Effects of environmental factors on microbial induced calcium carbonate precipitation

Aims: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. Methods and Results: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. Conclusions: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. Significance and Impact of Study: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.     

Micro precipitation of lead on the surface of crab shell particles

Crab shell particles were used as a biosorbent to remove lead from aqueous solutions. The equilibrium isotherm showed that crab shell particles took up lead to the extent of 1300 mg Pb g⁻¹ crab shell. The optimum pH range for maximum lead removal was increased to 5·5–11·0 compared to the shell-free control pH of 8·5–11·0. pH values of solutions with crab shell material added were increased spontaneously to about 10 as a result of the CaCO₃ present, which formed complexes with lead according to pH. Electron spectroscopy, Fourier transform infrared spectrometry, scanning electron microscopy and X-ray diffraction results confirmed that -NHCOCH₃ and CO₃² were involved in binding of lead. In addition, the removal of lead occurred mainly through dissolution of CaCO₃ followed by precipitation of Pb₃(CO₃)₂(OH)₂ and PbCO₃ near the surface of crab shell. Micro precipitates formed were then adsorbed to the chitin on the surface of the crab shell particles.     

Improved strength and durability of fly ash-amended concrete by microbial calcite precipitation

Fly ash acts as a partial replacement material for both Portland cement and fine aggregate. An innovative approach of microbial calcite precipitation in fly ash-amended concrete has been investigated. This is the first report to discuss the role of microbial calcite precipitation in enhancing the durability of fly ash-amended concrete. The present study investigated the effects of Bacillus megaterium ATCC 14581 on compressive strength, water absorption and water impermeability of fly ash-amended mortar and concrete. Mortar specimens were used for compressive strength and water absorption tests, while concrete specimens were used for water impermeability tests. At the fly ash concentrations of 10%, 20% and 40% in mortars, bacterial cell enhanced mortar compressive strength by 19%, 14% and 10%, respectively, compared to control specimens. Treated mortar cubes absorbed more than three times less water than control cubes as a result of microbial calcite deposition. Microbial deposition of a layer of calcite on the surface of the concrete specimens resulted in substantial decrease of water uptake and permeability compared to control specimens without bacteria. Microbial cells also prevented ingress of water effectively in different concentrations of fly ash-amended concrete. Scanning Electron Micrography (SEM) analyses evidenced the direct involvement of bacteria in calcite precipitation. The approach of the present study gives us dual environment friendly advantages. First, use of fly ash-a recovered resource reduces depletion of natural resources and also reduces the energy-intensive manufacturing of other concrete ingredients, leading to savings in both energy usage and emissions of greenhouse gases. And second, use of bacterial cells to improve strength and durability of fly ash-amended concrete further provides greener and economic options.     

Key roles of pH and calcium metabolism in microbial carbonate precipitation

This paper reviews the general mechanismsof microbial carbonate precipitation and offersan alternative view on the role of calciummetabolism in this process, as well as on theoccurrence of species- and environment-specificcalcification.     

Mathematical modeling of precipitation and dissolution reactions in microbiological systems

We expand the biogeochemical model CCBATCH to include a precipitation/dissolution sub-model that contains kinetic and equilibrium options. This advancement extends CCBATCH's usefulness to situations in which microbial reactions cause or are affected by formation or dissolution of a solid phase. The kinetic option employs a rate expression that explicitly includes the intrinsic kinetics for reaction ormass-transport control, the differencefrom thermodynamic equilibrium, and the aqueous concentration of the rate-limiting metal or ligand. The equilibrium feature can be used alone, and it also serves as check that the kinetic rate never is too fast and ``overshoots' equilibrium. The features of the expanded CCBATCH are illustrated by an example in which the precipitation of Fe(OH)_{3 (s)} allows the biodegradation of citric acid, even though complexes are strong and not bioavailable. Precipitation releases citrate ligand, and biodegradation of the citrate increases the pH.     

半干旱矿区侵蚀营力对黑沙蒿根系生长特性的影响及其自修复

以半干旱矿区典型分布的黑沙蒿为研究对象,通过野外原位不离体试验,模拟侵蚀拉拔破坏对黑沙蒿根系生长特性的影响,并分析其受损自修复能力,旨在揭示植物根系在脆弱生态区中抵御外力侵蚀的生存策略.结果 表明,拉拔破坏形成机械损伤后,根系生长速率和活性均明显降低,持续拉拔对二者的抑制作用显著大于瞬时拉拔,重度损伤产生的负反馈显著大...     

Stoichiometry and kinetics of microbial toluene degradation under denitrifying conditions

Batch experiments were carried out to investigate the stoichiometry and kinetics of microbial degradation of toluene under denitrifying conditions. The inoculum originated from a mixture of sludges from sewage treatment plants with alternating nitrification and denitrification. The culture was able to degrade toluene under anaerobic conditions in the presence of nitrate, nitrite, nitric oxide, or nitrous oxide. No degradation occurred in the absence of Noxides. The culture was also able to use oxygen, but ferric iron could not be used as an electron acceptor. In experiments with¹⁴C-labeled toluene, 34%±8% of the carbon was incorporated into the biomass, while 53%±10% was recovered as¹⁴CO₂, and 6%±2% remained in the medium as nonvolatile water soluble products. The average consumption of nitrate in experiments, where all the reduced nitrate was recovered as nitrite, was 1.3±0.2 mg of nitrate-N per mg of toluene. This nitrate reduction accounted for 70% of the electrons donated during the oxidation of toluene. When nitrate was reduced to nitrogen gas, the consumption was 0.7±0.2 mg per mg of toluene, accounting for 97% of the donated electrons. Since the ammonia concentration decreased during degradation, dissimilatory reduction of nitrate to ammonia was not the reductive process. The degradation of toluene was modelled by classical Monod kinetics. The maximum specific rate of degradation, k, was estimated to be 0.71 mg toluene per mg of protein per hour, and the Monod saturation constant, K _s , to be 0.2 mg toluene/l. The maximum specific growth rate, _max , was estimated to be 0.1 per hour, and the yield coefficient, Y, was 0.14 mg protein per mg toluene.Abbreviations NVWP Non Volatile Water-soluble Products     

Effect of alcohol chain length on the optimum conditions for lipase-catalyzed synthesis of adipate esters

Immobilized Candida antarctica lipase B, Novozym® 435, was used in the esterification of adipic acid and alcohols with different chain lengths (C₁–C₁₈). Optimum conditions for the synthesis of adipate esters were obtained using response surface methodology (RSM) with respect to important reaction parameters including time, temperature, substrate molar ratio and amount of enzyme. Alcohol chain length specificity of the enzyme in the synthesis of adipate esters was also determined. Minimum reaction time (215 min) for achieving maximum ester yield was obtained for butyl alcohol. Methanol required an increased time (358 min) and enzyme amount (10.2%, w/w) for attaining maximum yield. The maximum required temperature and time of 65°C and 523 min, respectively, were obtained for the synthesis of dioctadecyl adipate. The results demonstrate that alcohol chain length is a determining parameter in optimization of the lipase-catalyzed synthesis of adipate esters. Reactions under optimized conditions yielded a high percentage of esterification (>97%). The optimum conditions can be used to scale up the process.     

Characteristics and turnover of exopolymeric substances in a hypersaline microbial mat

The properties and microbial turnover of exopolymeric substances (EPS) were measured in a hypersaline nonlithifying microbial mat (Eleuthera, Bahamas) to investigate their potential role in calcium carbonate (CaCO₃) precipitation. Depth profiles of EPS abundance and enzyme activities indicated that c . 80% of the EPS were turned over in the upper 15–20 mm. Oxic and anoxic mat homogenates amended with low-molecular-weight (LMW) organic carbon, sugar monomers, and different types of EPS revealed rapid consumption of all substrates. When comparing the consumption of EPS with that of other substrates, only marginally longer lag times and lower rates were observed. EPS (5–8%) were readily consumed during the conversion of labile to refractory EPS. This coincided with a decrease in glucosidase activity and a decrease in the number of acidic functional groups on the EPS. Approximately half of the calcium bound to the EPS remained after 10 dialyses steps. This tightly bound calcium was readily available to precipitate as CaCO₃. We present a conceptual model in which LMW organic carbon complexed with the tightly bound calcium is released upon enzyme activity. This increases alkalinity and creates binding sites for carbonate and allows CaCO₃ to precipitate. Therefore, this model explains interactions between EPS and CaCO₃ precipitation, and underscores the critical role of aerobic and anaerobic microorganisms in early diagenesis and lithification processes.     

谷氨酰胺转胺酶发酵条件的优化研究

通过优化种子培养条件和发酵培养基组分使谷氨酰胺转胺酵产酶水平有了很大的提高,确定种龄为20－24h,接种量8％左右。发酵培养基含淀粉15g/L、葡萄糖15g/L、蛋白胨25g/L、酵母膏3g/L、无水硫酸镁2g/L、磷酸氢二2g/L,无水磷酸二氢钾2g/L,24－28h添加质量浓度为0．5％的硫酸铵,在10L发酵罐实验中,验证了溶解氧对MTG合成至关重要,确定较适宜通气量1：1．25vvm,搅拌转速300mr/min,最高产酶单位最终稳定在3．2u/mL,放罐时间在44－46h左右较适宜。     

A Novel Approach to Enhance the Urease Activity of Sporosarcina pasteurii and its Application on Microbial-Induced Calcium Carbonate Precipitation for Sand

Abstract

Urease is involved in the formation of carbonate sediments by microbial-induced calcium carbonate precipitation (MICP), and Sporosarcina pasteurii used extensively in this technique owing to its high urease production. In this study, a simple two-step culture method with the appropriate medium was developed to enhance the urease activity of S. pasteurii. Urea played an important role in the culture process, particularly during the pre-cultivation step and the newly developed method improved both urease activity and specific urease activity. Furthermore, the increase in urease activity by MICP resulted in increased production of calcium carbonate and better strength of bio-cemented sand.     

Comparison of microbially induced calcium carbonate precipitation eligibility using sporosarcina pasteurii and bacillus licheniformis on two different sands

The use of biological means for ground improvement have become popular, which generally works through the process called microbially-induced calcium carbonate precipitation (MICP). Many studies indicate successful application of MICP based improvement with multiple bacteria and on several soils. Given the proven performance of MICP, this study aims to examine the MICP process by comparing the calcium carbonate precipitation ability of widely studied bacteria, i.e., Sporosarcina pasteurii and relatively under-recognized bacteria, i.e., Bacillus licheniformis to outline the formation success. For this purpose, two different sands were tested for observing precipitation behavior using a series of syringe tests. Furthermore, the effect of concentration and inclusion of calcium chloride for nutrition of bacteria, saturation with water, and hybrid use of two bacteria were investigated in some tests for diversification. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS) were used for the interpretation of results. Results indicated that Sporosarcina pasteurii had performed superior over Bacillus licheniformis when achieving calcium carbonate precipitation in tests for both sands. In addition, many intriguing SEM images contributed to the literature of MICP monitoring, highlighting the effects of the variables investigated.     

Isolation and metagenomic characterization of bacteria associated with calcium carbonate and struvite precipitation in a pure moving bed biofilm reactor-membrane bioreactor

A bench-scale pure moving bed bioreactor-membrane bioreactor (MBBR-MBR) used for the treatment of urban wastewater was analyzed for the identification of bacterial strains with the potential capacity for calcium carbonate and struvite biomineral formation. Isolation of mineral-forming strains on calcium carbonate and struvite media revealed six major colonies with a carbonate or struvite precipitation capacity in the biofouling on the membrane surface and showed that heterotrophic bacteria with the ability to precipitate calcium carbonate and struvite constituted ~7.5% of the total platable bacteria. These belonged to the genera Lysinibacillus, Trichococcus, Comamomas and Bacillus. Pyrosequencing analysis of the microbial communities in the suspended cells and membrane biofouling showed a high degree of similarity in all the samples collected with respect to bacterial assemblage. The study of operational taxonomic units (OTUs) identified through pyrosequencing suggested that ~21% of the total bacterial community identified in the biofouling could potentially form calcium carbonate or struvite crystals in the pure MBBR-MBR system used for the treatment of urban wastewater.     

微生物除臭剂发酵工艺条件优化及硫素转化的研究

利用酵母菌、乳酸菌、醋酸菌三种可食性微生物复配发酵制备微生物除臭剂,研究微生物复配比、发酵时间、发酵温度、接种量四个因素对H_2S去除率的影响。以单因素实验为基础,利用Box-Behnken响应面法优化最佳发酵条件,进一步研究硫元素转化及含量动态变化。结果表明酵母菌、乳酸菌、醋酸菌质量比为1∶2∶2时,各因素对H_2S去除率的影响由高到低依次为发酵温度发酵时间接种量,最优发酵条件为发酵时间48. 5 h、发酵温度30℃、接种量12. 75%,H_2S的去除率可达到71. 84%;实验组与对照组的硫元素转化及含量动态变化相比,实验组的SO_4~(2-)含量显著较高(P0. 05),H_2S释放量显著较低(P0. 05)说明该微生物除臭剂可以调节硫元素转化,有效抑制H_2S产生。     

A study of the optimum drying conditions for cabbage seed following selection on the basis of a newly-emerged radicle

A series of experiments were carried out to study the effects of different drying regimes on the survival of newly-germinated (radicle emerged 0·5-1·5 mm through the seed coat) cabbage seeds and to establish a treatment for reducing the moisture content of these germinated seeds. A preliminary surface-drying step proved necessary to avoid seed agglutination during the main drying stage. Of the drying regimes compared both viability and vigour were most effectively maintained in air, conditioned to between 20 and 30°C and with 80% r.h., flowing through the seeds at 0·25 m s^-1. Under these conditions, the viability and vigour of newly-germinated seed was maintained during drying to an equilibrium moisture content of c. 14%. At this moisture content further radicle growth was prevented and seeds remained free-flowing and separate for sowing or for further treatment.     

天然碱泥絮凝用微生物絮凝剂产生条件的研究

报道了内蒙天然碱碱泥絮凝用微生物絮凝剂适宜产生条件的研究结果。高糖低氮培养基有利于絮凝剂的产生。适宜摇床发酵条件为：初始PH值7．5－8．5,培养温度30℃,摇床转速180r/min,发酵60h;在摇床优化的培养条件的基础上进行5L罐放大试验,发酵周期缩短12h,絮凝活性提高了14．45％。     

不同培养条件对胶质芽孢杆菌诱导碳酸钙晶体形成的影响

【目的】研究不同培养条件对胶质芽孢杆菌(Bacillus mucilaginosus)菌体形态、数量和分泌的碳酸酐酶(CA酶)活性的影响,以及不同方式培养的菌体与碳酸钙晶体的生长及其形貌、数量之间的联系。【方法】分别采用无氮和有氮培养基培养胶质芽孢杆菌,进行菌体形态、数量及CA酶活性的比较,收集不同培养方式的菌体加入碳酸钙结晶体系中以研究细菌与碳酸钙晶体形成的联系。【结果】在无氮培养条件下,胶质芽孢杆菌数量少、荚膜肥厚,细菌培养液CA酶活力较低;有氮培养条件下,菌体数量多、荚膜单薄,细菌培养液CA酶活力较高。在碳酸钙结晶体系中加入无氮培养的菌体,生成的碳酸钙晶体表面光滑,体积较大但数量较小,加入有氮条件下培养的菌体形成的碳酸钙晶体表面粗糙,数量大但体积较小。【结论】不同培养条件能够引起胶质芽孢杆菌菌体数量、荚膜多糖及CA酶活的明显差异,进而对碳酸钙晶体的生成和形貌产生影响。     

Annual growth layers as proxies of past growth conditions for benthic microbial mats in a perennially ice-covered Antarctic lake

Perennial microbial mats can be the dominant autotrophic community in Antarctic lakes. Their seasonal growth results in clearly discernible annual growth layering. We examined features of live microbial mats from a range of depths in Lake Hoare, Antarctica, that are likely to be preserved in these layers to determine their potential as proxies of past growth performance. Cyanobacteria dominated the mat for all but the deepest depth sampled. Changes in areal concentrations of phycobilin pigments, organic matter and extracellular polysaccharide and in species composition did not correspond to changes in various water column properties, but showed a linear relationship with irradiance. Carbonate accumulation in the mats correlated with biomass markers and may be inferred as an index of mat performance. We examined the carbonate content of annual layers laid down from 1958–1959 to 1994–1995 in sediment cores from 12 m depth. The carbonate content in the layer showed a significant correlation with the mean summer air temperature. These data suggest a link between air temperature and microbial mat growth performance, and suggest that it is mediated via irradiance. Laminated microbial mats in Antarctic lakes have the potential to act as fine-resolution records of environmental conditions in the recent past, although interpretation is complex.