Sulfate reduction at pH 4.0 for treatment of process and wastewaters

Acidic industrial process and wastewaters often contain high sulfate and metal concentrations and their direct biological treatment is thus far not possible as biological processes at pH < 5 have been neglected. Sulfate‐reducing bacteria convert sulfate to sulfide that can subsequently be used to recover metals as metal‐sulfides precipitate. This study reports on high‐rate sulfate reduction with a mixed microbial community at pH 4.0 and 4.5 with hydrogen and/or formate as electron donors. The maximum sulfate reducing activity at pH 4.0 was sustained for over 40 days with a specific activity 500‐fold greater than previously reported values: 151 mmol sulfate reduced/L reactor liquid per day with a maximum specific activity of 84 mmol sulfate per gram of volatile suspended solids per day. The biomass yield gradually decreased from 38 to 0.4 g volatile suspended solids per kilogram of sulfate when decreasing the reactor pH from pH 6 to 4. The microorganisms had a high maintenance requirement probably due maintaining pH homeostasis and the toxicity of sulfide at low pH. The microbial community diversity in the pH 4.0 membrane bioreactor decreased over time, while the diversity of the sulfate reducing community increased. Thus, a specialized microbial community containing a lower proportion of microorganisms capable of activity at pH 4 developed in the reactor compared with those present at the start of the experiment. The 16S rRNA genes identified from the pH 4.0 grown mixed culture were most similar to those of Desulfovibrio species and Desulfosporosinus sp. M1. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

生物竞争排斥对油藏微生物群落结构变化影响

【目的】海上S油田采用生物竞争排斥技术治理油藏硫化氢产出取得一定成效,本研究通过揭示该技术对油藏环境中微生物群落结构的影响,尝试研究硫化氢治理过程中产生效果差异的因素。【方法】采用高通量测序分析等方法对加入硝酸盐、亚硝酸盐等药剂后,治理效果低效井、高效井及未治理井中不同微生物群落结构变化进行分析。【结果】与低效井和未治理井相比,高效井中的反硝化菌和石油降解菌种类和丰度明显增加,其中石油降解菌增加24.14%,反硝化细菌增加5.23%;Fe²⁺、Zn²⁺等离子的存在对不同井间治理效果差异和微生物群落变化具有一定影响。【结论】海上油田硫化氢治理中,生物竞争排斥技术不仅可以明显降低硫化氢产出,同时对油藏微生物群落环境也影响显著,微生物群落结构分析可作为硫化氢治理效果评价的重要指标,为海上油田硫化氢治理工作提供技术支持。     

Regime shift and robustness of organism-created environments: A model for microbial ecosystems

Organism-environment interactions are different from organism-resource interactions in two respects: (1) resources can only be consumed by organisms whereas environmental conditions can be increased or decreased depending on the species; (2) high resource conditions generally stimulate the growth of organisms, whereas extreme environmental conditions are not necessarily favored because each species usually has an optimum range for growth. To investigate the properties of an organism-environment feedback system, we analyze a model for microbial ecosystems in which a single microorganism species can modify the environmental pH. We demonstrate that the equilibrium level of the environmental pH can be partially regulated at a relatively constant value even if the pH in the influx to the ecosystem changes over a wide range. For species that acidify the medium, the equilibrium pH is somewhat lower than the pH optimal for the species. The pH-stabilizing effect of microorganisms is stronger if their growth is self-limited by the environmental pH. When the influx becomes sufficiently alkaline, the population of the organism suddenly disappears and the environmental pH changes abruptly. The system shows bi-stability and hysteresis and therefore differs from a standard resource competition model composed of a single species that consumes resources.     

Diversity of the communities of acidophilic chemolithotrophic microorganisms in natural and technogenic ecosystems

The main representatives of acidophilic chemolithotrophs oxidizing sulfide minerals, ferrous iron, elemental sulfur, and reduced sulfur compounds and forming microbial communities in the natural and technogenic ecosystems with low pH values and high concentrations of heavy metal ions are listed. The species and strain diversity of the communities and environmental factors affecting their composition (temperature, pH value, energy substrate, mineralogical composition of sulfide ore concentrates, the presence of organic substances, and level of aeration) are analyzed. Involvement of mobile genetic elements (IS elements and plasmids) in the structural changes of the chromosomal DNA in the course of switching microbial metabolism to the oxidation of new energy substrates or under increased concentrations of metal ions is shown to be a probable mechanism responsible for the intraspecific genetic heterogeneity of the populations. Importance of determination of the dominant strains of different microbial species in the communities and of their physiological peculiarities for stabilization, optimization, and enhancement of efficiency of biotechnological processes for sulfide mineral oxidation is stressed.     

Effects of acidic water on young-of-the-year smallmouth bass (Micropterus dolomieui)

Synopsis Smallmouth bass (Micropterus dolomieui) populations are declining in areas vulnerable to anthropogenic acidification. To determine if populations may be lost directly from acid effects (i.e., in isolation from synergists), we performed a laboratory study on the effects of acid exposure on growth, survival and histology of young smallmouth bass (3 to 36 d post swimup). We exposed them to declining, then fluctuating acid levels averaging pH 7.4 (control), 5.7 and 5.0. Substantial decreases in survival were observed, as well as damage to tissues. Survival declined with increasing acidity to 43% of that in controls at pH 5.7 and to 4% at pH 5.0. Histological analysis revealed severe changes in the most acidic treatment, with damage to blood, gill, and epithelial tissue. In contrast, growth was less useful as an indicator of response to acidity. Growth in both length and dry weight was greater at the lower pH levels than in controls. This was probably a reflection of lower survival at the lower pH levels, reduced density, and hence less competition for food. Our results suggest that an increase in environmental acidity is sufficient to cause losses in this species, even in the absence of synergists such as heavy metals.School of Forest Resources, University of Georgia, Athens, GA 30602, U.S.A.     

Kinetics of substrate inhibition of exponential yeast growth

This work concerns mathematical modeling of the rate of microbial growth on inhibitory levels of nutrients as affected by pH, concentration of the nutrients, temperature, cultivation method, and method of data analysis. Candida utilis (ATCC 9226) was grown with sodium acetate as growth-limiting carbon and energy source in mineral salts medium in shake flask and continuous cultures to study inhibition by excess acetate. Differential shake flask cultures were grown at low yeast concentrations at temperatures (T) of 25 and 30°C, pH's between 5.5 and 7.0, and acetate concentrations (S) between 0.25 and 3.0% (w/v). Growth data were exponential with correlation coefficients greater than 0.995 in 49 of 56 experiments; the lowest correlation coefficient was 0.986. Specific growth rates (μ) determined by graphical methods showed only fair correlation with those determined by regression analysis. Both sets of specific growth rate data were grouped at constant T and pH and fitted to the three parameter equation, The improvement in use of the fitted equation instead of the mean value was significant with greater than 70% confidence in all (14 groups) and 90% confidence in only half of the data groups; the correlation does not improve with the increasing acetate inhibition at lower pH. Both defects in the model and insufficient data at each pH are responsible. A modified six parameters with hydrogen ion concentration(H⁺) as follows: Specific growth rates calculated with the six parameter equation matched observed values in all groups of isothermal data better than the means with greater than 99% confidence. The six parameter model adequately represents effects of acetate and hydrogen ion concentrations under constant or slowly changing environmental conditions and balanced growth; although better models probably exist. Thus steady-stste and transient continuous culture experiments agreed with many published growth yields, but specific growth rates could only be predicted qualitatively from the model fit to the shake flask data. The data and present models could be incorporated into published models for transient growth at low nutrient concentrations to correlate and perhaps predict microbial growth kinetics over a much wider range of growth conditions than now possible.     

蛋白质过硫化修饰研究进展

过硫化修饰在保护蛋白质的正常功能和信号传递过程中起着重要作用,对维持细胞的正常生理代谢平衡、保护细胞抵抗氧化应激及硫稳态调控等方面具有重要影响。本文综述了硫化氢、活性硫及半胱氨酸代谢的内在关联以及硫稳态调控,阐述了蛋白质过硫化修饰的机制及在微生物硫稳态调节中的作用,对未来的研究方向和趋势提供了新的思路。     

Microbial community structure and sulfur biogeochemistry in mildly‐acidic sulfidic geothermal springs in Yellowstone National Park

Geothermal and hydrothermal waters often contain high concentrations of dissolved sulfide, which reacts with oxygen (abiotically or biotically) to yield elemental sulfur and other sulfur species that may support microbial metabolism. The primary goal of this study was to elucidate predominant biogeochemical processes important in sulfur biogeochemistry by identifying predominant sulfur species and describing microbial community structure within high‐temperature, hypoxic, sulfur sediments ranging in pH from 4.2 to 6.1. Detailed analysis of aqueous species and solid phases present in hypoxic sulfur sediments revealed unique habitats containing high concentrations of dissolved sulfide, thiosulfate, and arsenite, as well as rhombohedral and spherical elemental sulfur and/or sulfide phases such as orpiment, stibnite, and pyrite, as well as alunite and quartz. Results from 16S rRNA gene sequencing show that these sediments are dominated by Crenarchaeota of the orders Desulfurococcales and Thermoproteales. Numerous cultivated representatives of these lineages, as well as the Thermoproteales strain (WP30) isolated in this study, require complex sources of carbon and respire elemental sulfur. We describe a new archaeal isolate (strain WP30) belonging to the order Thermoproteales (phylum Crenarchaeota, 98% identity to Pyrobaculum/Thermoproteus spp. 16S rRNA genes), which was obtained from sulfur sediments using in situ geochemical composition to design cultivation medium. This isolate produces sulfide during growth, which further promotes the formation of sulfide phases including orpiment, stibnite, or pyrite, depending on solution conditions. Geochemical, molecular, and physiological data were integrated to suggest primary factors controlling microbial community structure and function in high‐temperature sulfur sediments.     

Effect of hydrogen sulfide on growth of sulfate reducing bacteria

A culture of sulfate reducing bacteria (SRB) growing on lactate and sulfate was incubated at different pH values in the range of 5.8-7.0. The effect of pH on growth rate was determined in this pH range; the highest growth rate was observed at pH 6.7. Hydrogen sulfide produced from sulfate reduction was found to have a direct and reversible toxicity effect on the SRB. A hydrogen sulfide Concentration of 547 mg/L (16.1 mM) completely inhibited the culture growth. Comparison between acetic acid and hydrogen sulfide inhibition is presented and the concomitant inhibition kinetics are mathematically described. (c) 1992 John Wiley & Sons, Inc.     

除臭微生物的筛选复配及其在堆肥中的应用

【目的】从沼渣和硫铁矿场土壤中分离可以去除氨氮和硫化物的微生物,并筛选复配后应用于堆肥中,以减少畜牧业粪便处理时臭气的释放量,改善工作环境。【方法】利用选择培养基分别筛选除氨和除硫的微生物,并进行16SrRNA基因序列分析鉴定,挑选效果较好的菌株进行组合,复配出微生物除臭剂将其应用于粪便堆肥中,通过检测现场氨气和硫化氢浓度初步评估其除臭效果。【结果】分离出了12株除氨微生物和5株除硫微生物,挑选出5株效果较好的菌株分别标记为N-2、N-5、N-6、N-11和S-3。复配实验表明菌株N-5+N-6+N-11+S-3组成的微生物除臭剂效果最佳,对NH4+-N和S2–去除率最高,分别为82.46%和84.84%。同时,堆肥应用实验证明微生物除臭剂具有除臭功效,尤其是在堆肥前期,在第7天翻堆的过程中氨气和硫化氢释放量相对于对照组减少了62.84%和53.12%。堆肥结束,与对照组相比,微生物除臭剂组氨氮含量低于对照组33.62%。【结论】本研究获得的微生物除臭剂有效降低了畜禽粪便堆肥过程中恶臭气体的释放,在改善畜牧业粪便堆肥处理环境方面具有较大的应用潜力。     

Influence of environmental variability on the growth of Lilac-crowned Parrot nestlings

Growth rate parameters were analysed for Lilac-crowned Parrot Amazona finschi nestlings in the tropical dry forest of the Reserva de la Biosfera Chamela-Cuixmala, Mexico. Growth rates for psittacine species follow the inverse relation with body mass observed for neotropical landbirds, with larger parrot species exhibiting slower growth rates. There was significant variation between years in size and growth rates of Lilac-crowned Parrot nestlings with nestlings exhibiting slower growth rates in 1996 than in 1997. Food abundance for parrots also varied significantly between years, with greater food availability during the 1997 breeding season than that of 1996. The increased size and growth rates of nestlings in 1997 may have reflected this, and suggests the potential influence of environmental variability on parrot reproduction, particularly in such a markedly seasonal habitat.     

复合微生物菌剂净化规模化养鸡场养殖环境效果研究

试验采用单因子随机分组试验设计,测定了施用复合微生物制菌剂Y30017后对蛋鸡舍内有害气体、鸡粪便排泄物成分的影响,分析该复合微生物菌剂对规模化养鸡场鸡舍环境净化的效果。结果表明:试验组鸡舍氨气浓度和硫化氢浓度分别下降了2.26 mg/kg和1.92 mg/kg(P<0.05);鸡粪排泄物pH值上升1.1%(P<0.05),粗蛋白含量提高了9.17%(P<0.05);每克盲肠内容物中大肠杆菌数量降低了37.17%(P<0.01),乳酸杆菌和双歧杆菌数量分别提高了11.49%和16.17%(P<0.05),未检出沙门氏菌。结果显示,鸡舍主要污染物得到有效控制,养殖环境得到较大改善,使用复合微生物菌剂Y30017控制规模化养鸡场污染物均具有良好的效果,同时可有效提高粪便废弃物的营养值,对养殖废弃物资源化利用具有良好的提质增效作用。     

Microbial Mat Boundaries between Chemolithotrophs and Phototrophs in Geothermal Hot Spring Effluents

Among the various microbial mats that develop in geothermal hot springs in solfataric fields, colorless sulfur-turf (ST)—macroscopic white bundles consisting of large sickle-shaped bacteria belonging to Aquificales and elemental sulfur particles–develops in a limited environment of geothermal effluent containing hydrogen sulfide with neutral pH and low in oxygen. Photosynthetic cyanobacterial mat (CY) often grow just downstream of chemolithotrophic ST, or they coexist with ST where the temperature is slightly lower. Knowledge of the environmental regimes of these microbial mats will lead to better understanding of the distribution of thermophilic microorganisms on the Earth and provide clues about evolutionary processes in the microbial ecosystems of the Precambrian era. We studied the environmental parameters of the boundary zone and examined the distribution of these types of mats and measured the in situ growth rates of the microorganisms composing them. In situ examination revealed that temperature and Eh constrain the development of the microbial mats. At the boundary between ST and CY, temperature and Eh ranged between 51.1°C and 63.2°C and between ?112 mV and ?25 mV, respectively. These environmental parameters were not significantly different among Japanese, Yellowstone (North American), and Icelandic hot spring effluents with genetically similar thermal sulfur oxidizers. Sickle-shaped bacteria rarely coexist with cyanobacteria, although they can potentially grow in some CY environments. This suggests that the boundary between ST and CY might be partly determined by exclusive ecological competition.     

The structure and biogeochemical activity of the phototrophic communities from the Bol'sherechenskii alkaline hot spring

Microbial communities growing in the bed of the alkaline, sulfide hot spring Bol'sherechenskii (the Baikal rift area) were studied over many years (1986-2001). The effluent water temperature ranged from 72 to 74 degrees C, pH was from 9.25 to 9.8, and sulfide content was from 12 to 13.4 mg/ml. Simultaneous effects of several extreme factors restrict the spread of phototrophic microorganisms. Visible microbial fouling appears with a decrease in the temperature to 62 degrees C and in the sulfide content to 5.9 mg/l. Cyanobacteria predominated in all biological zones of the microbial mat. The filamentous cyanobacteria of the genus Phormidium are the major mat-forming organisms, whereas unicellular cyanobacteria and the filamentous green bacterium Chloroflexus aurantiacus are minor components of the phototrophic communities. No cyanobacteria of the species Mastigocladus laminosus, typical of neutral and subacid springs, were identified. Seventeen species of both anoxygenic phototrophic bacteria and cyanobacteria were isolated from the microbial mats, most of which exhibited optimum growth at 20 to 45 degrees C. The anoxygenic phototrophs were neutrophiles with pH optimum at about 7. The cyanobacteria were the most adapted to the alkaline conditions in the spring. Their optimum growth was observed at pH 8.5-9.0. As determined by the in situ radioisotope method, the optimal growth and decomposition rates were observed at 40-32 degrees C, which is 10 to 15 degrees C lower than the same parameter in the sulfide-deficient Octopus Spring (Yellowstone, United States). The maximum chlorophyll a concentration was 555 mg/m2 at 40 degrees C. Total rate of photosynthesis in the mats reached 1.3 g C/m2 per day. The maximum rate of dark fixation of carbon dioxide in the microbial mats was 0.806 g C/m2 per day. The maximum rate of sulfate reduction comprised 0.367 g S/m2 per day at 40 degrees C. The rate of methanogenesis did not exceed 1.188 micrograms C/m2 per day. The role of methanogenesis in the terminal decomposition of the organic matter was insignificant. Methane formation consumed 100 times less organic matter than sulfate reduction.     

A new purple sulfur bacterium isolated from a littoral microbial mat,<Emphasis Type="Italic"> Thiorhodococcus drewsii</Emphasis> sp. nov.

A new strain of purple sulfur bacterium was isolated from a marine microbial mat sampled in Great Sippewissett Salt Marsh at the Atlantic coast (Woods Hole, Mass., USA). Single cells of strain AZ1 were coccus-shaped, highly motile by means of a single flagellum, and did not contain gas vesicles. Intracellular membranes were of the vesicular type. However, additional concentric membrane structures were present. The photosynthetic pigments were bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series, with rhodopin as the dominant carotenoid. Hydrogen sulfide (up to 11 mM), sulfur, thiosulfate, and molecular hydrogen were used as electron donors during anaerobic phototrophic growth. During growth on sulfide, elemental sulfur globules were transiently stored inside the cells. Strain AZ1 is much more versatile than most other Chromatiaceae with respect to electron donor and organic substrates. In the presence of CO(2), it is capable of assimilating C(1)-C(5) fatty acids, alcohols, and intermediates of the tricarboxylic acid cycle. Strain AZ1 could also grow photoorganotrophically with acetate as the sole photosynthetic electron donor. Chemotrophic growth in the dark under microoxic conditions was not detected. Optimum growth occurred at pH 6.5-6.7, 30-35 degrees C, > or =50 micro mol quanta m(-2) s(-1), and 2.4-2.6% NaCl. The DNA base composition was 64.5 mol% G+C. Comparative sequence analysis of the 16S rRNA gene confirmed that the isolate is a member of the family Chromatiaceae. Sequence similarity to the most closely related species, Thiorhodococcus minor DSMZ 11518(T), was 97.8%; however, the value for DNA-DNA hybridization between both strains was only 20%. Because of the low genetic similarity and since strain AZ1 physiologically differs considerably from all other members of the Chromatiaceae, including Trc. minor, the new isolate is described as a new species of the genus Thiorhodococcus, Thiorhodococcus drewsii sp. nov.     

Homoacetogenesis and microbial community composition are shaped by pH and total sulfide concentration

Biological CO₂ sequestration through acetogenesis with H₂ as electron donor is a promising technology to reduce greenhouse gas emissions. Today, a major issue is the presence of impurities such as hydrogen sulfide (H₂S) in CO₂ containing gases, as they are known to inhibit acetogenesis in CO₂-based fermentations. However, exact values of toxicity and inhibition are not well-defined. To tackle this uncertainty, a series of toxicity experiments were conducted, with a mixed homoacetogenic culture, total dissolved sulfide concentrations ([TDS]) varied between 0 and 5 mM and pH between 5 and 7. The extent of inhibition was evaluated based on acetate production rates and microbial growth. Maximum acetate production rates of 0.12, 0.09 and 0.04 mM h^-1 were achieved in the controls without sulfide at pH 7, pH 6 and pH 5. The half-maximal inhibitory concentration (IC₅₀^qAc) was 0.86, 1.16 and 1.36 mM [TDS] for pH 7, pH 6 and pH 5. At [TDS] above 3.33 mM, acetate production and microbial growth were completely inhibited at all pHs. 16S rRNA gene amplicon sequencing revealed major community composition transitions that could be attributed to both pH and [TDS]. Based on the observed toxicity levels, treatment approaches for incoming industrial CO₂ streams can be determined.     

Hydrogen sulfide removal by immobilized Thiobacillus novellas on SiO2 in a fluidized bed reactor

The removal of hydrogen sulfide (H2S) from aqueous media was investigated using Thiobacillus novellas cells immobilized on a SiO2 carrier (biosand). The optimal growth conditions for the bacterial strain were 30 degrees C and initial pH of 7.0. The main product of hydrogen sulfide oxidation by T. novellus was identified as the sulfate ion. A removal efficiency of 98% was maintained in the three-phase fluidized-bed reactor, whereas the efficiency was reduced to 90% for the two-phase fluidized-bed reactor and 68% for the two-phase reactor without cells. The maximum gas removal capacity for the system was 254 g H2S/m3/h when the inlet H2S loading was 300 g/m3/h (1,500 ppm). Stable operation of the immobilized reactor was possible for 20 days with the inlet H2S concentration held to 1,100 ppm. The fluidized bed bioreactor appeared to be an effective means for controlling hydrogen sulfide emissions.     

Inhibition of hydrogen sulfide, methane, and total gas production and sulfate-reducing bacteria in in vitro swine manure by tannins, with focus on condensed quebracho tannins

Management practices from large-scale swine production facilities have resulted in the increased collection and storage of manure for off-season fertilization use. Odor and emissions produced during storage have increased the tension among rural neighbors and among urban and rural residents. Production of these compounds from stored manure is the result of microbial activity of the anaerobic bacteria populations during storage. In the current study, the inhibitory effects of condensed quebracho tannins on in vitro swine manure for reduction of microbial activity and reduced production of gaseous emissions, including the toxic odorant hydrogen sulfide produced by sulfate-reducing bacteria (SRB), was examined. Swine manure was collected from a local swine facility, diluted in anaerobic buffer, and mixed with 1 %?w/v fresh feces. This slurry was combined with quebracho tannins, and total gas and hydrogen sulfide production was monitored over time. Aliquots were removed periodically for isolation of DNA to measure the SRB populations using quantitative PCR. Addition of tannins reduced overall gas, hydrogen sulfide, and methane production by greater than 90 % after 7 days of treatment and continued to at least 28 days. SRB population was also significantly decreased by tannin addition. qRT-PCR of 16S rDNA bacteria genes showed that the total bacterial population was also decreased in these incubations. These results indicate that the tannins elicited a collective effect on the bacterial population and also suggest a reduction in the population of methanogenic microorganisms as demonstrated by reduced methane production in these experiments. Such a generalized effect could be extrapolated to a reduction in other odor-associated emissions during manure storage.     

Ethanol utilization by sulfate-reducing bacteria: an experimental and modeling study

A mixed culture of sulfate-reducing bacteria containing the species Desulfovibrio desulfuricans was used to study sulfate-reduction stoichiometry and kinetics using ethanol as the carbon source. Growth yield was lower, and kinetics were slower, for ethanol compared to lactate. Ethanol was converted into acetate and no significant carbon dioxide production was observed. A mathematical model for growth of sulfate-reducing bacteria on ethanol was developed, and simulations of the growth experiments on ethanol were carried out using the model. The pH variation due to sulfate reduction, and hydrogen sulfide production and removal by nitrogen sparging, were examined. The modeling study is distinct from earlier models for systems using sulfate-reducing bacteria in that it considers growth on ethanol, and analyzes pH variations due to the product-formation reactions.