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Anaerobic fermentation of corn straw with rumen microorganisms as inoculum to produce volatile fatty acids (VFAs) is important for biomass valorization. In this study, dynamic variation in bacterial and fungal community composition, carbohydrate-active enzymes (CAZymes) and key functional genes related with VFA production was explored via metagenomic sequencing. Rumen microorganisms efficiently hydrolyzed and acidified corn straw, and VFA concentration reached 8.99 g/L in 72 h. Bacterial and fungal community significantly changed, but the core genera kept stable. Low pH and VFA accumulation were the main factors affecting bacterial and fungal communities. The positive correlations between bacteria were more complex than those between fungi. Most CAZyme abundance significantly decreased after 72 h fermentation, and functional gene abundance participating in VFA generation also decreased. This study provided new insights into dynamic variation of bacteria and fungi during anaerobic ruminal fermentation in vitro, promoting the application of rumen microorganisms in practice.

The estuarine wetland buffer zone of the Fuhe river plays an important role in terms of improving water quality of Baiyangdian lake. In this study, the water purification effect and microbial community composition of an estuarine wetland buffer zone during a low-temperature period were investigated (March, 2021). The results indicated that the pre-sedimentation ecological pond (Pep), the subsurface flow wetland (Sfw), and the aquatic plant pond (App) exhibited good removal effects on total phosphorus (TP) and NH3-N. In contrast, the removal effects on chemical oxygen demand (COD) and total nitrogen (TN) was unsatisfied. Various phosphorus removal bacteria were detected in the water samples from the Pep and the Sfw, such as Arthrobacter, Flavobacterium, and Planococcus. These findings indicated the water purification performance and the microbial community composition in an estuarine wetland buffer zone during a low-temperature period.

As a national key protection and restoration project, ecological restoration of Baiyangdian Wetland has an important significance for environmental management. As the research area in Zaozhadian wetland, the purification effect of warm season and cold season aquatic plants was studied under different overflying water qualities. It provides a theoretical and experimental basis for the ecological environment restoration and management of wetlands. The results showed that the warm season and cold season aquatic plants all played important roles on the nitrogen and phosphorus removal and maintained the stable water environmental from the nutrient release from soil. The warm season plant-mixed Myriophyllum spicatum and Ceratophyllum demersum and the cold season plant-Potamogeton crispus L. can be reasonably configurated for the wetland restoration.

Rumen liquid is excellent to effectively degrade lignocellulose. In this study, the suitable rice straw load during anaerobic fermentation of rice straw with rumen liquid as inoculum was explored to improve volatile fatty acid (VFA) production. At 10.0% rice straw load, the highest VFA concentration reached 10821.4 mg/L, and acetic acid and propionic acid were the main components. In 10.0% rice straw load system, high concentration of soluble chemical oxygen demand (SCOD) was also observed, and the enzymatic activities at 48 h were higher than those at other rice straw loads. At 10.0% rice straw load, lower diversity and richness of rumen bacteria were found than those at other rice straw loads. Bacteroides, Prevotella, and Ruminococcus were the main rumen bacteria during rice straw degradation, and the rumen bacteria might secret effective lignocellulolytic enzymes to enhance the hydrolysis and acidogenesis of rice straw. The determination of suitable rice straw load will be beneficial to the application of rumen liquid as inoculum in actual production.

This work studied the effect of total solid (TS) of sewage sludge on VFA production and composition in anaerobic fermentation. Results revealed that VFA concentration reached the highest of 10.16 g/L and the ratio of acetic acid, propionic acid and n-butyric acid was 5:2:2 with the 8% TS sewage sludge. In subsequent chain elongation with sludge fermentation liquid, n-caproic acid concentration reached 43.45 mmol/L. The microbial community analysis indicated that relative abundance of Clostridium_sensu_stricto_12 for n-caproic acid production was high (52.41%). The chain elongation with sludge fermentation liquid had more pathways to produce n-caproic acid, and the chain elongation reactions were thermodynamically possible. The mixed VFAs and high concentration of n-butyric acid benefitted n-caproic acid production. Carbon balance revealed that the VFA composition of sludge fermentation liquid was beneficial to the chain elongation. This study will contribute to wasted sludge minimization and high-value material production.

Rumen liquid can effectively degrade lignocellulosic biomass, in which rumen microorganisms play an important role. In this study, transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw was explored. Results showed that rice straw was efficiently hydrolyzed and acidified, and the degradation efficiency of cellulose, hemicellulose and lignin reached 46.2%, 60.4%, and 12.9%, respectively. The concentration of soluble chemical oxygen demand (SCOD) and total volatile fatty acid (VFA) reached 12.9 and 8.04 g L−1. The high-throughput sequencing results showed that structure of rumen bacterial community significantly changed in anaerobic digestion. The Shannon diversity index showed that rumen bacterial diversity decreased by 32.8% on the 5th day of anaerobic digestion. The relative abundance of Prevotella and Fibrobacter significantly increased, while Ruminococcus significantly decreased at the genus level. The Spearman correlation heatmap showed that pH and VFA were the critical factors affecting the rumen bacterial community structure. The function prediction found that rumen bacteria mainly functioned in carbohydrate transport and metabolism, which might contain a large number of lignocellulose degrading enzyme genes. These studies are conducive to the better application of rumen microorganisms in the degradation of lignocellulosic biomass.

Lignocellulosic biomass is one of the most abundant renewable resources, and their transformation into bioenergy is an effective approach to alleviate energy shortage and recycle organic wastes. This review summarized the rumen microorganisms and related enzymes, and rumen digestion strategies and mechanisms for improvement of anaerobic rumen digestion in engineering application. Main related literatures were searched on sciencedirect and web of science, systematically summarized, compared and analyzed. Rumen microorganisms accomplish the hydrolysis, acidogenisis and methanogenesis of lignocellulosic biomass, which mainly depends on the synergy of microorganisms and enzymes. Rumen bacteria are the main players and anaerobic fungi play an indispensable role in the hydrolysis and acidogenesis of lignocelluloses. The interaction of different microorganisms promotes the efficiency of lignocelluloses conversion to renewable energy in rumen digestion system, especially protozoa and methanogens. Rumen microorganisms secrete the cellulases, hemicellulases and ligninases, which have their own unique structure and action mode and synergistically promote the lignocellulose degradation. Anaerobic digestion reactor cannot be simply designed through simulating the rumen structure and environment, while the simulation of rumen digestion strategies according to the physicochemical properties and microbial community is more important. The substrate structure and additives significantly improve the rumen digestion of lignocellulosic biomass as a potential design strategy. Finally, the current challenges, future works, and prospects on biological conversion of lignocellulose to bioenergy with rumen microorganisms are outlined.

Properly increasing mobility of heavy metals could promote phytoremediation of contaminated soil. Fe1-xS/biochar was successfully prepared from sawdust with loading pyrrhotite (Fe1-xS) at a pyrolysis temperature of 550 °C. Thiobacillus were successfully adsorbed and enriched on the surface of Fe1-xS/biochar. Microbial growth for 36 d supported by bio-oxidization of Fe1-xS decreased the system pH from 4.32 to 3.50, increased the ORP from 298 to 487 mV, and the Fe3+ release reached 25.48 mg/g, enhancing the oxidation and leaching of soil Pb. Finally, Fe1-xS/biochar and Thiobacillus were simultaneously applied into Pb-contaminated soil for 60 d, the soil pH decreased from 7.83 to 6.72, and the exchangeable fraction of soil Pb increased from 22.86% to 37.19%. Ryegrass planting for 60 d in Pb-contaminated soil with Fe1-xS/biochar and Thiobacillus showed that the Pb content in shoot and root of ryegrass increased by 55.65% and 73.43%, respectively, confirming an obvious increase of phytoavailability of soil Pb. The relative abundance of Thiobacillus in remediated soil significantly increased from 0.06% to 34.55% due to the addition of Fe1-xS/biochar and Thiobacillus. This study provides a novel approach for regulating the Pb phytoavailability for phytoremediation of Pb-contaminated soil.

In-situ remediation of heavy metal-contaminated farmland mainly focuses on acidic soil, however, weak-alkaline farmland widely exists in north China. Meanwhile, fertilization is usually ignored, but it may influence remediation efficiency as well as grain production. In this paper, field experiments were carried out to investigate in-situ simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil by microbial agent mixed with fulvic acid (MFA), wheat straw biochar, sepiolite and their mixture. Results showed that addition of these conditioners decreased the soil available Cd by 39.86%–71.33% and the wheat Cd by 41.94%–87.10%. The decrease order of soil available Cd followed sepiolite > mixture > biochar > MFA, while the decrease order of wheat Cd was mixture > sepiolite > biochar > MFA. With addition of mixture, the wheat Cd reduced to 0.08 mg/kg, lower than the Cd limit of 0.1 mg/kg in Contaminant Limit in Food of National Food Safety Standards (GB2762-2017), and the highest wheat yield reached 7590 kg/hm2. The MFA had significant effects on improvement of soil organic matters, nutrients and rhizosphere microbes; the biochar was prominent in improving soil organic matters, inhibiting wheat Cd and soil available Cd; the sepiolite had obvious advantages in reducing wheat Cd and soil available Cd; and the mixture had a more balanced effect on soil remediation and fertilization. Correlation study showed that soil available Cd significantly affected the uptake of Cd by wheat, and wheat yield was significantly positively correlated with soil organic matters, available N. Therefore, reducing soil available Cd, increasing soil organic matters and nutrients are the keys to simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil for wheat production.

Using commercially available natural amino acids (L-Val, L-Leu, L-Phe) as chiral precursors, a series of N-substituted imidazole derivatives containing chiral groups was synthesized from the condensation reaction of amino acids, formaldehyde, glyoxal, and ammonia. Through esterification, reduction, chlorination, and subsequent substitution by thiols, chiral thioethers containing imidazole rings were synthesized, and the synthetic conditions were optimized. All the intermediates and the final products were characterized by NMR, ESI MS, HR MS, and IR.