-rich substrates. Reconfiguring microbial ecosystems has proven to be an effective strategy for mitigating ammonia inhibition. In the current study, biochars were screened and targeted for modification. CO2 agitation combined with magnetized biochar was used to aid the semi-continuous AD systems with "ammonia inhibited steady-state." The results indicated that coconut shell biochar had the best stimulating effect on AD performance. The content of oxygen-containing functional groups (OCFGs), which had a positive correlation with the electron donating capacity (EDC), was targeted to be regulated. This strategy significantly increased the CH4 yield by 31.7 % (from 344 to 278 mL/g VS) (p < 0.05). Isotope tracing and KEGG gene annotation indicated that this strategy stimulated the efficiency of the hydrogenotrophic pathway. Simultaneously, it accelerated the attachment of microorganisms, which made the DIET pathway between bacteria and archaea efficient. Under CO2 agitation, the attachment of functional microorganisms to the biochar accelerated. Biochar weakened the synthesis of bioelectronic carriers (Cyt-c and chemosensory pili), while the electroactivity of the AD system was enhanced. This means that biochar replaced bioelectronic carriers and improved the DIET efficiency. In addition, the strategy had a positive effect on the colonization of simultaneous nitrification-denitrifying bacteria (Georgenia), which led to a decrease in ammonia nitrogen concentrations. This study revealed the mechanism by which this strategy alleviates ammonia inhibition and provided a promising strategy for the efficient AD of nitrogen-rich substrates.

Novel strategy to understand the bacteria-enzyme synergy action regulates the ensiling performance of wheat straw silage by multi-omics analysis

BACKGROUND

Ensiling technology shows promise for preserving and providing high-quality forage. However, the high polymeric content and compact properties of fiber result in low biodigestibility. This study aimed to evaluate the use of ensiling technology for storing wheat straw. It also analyzed changes in fermentation-related products, chemical components, bacterial communities, and metabolite profiles of wheat straw ensiled with or without cellulase or Lactiplantibacillus plantarum (L. plantarum).

RESULTS

The results showed that inoculation with L. plantarum, either alone or with cellulase, produced abundant organic acids, degraded fiber, suppressed most microbes, and increased certain metabolites in wheat straw silage. Wheat straw inoculated with L. plantarum, either alone or with cellulase, exhibited significantly lower neutral detergent fiber and acid detergent fiber contents compared to the control treatment. Additionally, higher lactic acid and acetic acid contents were observed in these treatments. The microbiome analysis revealed that Lactobacillus was dominant, while Kosakonia was suppressed. Metabolic analysis showed a significant increase in amino acids, peptides, analogues, and organic acid derivatives.

CONCLUSIONS

Overall, wheat straw inoculated with L. plantarum, either alone or with cellulase, produced well-preserved silage, providing new insights into recycling and utilizing wheat straw through bacterial-enzyme synergy.

Microbiome and response surface methodology analyses reveal Acetobacter pasteurianus as the core bacteria responsible for aerobic spoilage of corn silage (Zea mays) in hot and humid areas

Introduction

Weak aerobic stability is a notable challenge for whole-plant corn silage, particularly in hot and humid regions. Acetobacter is commonly regarded as an indicator of aerobic deterioration in silage, yet its precise role in fermentation and during aerobic exposure, as well as the factors that promote its growth, remain insufficiently understood.

Methods

In this study, whole-plant corn silage was prepared using a bagged method with controlled dry matter (DM) content at 20%, 25%, and 30%, and initial concentrations of A. pasteurianus at 40%, 50%, and 60%. The silage was stored for 60 days under varying temperatures (20°C, 30°C, and 40°C). Following the anaerobic storage phase, the silage was exposed to air at room temperature (20-25°C) for 7 days, both with and without A. pasteurianus inoculation.

Results

The results demonstrated that A. pasteurianus did not impact the nutritional value of the silage during anaerobic fermentation, maintaining a low pH (< 3.80). However, during aerobic exposure, the presence of A. pasteurianus significantly reduced the aerobic stability of the silage. The microbial community shifted from primarily Klebsiella species initially to Lactobacillus and Acetobacter species post-ensiling. During the aerobic exposure phase, A. pasteurianus and A. fabarum became the dominant species. Response Surface Methodology (RSM) analysis identified optimal conditions for the proliferation of A. pasteurianus during the aerobic phase, which occurred at 28°C, 25% DM, and 52% initial concentration at 3 ml/kg.

Discussion

These findings confirm that A. pasteurianus plays a critical role in reducing the aerobic stability of whole-plant corn silage. Additionally, the study identifies the optimal conditions that favor the proliferation of A. pasteurianus, offering valuable insights for the development of strategies to prevent and control this bacterium, thereby improving the aerobic stability of silage in hot and humid regions.

Biochar derivation at low temperature: A novel strategy for harmful resource usage of antibiotic mycelial dreg

Antibiotic mycelial dreg (AMD) has been categorized as hazardous waste due to the high residual hazardous contaminants. Inappropriate management and disposal of AMD can cause potential environmental and ecological risks. In this study, the potential of pleuromutilin mycelial dreg (PMD) as a novel feedstock for preparing tetracycline hydrochloride (TC) adsorbent was explored to achieve safe management of PMD. The results suggested that residual hazardous contaminants were completely eliminated after pyrolysis. With the increase of pyrolysis temperature, the yields, H/C, O/C, (O + N)/C, and pore size in PMD-derived biochars (PMD-BCs) decreased, while BET surface area and pore volume increased, resulting in the higher stability of the PMD-BCs prepared from higher temperatures. The TC adsorption of the PMD-BCs increased from 27.3 to 46.9 mg/g with the increase of the pyrolysis temperature. Surprisingly, pH value had a strong impact on the TC adsorption, the adsorption capacity of BC-450 increased from 6.5 to 71.1 mg/g when the solution pH value increased from 2 to 10. Lewis acid-base interaction, pore filling, π-π interaction, hydrophobic interaction, and charge-assisted hydrogen bond (CAHB) are considered to drive the adsorption. This work provides a novel pathway for the concurrent detoxification and reutilization of AMD.

Iron-modified biochar boosts anaerobic digestion of sulfamethoxazole pharmaceutical wastewater: Performance and microbial mechanism

The accumulation of volatile fatty acids (VFAs) caused by antibiotic inhibition significantly reduces the treatment efficiency of sulfamethoxazole (SMX) wastewater. Few studies have been conducted to study the VFAs gradient metabolism of extracellular respiratory bacteria (ERB) and hydrogenotrophic methanogen (HM) under high-concentration sulfonamide antibiotics (SAs). And the effects of iron-modified biochar on antibiotics are unknown. Here, the iron-modified biochar was added to an anaerobic baffled reactor (ABR) to intensify the anaerobic digestion of SMX pharmaceutical wastewater. The results demonstrated that ERB and HM were developed after adding iron-modified biochar, promoting the degradation of butyric, propionic and acetic acids. The content of VFAs reduced from 1166.0 mg L^-1 to 291.5 mg L^-1. Therefore, chemical oxygen demand (COD) and SMX removal efficiency were improved by 22.76% and 36.51%, and methane production was enhanced by 6.19 times. Furthermore, the antibiotic resistance genes (ARGs) such as sul1, sul2, intl1 in effluent were decreased by 39.31%, 43.33%, 44.11%. AUTHM297 (18.07%), Methanobacterium (16.05%), Geobacter (6.05%) were enriched after enhancement. The net energy after enhancement was 0.7122 kWh m^-3. These results confirmed that ERB and HM were enriched via iron-modified biochar to achieve high efficiency of SMX wastewater treatment.

Effect of temperature and storage methods on liquid digestate: Focusing on the stability, phytotoxicity, and microbial community

Identifying the stability and phytotoxicity of liquid digestate (LD) is necessary for safe agricultural utilization. Storage temperature, method, and time are critical factors that affect the stability and phytotoxicity of LD. This study therefore aimed to explore the dynamics of stability, phytotoxicity, and microbial community of LD in cattle farms under different storage conditions. The results showed that the contents of solids, organic matter, nitrogen, and phosphorous decreased during storage and exhibited temperature dependency. Conversely, the seed germination index increased, which was negatively correlated with dissolved organic carbon and ammonium nitrogen and positively correlated with certain bacteria (Thermovirga and Fastidiosipila). Open storage and/or higher temperature were found to contribute to the stabilization efficiency and phytotoxicity disappearance of LD. Open storage of LD at 30 °C for 60 days and 20 °C for 90 days was safe for its agricultural utilization, while hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days was safe. However, for storage at 10 °C for 180 days, additional post-treatment is required.

Effects of Different Types of LAB on Dynamic Fermentation Quality and Microbial Community of Native Grass Silage during Anaerobic Fermentation and Aerobic Exposure

Silage of native grasses can alleviate seasonal forage supply imbalance in pastures and provide additional sources to meet forage demand. The study aimed to investigate the effects of Lactobacillus plantarum (LP), Lactobacillus buchneri (LB), and Lactobacillus plantarum in combination with Lactobacillus buchneri (PB) on the nutritional quality, fermentation quality, and microbial community of native grass silage at 2, 7, 15, and 60 days after ensiling and at 4 and 8 days after aerobic exposure. The results showed that dry matter content, crude protein content, the number of lactic acid bacteria, and lactic acid and acetic acid content increased and pH and ammonia nitrogen content decreased after lactic acid bacteria (LAB) inoculation compared with the control group (CK). LP had the lowest pH and highest lactic acid content but did not have greater aerobic stability. LB maintained a lower pH level and acetic acid remained at a higher level after aerobic exposure; aerobic bacteria, coliform bacteria, yeast, and molds all decreased in number, which effectively improved aerobic stability. The effect of the compound addition of LAB was in between the two other treatments, having higher crude protein content, lactic acid and acetic acid content, lower pH, and ammonia nitrogen content. At the phylum level, the dominant phylum changed from Proteobacteria to Firmicutes after ensiling, and at the genus level, Lactiplantibacillus and Lentilactobacillus were the dominant genera in both LAB added groups, while Limosilactobacillus was the dominant genus in the CK treatment. In conclusion, the addition of LAB can improve native grass silage quality by changing bacterial community structure. LP is beneficial to improve the fermentation quality in the ensiling stage, LB is beneficial to inhibit silage deterioration in the aerobic exposure stage, and compound LAB addition is more beneficial to be applied in native grass silage.