Microbial Community Changes During the Composting of Municipal Solid Waste

Abstract Phospholipid fatty acid (PLFA) analysis has been used to characterize microorganisms from a range of different environments, but has not been previously used in the assessment of compost organisms. Compost processing and maturity are assumed to be related to the microorganisms present, but methods to elucidate and evaluate these relationships are lacking. In this study, PLFA analysis was used to follow microbial community changes during the composting of municipal solid waste (MSW). Patterns of change were compared between pilot- and full-scale facilities and between varied feedstocks. At the pilot level, actual MSW and two synthetic MSW formulations (similar C:N, different available C) were composted. At the full-scale facilities, actual MSW was composted as was actual MSW amended with nitrogen. The PLFA data generated by all studies was analyzed using principal component and multivariate statistical methods. The PLFA profiles changed over the composting process in a consistent and predictable manner. PLFA profiles also proved to be characteristic of specific stages of composting and may, therefore, be useful in evaluating (and optimizing) the progress of material processing and product maturity. Received: 28 November 1995; Revised: 12 March 1996; Accepted: 15 March 1996     

Growth of Sclerotiumrolfsiiat Different Concentration of Oxygen and Carbon Dioxide

Sclerotium rolfsii was grown in various atmospheres, the compositionsof which were controlled by the diffusion column technique.Growth-rate of mycelium was constant within a range of oxygenconcentrations from 3 to 21 per cent, but dirminished steadilyas carbon dioxide concentration increased from about 0.03 percent. The rate of sclerotial germination was reduced by oxygenconcentrations less than 6 per cent and by carbon dioxide concentrationsgreater than about 10 per cent. No sclerotia were formed ifthe concentration of oxygen fell below 15 per cent or if thatof carbon dioxide exceeded 4 per cent. The effects of inverserationof gases, from 0 per cent oxygen: 20 per cent carbon dioxideto 21 per cent oxygen: 0 per cent carbon dioxide, were in eachcase similar to the effect of the corresponding carbon dioxideconcentration when combined with 21 per cent oxygen.     

Effects of Continuous Thermophilic Composting (CTC) on Bacterial Community in the Active Composting Process

The method of continuous thermophilic composting (CTC) remarkably shortened the active composting cycle and enhanced the compost stability. Effects of CTC on the quantities of bacteria, with a comparison to the traditional composting (TC) method, were explored by plate count with incubation at 30, 40 and 50°C, respectively, and by quantitative PCR targeting the universal bacterial 16S rRNA genes and the Bacillus 16S rRNA genes. The comparison of cultivatable or uncultivatable bacterial numbers indicated that CTC might have increased the biomass of bacteria, especially Bacillus spp., during the composting. Denaturing gradient gel electrophoresis (DGGE) analysis was employed to investigate the effects of CTC on bacterial diversity, and a community dominated by fewer species was detected in a typical CTC run. The analysis of sequence and phylogeny based on DGGE indicated that the continuously high temperature had changed the structure of bacterial community and strengthened the mainstay role of the thermophilic and spore-forming Bacillus spp. in CTC run.     

Population Changes in Enteric Bacteria and Other Microorganisms During Aerobic Thermophilic Windrow Composting

Composting of wastes from swine feeding operations was studied. The effects of the frequency of turning the wastes and addition of straw to improve the physical structure were studied to determine the most effective technique to rapidly increase the temperature and, consequently, destroy coliforms and Salmonella. Four different treatments were studied; the results showed that, with addition of 5% (wt/wt) straw and mechanical turning of the compost 20 times per week, the temperature reached 60 C within 3 days and enteric bacteria were destroyed within 14 days.     

复合微生物菌剂在剩余污泥堆肥中的作用研究

应用复合微生物菌剂对剩余污泥进行堆肥试验,较系统地研究了复合微生物菌剂在剩余污泥堆肥系统中的作用。结果表明:接种复合微生物菌剂进行剩余污泥堆肥,与对照组相比,不但能够提高堆肥温度,而且高温持续时间长,堆肥反应速率加快,腐熟时间缩短,当接种量为7%(体积比)时,腐熟时间比对照组提前了12 d。     

Growth Response to Salinity at High Levels of Carbon Dioxide

Plants of the C₃ species Phaseolus vulgaris and Xanthium strumariumand of the C₄ salt-sensitive Zea mays and the C₄ halophyte Atriplexhalimus were grown with and without NaCl salt-stress at normal(340 µl I^–1) and at high (2500 µl I^–1)ambient CO₂. In all four species growth (dry weight increment)was enhanced by CO₂ supplementation. The relative response wasgreater in the salinized than in the control plants. Plant topsresponded more to CO, than the roots. CO₂ supplementation appearsto increase plant tolerance of low levels of salinity. Key words: Salinity, CO₂, Growth     

Spore Germination and Mycelial Growth of Streptomycetes at Different Humidity Levels

This study is the first to show the ability of streptomycetes to develop at a very low humidity level. All of the streptomycetes studied produced growth at low humidity (a_w 0.86 and 0.67). This capacity was most markedly pronounced in Streptomyces odorifer, whose spores were capable of germinating, and mycelial germs increased in length, at the air humidity a_w 0.50. The formation of lateral branches (mycelium branching) at this humidity was noted only in single S. odorifer germs and only after 72 h of incubation. Study of streptomycete growth on an agarized medium with different osmotic pressures, created by various glycerol concentrations in the medium, showed that, at a_w 0.67, the spores of all the streptomycetes studied germinate, producing mycelial germs but not microcolonies. The ecological significance of mycelial prokaryotes in soil microbial communities that develop and function under conditions of extremely low humidity is discussed.     

Effects of Elevated Tetracycline Concentrations on Aerobic Composting of Human Feces: Composting Behavior and Microbial Community Succession

The effects of antibiotics on aerobic composting are investigated by dosing of tetracycline (TC) in fresh human feces with sawdust as biomass carrier. Variability in process parameters such as temperature, pH, water-soluble carbon, germination index (GI) and dehydrogenase activity (DHA) are evaluated at TC dosages of 0, 100, 250 and 500 mg/kg in a 21-day composting. Moreover, microbial community succession is examined by high-throughput 16S rRNA gene sequencing. Findings indicate significant impacts to the process parameters with the increase of TC concentration such as inhibition of temperature increases during aerobic composting, lowering of pH, increasing of water-soluble carbon residue, a decrease of GI, and hindering of DHA. Furthermore, elevated TC concentrations significantly alter the microbial community succession and reduce the community diversity and abundance. Therefore, interference in microbial community structures and a hindrance to biological activity are believed to be the main adverse effects of TC on the composting process and maturity of the composting products.     

Grain Size and Seedling Growth of Wheat at Different Ploidy Levels

A study was made of the influence of grain size variation withinand between diploid, tetraploid and hexaploid wheat, on a numberof seedling growth characters. Differences in grain size within the three ploidy levels appearedto be related to total photosynthetic area and dry weight accretionin the seedling. In the diploids there was a positive correlationbetween seed size and total photosynthetic area (r = +0·99,P < 0·01) and total dry weight (r = +0·84,P < 0·05) of the seedling at 10 weeks after emergence.In the tetraploid and hexaploids, seed size was negatively correlatedwith both total photosynthetic area (r = –0·69,P < 0·05 and r = –0·33, P < 0·05for the tetraploids and hexaploids respectively) and total dryweight (r = –0·69, P < 0·05 and r = –0·59,P < 0·05 for the tetraploids and hexaploids respectively),of the seedlings 10 weeks after emergence. The main physiological distinction between the tetraploids andhexaploids appeared to be the superiority of the hexaploidsin rate of leaf appearance and the lower ratio of expanded tounexpanded leaves in the seedling 10 weeks after emergence.The tetraploids, in turn, appeared to be superior to the diploidsin these two characters. Triticum spp., wheat, polyploidy, grain size, photosynthetic area, net assimilation rate, tiller number     

The Hemoglobin Conformation in Erythrocytes at Different Levels of Oxygen Partial Pressure

Biophysics - The variation in the conformations of hemoglobin heme and globin in response to different oxygen partial pressures (pO2) has been studied by Raman spectroscopy inside erythrocytes and...     

城市生活垃圾堆肥发酵中微生物菌群变化规律的研究

通过对垃圾处理厂静态堆肥不同区域的微生物菌群与数量的分析,表明了城市生活垃圾堆肥发酵中微生物菌群的变化规律,温度与微生物菌群的相关性,指出了高温微生物菌群数量影响堆肥的效率。建议在静态一次堆肥发酵周期中,增加通气量和翻堆频率,有利于增强微生物菌群的活力和提高堆肥质量。     

Change in Microbial Numbers during Thermophilic Composting of Sewage Sludge with Reference to CO2 Evolution Rate

Dewatered sewage sludge was composted in a laboratory-scale autothermal reactor in which a constant temperature of 60°C was kept as long as possible by regulating the air feed rate. The change in CO₂ evolution rate was measured continuously from the start up through the cessation of compositing. The succession of mesophilic bacteria, thermophilic bacteria, and thermophilic actinomycetes was also observed during the composting. Specific CO₂ evolution rates of thermophilic bacteria and actinomycetes in the constant-temperature region of 60°C were assessed quantitatively. It was found that the CO₂ evolution rate was attributed to thermophilic bacteria at the initial stage of 60°C and to thermophilic actinomycetes at the later stage of 60°C.     

Analysis of Factors Affecting the Accuracy, Reproducibility, and Interpretation of Microbial Community Carbon Source Utilization Patterns

We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microtiter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal-components analysis (PCA), and model communities with different compositions were clearly separated on the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.     

Use of Phospholipid Fatty Acids and Carbon Source Utilization Patterns To Track Microbial Community Succession in Developing Compost

Carbon source utilization and phospholipid fatty acid analyses were used to track the rapidly changing microbial community in composting dairy waste. Microbial abilities to utilize common plant sugars increased during composting. Community phospholipid profiles changed significantly over time. Phospholipids suggested the presence of more thermophiles and fewer bacteria with continued compost development.     

Microbial Community Structure at Different Fermentation Stages of Kutajarista, a Herbal Formulation

Kutajarista is an Ayurvedic fermented herbal formulation prescribed for gastrointestinal disorders. This herbal formulation undergoes a gradual fermentative process and takes around 2 months for production. In this study, microbial composition at initial stages of fermentation of Kutajarista was assessed by culture independent 16S rRNA gene clone library approach. Physicochemical changes were also compared at these stages of fermentation. High performance liquid chromatography–mass spectrometry analysis showed that Gallic acid, Ellagic acid, and its derivatives were the major chemical constituents recovered in this process. At 0 day of fermentation, Lactobacillus sp., Acinetobacter sp., Alcaligenes sp., and Methylobacterium sp. were recovered, but were not detected at 8 day of fermentation. Initially, microbial diversity increased after 8 days of fermentation with 11 operational taxonomic units (OTUs), which further decreased to 3 OTUs at 30 day of fermentation. Aeromonas sp., Pseudomonas sp., and Klebsiella sp. dominated till 30 day of fermentation. Predominance of γ- Proteobacteria and presence of gallolyl derivatives at the saturation stage of fermentation implies tannin degrading potential of these microbes. This is the first study to highlight the microbial role in an Ayurvedic herbal product fermentation.     

Change in Microbial Numbers during Thermophilic Composting of Sewage Sludge with Reference to CO(2) Evolution Rate

Dewatered sewage sludge was composted in a laboratory-scale autothermal reactor in which a constant temperature of 60 degrees C was kept as long as possible by regulating the air feed rate. The change in CO(2) evolution rate was measured continuously from the start up through the cessation of compositing. The succession of mesophilic bacteria, thermophilic bacteria, and thermophilic actinomycetes was also observed during the composting. Specific CO(2) evolution rates of thermophilic bacteria and actinomycetes in the constant-temperature region of 60 degrees C were assessed quantitatively. It was found that the CO(2) evolution rate was attributed to thermophilic bacteria at the initial stage of 60 degrees C and to thermophilic actinomycetes at the later stage of 60 degrees C.     

Microbial Community Structure at Different Depths in Disturbed and Undisturbed Semiarid Mediterranean Forest Soils

Metabolic abilities and micrfiobial community structure were investigated through three semiarid Mediterranean soils of SE Spain. The soils were (1) a Typic Calcixerept under an adult pine plantation (PP), growing on abandoned agricultural terraces; (2) a Typic Calcixeroll under a native pinewood (NP); and (3) a Typic Haploxerept covered with a grass steppe (GS). PP and NP were similar as regards their genesis, but the former used to be tilled. NP and GS were undisturbed and supported natural and seminatural vegetation, respectively. Seven samples in 10-cm depth increments were taken in triplicate along each soil profile. Community-level physiological profiles based on sole-C-source use were determined to characterize the metabolic abilities. A 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis analysis was performed to investigate the microbial genetic structure. Plant cover and land-use history were major determinants of microbial community structure. Microbial communities residing in soils under a native pinewood, the most diverse and stable plant cover, were the most complex both metabolically and genetically. The microbial community structure distinctly changed with depth, related to the quantity and quality of total organic carbon. Both undisturbed soils showed falling gradients of metabolic and genetic complexity, which were invariably of a greater magnitude in the mature woodland than in the grass steppe. In the planted pinewood, however, the substrate-use diversity increased with depth, apparently a response to the depleted metabolic abilities within its upper layer (0–30 cm). Tilling and plant cover removal might be responsible for such a perturbation. In the same profile, molecular fingerprint patterns of the topsoil layer (0–10 cm) indicated a disturbed genetic structure that might underlie the loss of metabolic abilities. However, the genetic structure of the deeper layers of the planted and native pinewoods was not dissimilar, revealing that equivalent genetic resources perform different environmental functions under changing soil scenarios.     

Growth of Plants in Different Oxygen Concentrations

Dwarf french beans (Phaseolus vulgaris var. Canadian Wonder)were grown in chambers at 25?C with the roots aerated at 20per cent oxygen and tops variously maintained at: T₁ O₂ 0.21;CO₂ 270?10^–6: T₂; O₂ 0.05, CO₂, CO₂ 270?10^–6: T₃;O₂ 0.21; CO₂ 550?10^–6. Experiment 1 (T₁ and T₂) lasted2 weeks: Experiment 2 (T₁ T₂ and T₃) only one week. Hourly estimatesof CO₂ uptake were made by gas analysis and weekly estimatesof fresh weight, dry matter in tops and roots, and leaf area,by sampling. Light intensity was 80 W m^–2 of photosyntheticallyactive radiation. An attempt was made to explain the results in terms of a simplelight absorption model such that where dV/dt is the rate of CO₂ uptake per plant, ßis the photosynthetic efficiency, I₀ is the incident light intensity,f is the fraction of incident light absorbed by unit leaf layerand L is the leaf area index. The analysis showed that ß(T₂)was at least double ß(T₁), whilst f(T₂) was smallerthan f(T₁) at a given leaf area. The results also required thatthroughout the period of the experiment, fL(T₁)=fL(T₂) at anygiven time, i.e. the treatment with the larger leaf area (T₂)has the smaller value of f, and therefore intercepts less lightper unit leaf area. This could be advantageous for plant growth,but requires further experiments. The photosynthetic rates per unit leaf are about 40 per centgreater in T₂ than T₁. Over the relatively short period of the experiment the resultsare adequately described by U=btⁿ, where U is the accumulatedcarbon dioxide uptake, b is related to the photosynthetic efficiency(different for the differing treatments), and n is a constant(similar for all treatments). This relationship with time isbelieved to be a relationship with accumulated radiation, forthe light was constant throughout the experiments. Comparisons of carbon fixed (measured gas uptake) and dry matteraccumulation (sampling) show great scatter with an average valueof 0.43. The first week's results were generally smaller thanthis value and the second week's greater. Energy fixation as a fraction of photosynthetically active radiationon the ground area covered by the plants ranged from 3.5 to10 per cent. The results from treatment T₃ were similar to T₂ suggestingthat increasing CO₂ concentration decreases the growth inhibitionat 21 per cent O₂.     

Establishment and Early Growth of Willow at Different Levels of Weed Competition and Nitrogen Fertilization

To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora (Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30 days after willow planting. The buckets were fertilized with 30 or 90 kg N ha^?1. Willow with weeds sown after 15 days produced less biomass and smaller leaf area and had a lower maximum shoot height compared to willow planted without weeds and willow with weeds sown after 26 or 30 days. Fertilization with 90 kg N ha^?1 gave higher willow biomass production in willow with weeds sown after 26 or 30 days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed biomass when planted without willows and in the willow-weed mixture with weeds sown after 15 days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation, fertilization should be delayed.