HongYi Li

Insight into the effect of hydrogenation on efficiency of hydrothermal liquefaction and physico-chemical properties of biocrude oil.

Hydrothermal liquefaction of Nannochloropsis salina (N. salina) and larvae-vermicompost were conducted under both non-hydrogenating and hydrogenating subcritical conditions using H2 and Ni-Mo/Al2O3. Hydrogenation raised biocrude yields from 33.2% to 43.5% (vermicompost) and 55.6% to 78.5% (N. salina), whereas high heat values increased from 32.89 to 34.24 MJ/kg (vermicompost) and 36.30 to 37.53 MJ/kg (N. salina). Compared with the non-hydrogenated HTL process, the contents of acids, amides, phenols, and alcohols decreased, whereas hydrocarbons content increased. More branched cyclic nitrogenous compounds were detected in the hydrogenated biocrudes, whereas the aromatic/hetero-aromatic functionality was somewhat decreased. Smaller molecular weights and polydispersity index of the hydrogenated biocrudes were also detected. Results show that hydrogenation enhanced the removal of hydrophilic functional groups and the stabilization of radicals, thereby leading to the inhibition of loss of mass toward liquid and gaseous products and the upgrading of oil quality.

The antibiotic resistome of swine manure is significantly altered by association with the Musca domestica larvae gut microbiome

The overuse of antibiotics as veterinary feed additives is potentially contributing to a significant reservoir of antibiotic resistance in agricultural farmlands via the application of antibiotic-contaminated manure. Vermicomposting of swine manure using housefly larvae is a promising biotechnology for waste reduction and control of antibiotic pollution. To determine how vermicomposting influences antibiotic resistance traits in swine manure, we explored the resistome and associated bacterial community dynamics during larvae gut transit over 6 days of treatment. In total, 94 out of 158 antibiotic resistance genes (ARGs) were significantly attenuated (by 85%), while 23 were significantly enriched (3.9-fold) following vermicomposting. The manure-borne bacterial community showed a decrease in the relative abundance of Bacteroidetes, and an increase in Proteobacteria, specifically Ignatzschineria, following gut transit. ARG attenuation was significantly correlated with changes in microbial community succession, especially reduction in Clostridiales and Bacteroidales. Six genomes were assembled from the manure, vermicompost (final product) and gut samples, including Pseudomonas, Providencia, Enterococcus, Bacteroides and Alcanivorax. Transposon-linked ARGs were more abundant in gut-associated bacteria compared with those from manure and vermicompost. Further, ARG-transposon gene cassettes had a high degree of synteny between metagenomic assemblies from gut and vermicompost samples, highlighting the significant contribution of gut microbiota through horizontal gene transfer to the resistome of vermicompost. In conclusion, the larvae gut microbiome significantly influences manure-borne community succession and the antibiotic resistome during animal manure processing.

Attenuation of veterinary antibiotics in full-scale vermicomposting of swine manure via the housefly larvae ( Musca domestica )

Animal waste from concentrated swine farms is widely considered to be a source of environmental pollution, and the introduction of veterinary antibiotics in animal manure to ecosystems is rapidly becoming a major public health concern. A housefly larvae (Musca domestica) vermireactor has been increasingly adopted for swine manure value-added bioconversion and pollution control, but few studies have investigated its efficiency on antibiotic attenuation during manure vermicomposting. In this study we explored the capacity and related attenuation mechanisms of antibiotic degradation and its linkage with waste reduction by field sampling during a typical cycle (6 days) of full-scale larvae manure vermicomposting. Nine antibiotics were dramatically removed during the 6-day vermicomposting process, including tetracyclines, sulfonamides, and fluoroquinolones. Of these, oxytetracycline and ciprofloxacin exhibited the greater reduction rate of 23.8 and 32.9 mg m−2, respectively. Environmental temperature, pH, and total phosphorus were negatively linked to the level of residual antibiotics, while organic matter, total Kjeldahl nitrogen, microbial respiration intensity, and moisture exhibited a positive effect. Pyrosequencing data revealed that the dominant phyla related to Firmicutes, Bacteroidetes, and Proteobacteria accelerated manure biodegradation likely through enzyme catalytic reactions, which may enhance antibiotic attenuation during vermicomposting.

Redox potential and microbial functional gene diversity in wetland sediments under simulated warming conditions: implications for phosphorus mobilization

Microbial-driven biogeochemical cycles in wetlands impacted by global warming pose a potential downstream eutrophication risk. However, the consequences of ongoing warming on the functional and metabolic potential of sediment microbial communities are largely unknown. We incubated sediment samples under both ambient temperature conditions (control) and simulated warming conditions of 5°C above ambient temperature (warmed) using a novel field microcosm system. In warmed samples, we observed in situ a decreased thickness of the oxidized sediment layer and associated lower sediment redox potential. GeoChip 4.0, a comprehensive functional gene microarray, demonstrated that many functional genes that are involved in oxidation–reduction reactions and in phosphorus (P) degradation were preferentially enriched under warming conditions. The enriched genes included those genes encoding carbon monoxide dehydrogenase, acetyl-CoA carboxylase biotin carboxylase (ppc), and ribulose-1,5-bisphosphate carboxylase (Rubisco) for carbon fixation; nitrate reductases (narG) and nitrous oxide reductases (nosZ) for denitrification; cytochrome c for metal reduction; and exopolyphosphatase (ppx) for polyphosphate degradation. The redox potential was one of the most significant parameters linked to microbial functional gene structure. These results demonstrate that the enhanced hypoxia and anaerobic metabolic pathways accelerated sediment P mobilization in freshwater wetland subject to warming, raising the potential of water eutrophication.

Housefly Larva Vermicomposting Efficiently Attenuates Antibiotic Resistance Genes in Swine Manure, with Concomitant Bacterial Population Changes

ABSTRACT Manure from swine treated with antimicrobials as feed additives is a major source for the expansion of the antibiotic resistance gene (ARG) reservoir in the environment. Vermicomposting via housefly larvae (Musca domestica) can be efficiently used to treat manure and regenerate biofertilizer, but few studies have investigated its effect on ARG attenuation. Here, we tracked the abundances of 9 ARGs and the composition and structure of the bacterial communities in manure samples across 6 days of full-scale manure vermicomposting. On day 6, the abundances of genes encoding tetracycline resistance [tet(M), tet(O), tet(Q), and tet(W)] were reduced (P < 0.05), while those of genes encoding sulfonamide resistance (sul1 and sul2) were increased (P < 0.05) when normalized to 16S rRNA. The abundances of tetracycline resistance genes were correlated (P < 0.05) with the changing concentrations of tetracyclines in the manure. The overall diversity and richness of the bacteria significantly decreased during vermicomposting, accompanied by a 100 times increase in the relative abundance of Flavobacteriaceae spp. Variations in the abundances of ARGs were correlated with the changing microbial community structure and the relative abundances of the family Ruminococcaceae, class Bacilli, or phylum Proteobacteria. Vermicomposting, as a waste management practice, can reduce the overall abundance of ARGs. More research is warranted to assess the use of this waste management practice as a measure to attenuate the dissemination of antimicrobial residues and ARGs from livestock production before vermicompost can be safely used as biofertilizer in agroecosystems.

Enantiomer signature and carbon isotope evidence for the migration and transformation of DDTs in arable soils across China

Due to the adverse impact of DDTs on ecosystems and humans, a full fate assessment deems a comprehensive study on their occurrence in soils over a large region. Through a sampling campaign across China, we measured the concentrations, enantiomeric fractions (EFs), compound-specific carbon isotope composition of DDT and its metabolites, and the microbial community in related arable soils. The geographically total DDT concentrations are higher in eastern than western China. The EFs and δ13C of o,p’-DDT in soils from western China show smaller deviations from those of racemic/standard compound, indicating the DDT residues there mainly result from atmospheric transport. However, the sources of DDT in eastern China are mainly from historic application of technical DDTs and dicofol. The inverse dependence of o,p’-DDT and p,p’-DDE on temperature evidences the transformation of parent DDT to its metabolites. Initial usage, abiotic parameters and microbial communities are found to be the main factors influencing the migration and transformation of DDT isomers and their metabolites in soils. In addition, a prediction equation of DDT concentrations in soils based on stepwise multiple regression analysis is developed. Results from this study offer insights into the migration and transformation pathways of DDTs in Chinese arable soils, which will allow data-based risk assessment on their use.

Linking Stoichiometric Homeostasis of Microorganisms with Soil Phosphorus Dynamics in Wetlands Subjected to Microcosm Warming

Soil biogeochemical processes and the ecological stability of wetland ecosystems under global warming scenarios have gained increasing attention worldwide. Changes in the capacity of microorganisms to maintain stoichiometric homeostasis, or relatively stable internal concentrations of elements, may serve as an indicator of alterations to soil biogeochemical processes and their associated ecological feedbacks. In this study, an outdoor computerized microcosm was set up to simulate a warmed (+5°C) climate scenario, using novel, minute-scale temperature manipulation technology. The principle of stoichiometric homeostasis was adopted to illustrate phosphorus (P) biogeochemical cycling coupled with carbon (C) dynamics within the soil-microorganism complex. We hypothesized that enhancing the flux of P from soil to water under warming scenarios is tightly coupled with a decrease in homeostatic regulation ability in wetland ecosystems. Results indicate that experimental warming impaired the ability of stoichiometric homeostasis (H) to regulate biogeochemical processes, enhancing the ecological role of wetland soil as an ecological source for both P and C. The potential P flux from soil to water ranged from 0.11 to 34.51 mg m−2 d−1 in the control and 0.07 to 61.26 mg m−2 d−1 in the warmed treatment. The synergistic function of C-P acquisition is an important mechanism underlying C∶P stoichiometric balance for soil microorganisms under warming. For both treatment groups, strongly significant (p<0.001) relationships fitting a negative allometric power model with a fractional exponent were found between n-HC∶P (the specialized homeostatic regulation ability as a ratio of soil highly labile organic carbon to dissolved reactive phosphorus in porewater) and potential P flux. Although many factors may affect soil P dynamics, the n-HC∶P term fundamentally reflects the stoichiometric balance or interactions between the energy landscape (i.e., C) and flow of resources (e.g., N and P), and can be a useful ecological tool for assessing potential P flux in ecosystems.

Decomposition and humification of dissolved organic matter in swine manure during housefly larvae composting

Housefly larvae (Musca domestica) composting has been increasingly adopted as an efficient practice to achieve value-added swine manure bioconversion, but few researches have evaluated the features of compost maturity by examining the biochemical compositions of dissolved organic matter (DOM) in compost. Here, we adopted spectrum fingerprint technologies to explore the related transformation mechanisms of DOM in compost by conducting field investigations in a full-scale housefly larvae composting farm. The 1-week composting with larvae significantly decreased DOM concentrations from 192.9 to 77.1 g kg−1. The hydrolysis of proteins and lipids were enhanced during composting, as well as a build-up of aromatic substances, while contents of fulvic- and humic-like substances were augmented on Day 5 and Day 6 (ranged from 0.04 to 0.65 and 0.11 to 0.59 for Fmax, respectively). Compared with traditional composting without the aid of larvae, the stronger biodegradation of DOM and the subsequent formation of humus in compost, led to a higher level of aromaticity and humification under housefly larvae bioconversion, generating a more stable bio-product for downstream utilisation.

Dynamic formation of zeolite synthesized from fly ash by alkaline hydrothermal conversion

This study was designed to characterize the dynamic formation of zeolite synthesized from fly ash (ZFA) and to identify the zeolitization mechanisms during a 160-h-long hydrothermal alkaline conversion at 95°C by using fly ash (FA) samples collected from four typical thermoelectric power plants in China, with the purpose of improving ZFA quality. The process of synthesizing ZFA can be fundamentally divided into five stages: induction stage (0–0.5 h), accelerating dissolution stage (0.5–12 h), nucleation and/or crystallization stage (12–24 h), crystal growth stage (24–72 h) and crystal transformation stage (72–160 h). The crystal growth stage determined the quality of zeolite crystallization, coupled with functions of re-assembling the silicon–aluminium tetrahedral network and developing submicro- and/or nanometer microstructure. A 48-h-long hydrothermal conversion generated ZFAs that had a greater specific surface area (26.0–89.4 times) and cation exchange capacity (29.6–71.0 times) than FA, which successfully sequestrated 41–95% of ammonium and 75–98% of phosphate from swine manure. However, over-reaction resulted in more stable hydroxysodalite and/or sodalite, surface agglomeration and cracking, and energy wasting. This work suggests that the reuse of recycled synthesis materials should occur during the fourth step (24–72 h).

The chemodiversity of paddy soil dissolved organic matter correlates with microbial community at continental scales

BackgroundPaddy soil dissolved organic matter (DOM) represents a major hotspot for soil biogeochemistry, yet we know little about its chemodiversity let alone the microbial community that shapes it. Here, we leveraged ultrahigh-resolution mass spectrometry, amplicon, and metagenomic sequencing to characterize the molecular distribution of DOM and the taxonomic and functional microbial diversity in paddy soils across China. We hypothesized that variances in microbial community significantly associate with changes in soil DOM molecular composition.ResultsWe report that both microbial and DOM profiles revealed geographic patterns that were associated with variation in mean monthly precipitation, mean annual temperature, and pH. DOM molecular diversity was significantly correlated with microbial taxonomic diversity. An increase in DOM molecules categorized as peptides, carbohydrates, and unsaturated aliphatics, and a decrease in those belonging to polyphenolics and polycyclic aromatics, significantly correlated with proportional changes in some of the microbial taxa, such as Syntrophobacterales, Thermoleophilia, Geobacter, Spirochaeta, Gaiella, and Defluviicoccus. DOM composition was also associated with the relative abundances of the microbial metabolic pathways, such as anaerobic carbon fixation, glycolysis, lignolysis, fermentation, and methanogenesis.ConclusionsOur study demonstrates the continental-scale distribution of DOM is significantly correlated with the taxonomic profile and metabolic potential of the rice paddy microbiome. Abiotic factors that have a distinct effect on community structure can also influence the chemodiversity of DOM and vice versa. Deciphering these associations and the underlying mechanisms can precipitate understanding of the complex ecology of paddy soils, as well as help assess the effects of human activities on biogeochemistry and greenhouse gas emissions in paddy soils.