Advances in Microbial Remediation on the Application of Heavy Metal Pollution in Agricultural Water Resources

Heavy metal pollution in agricultural water resources is very serious in re- cent years, resulting in large losses of the agricultural economy and endangering human life and health. Due to the advantages of low cost, high efficiency and less secondary pollution, microbial ramediation technology is widely used in the treatment of heavy metal pollution in agricultural water resources. At present, with the progress of modern biotechnology, microbial remediation of heavy metals in agricul- tural water resources has grown rapidly. The sources and status quo of heavy met- al pollution in agricultural water resources at home and aboard, and the principles of microbial remediation of heavy metals pollution in agricultural water resources were reviewed in this paper, as well as the several common microbial remediation technology of heavy metals in agricultural water resources. Additionally, the further research work of heavy metal contaminated agricultural water resources by microbial ramediation were prospected.

Evaluating Microbial Water Quality and Potential Sources of Fecal Contamination in the Musconetcong River Watershed in New Jersey, USA

Microbial pathogens and indicators have contributed to major part of water quality degradation in the United States. Located in the northwestern New Jersey, the Musconetcong River has been included in the New Jersey Impaired Waters List or the 303(d) List due to high concentrations of fecal indicator bacteria. Hence, a Total Maximum Daily Load plan was established to address microbial water quality issues in the watershed. The objectives of this study were to assess the current status of microbial water quality and to determine potential sources of fecal contamination in the Musconetcong River Watershed using microbial source tracking techniques. Fifteen sampling events in total were carried out at nine sites throughout the Musconetcong River Watershed in August 2016, July and August 2017. E. coli enumeration was performed to determine the possible presence of fecal contaminations. Microbial source tracking techniques, specifically Canada goose, cow, deer, horse, and human-specific molecular markers, were used for real-time polymerase chain reaction (qPCR) analysis in order to identify and quantify potential sources of fecal contamination. The results indicated that E. coli was found present at all nine study sites. Two of the nine sites violated the New Jersey Surface Water Quality Standards in August 2016, while all of the nine sites exceeded the standards in both July and August 2017. Water temperature, dissolved oxygen (DO), and specific conductance at the study sites ranged from 13.5?C to 25.3?C, from 7.7 mg/L to 13.0 mg/L, and 278.5 μS/cm to 1335.0 μS/cm, respectively, at the time of sample collection. E. coli counts were found to be negatively correlated with temperature and specific conductance (p p < 0.05). Higher percentage of presence of human, Canada goose and deer markers were observed at all fifteen sampling events indicating human and wildlife were the two major sources of fecal contaminations in the Musconetcong River Watershed. The study suggested applying restoration measures to reduce fecal contaminations from anthropogenic and wildlife sources in order to improve microbial water quality of the Musconetcong River. However, more frequent and strategic sampling plan is recommended to supply more comprehensive data to aid in future planning of best management efforts on controlling fecal contaminations.

Gas Sources of Natural Gas Hydrates in the Shenhu Drilling Area, South China Sea: Geochemical Evidence and Geological Analysis

The Shenhu gas hydrate drilling area is located in the central Baiyun sag, Zhu I! depression, Pearl River Mouth basin, northern South China Sea. The gas compositions contained in the hydrate-bearing zones is dominated by methane with content up to 99.89% and 99.91%. The carbon isotope of the methane （δ^13C1） are -56.7%0. and -60.9%0, and its hydrogen isotope （δD） are -199%0 and -180%0, respectively, indicating the methane from the microbial reduction of CO2. Based on the data of measured seafloor temperature and geothermal gradient, the gas formed hydrate reservoirs are from depths 24-1699 m below the seafloor, and main gas-generation zone is present at the depth interval of 416-1165 m. Gas-bearing zones include the Hanjiang Formation, Yuehai Formation, Wanshan Formation and Quaternary sediments. We infer that the microbial gas migrated laterally or vertically along faults （especially interlayer faults）, slump structures, small-scale diapiric structures, regional sand beds and sedimentary boundaries to the hydrate stability zone, and formed natural gas hydrates in the upper Yuehai Formation and lower Wanshan Formation, probably with contribution of a little thermogenic gas from the deep sedments during this process.

Functional diversity of soil microbial communities in response to supplementing 50% of the mineral N fertilizer with organic fertilizer in an oat field

The effects of supplementing 50%of the mineral N fertilizer with organic fertilizer on the metabolism and diversity of soil microbial communities in an oat field were investigated using Biolog-Eco plates.The experiment consisted of five treatments:no fertilizer(CK),mineral N fertilizer applied at 90 and 45 kg ha^(-1) N in the form of urea(U1 and U2,respectively),and U2 supplemented with organic fertilizer in the form of sheep manure at 90 and 45 kg ha^(-1) N(U2OM1 and U2OM2,respectively).Each treatment had three replications.The experiment was conducted in 2018 and 2019 in Pinglu District,Shanxi Province,China.The carbon source utilization by soil microbial communities,such as amino acids,amines,carbohydrates,carboxylic acids,and polymers,increased when 50%of the mineral N fertilizer was replaced with organic fertilizer in both years.This result was accompanied by increased richness,dominance,and evenness of the microbial communities.The utilization of amino acid,amine,and carboxylic acid carbon sources and community evenness were further improved when the organic fertilizer amount was doubled in both years.Biplot analysis indicated that amines and amino acids were the most representative of the total carbon source utilization by the soil microbial communities in both years.The highest oat yield was achieved at a total N application rate of 135 kg ha^(-1) in the treatment involving 45 kg ha^(-1) N in the form of urea and 90 kg ha^(-1) N in the form of sheep manure in both years.It was concluded that the application of 50%of the conventional rate of mineral N fertilizer supplemented with an appropriate rate of organic fertilizer enhanced both the functional diversity of soil microbial communities and oat yield.Amine and amino acid carbon sources may be used as a substitute for total carbon sources for assessing total carbon source utilization by soil microbial communities in oat fields in future studies.

Differences in carbon source usage by dental plaque in children with and without early childhood caries

Early childhood caries （ECC） is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provided significant information regarding the connection between dental caries and oral micmbiomes, further comprehension of this microbial community＇s ecological relevance is limited. This study identified the carbon source metabolic differences in dental plaque between children with and without ECC. We compared the microbial community functional diversity in 18 caries-free subjects with 18 severe ECC patients based on sole carbon source usage using a Biolog assay. The anaerobic microbial community in the ECC patients displayed greater metabolic activity than that of the control group. Specific carbon source metabolism differed significantly between the two groups. Subjects from the two groups were well distinguished by cluster and principal component analyses based on discriminative carbon sources. Our results implied that the microbial functional diversity between the ECC patients and healthy subjects differed significantly. In addition, the Biolog assay furthered our understanding of oral microbiomes as a composite of functional abilities, thus enabling us to identify the ecologically relevant functional differences among oral microbial communities.

Effects of Carbon and Nitrogen Additions on Soil Microbial Biomass Carbon and Enzyme Activities Under Rice Straw Returning

The effects of different amounts of carbon and nitrogen sources on the soil microbial biomass carbon,dissolved organic carbon and related enzyme activities were studied by the simulation experiment of rice straw returning to the field,and the mechanism of the decomposition of rice straw returning to the field was discussed.Completely randomized experiment of the two factors of the three levels was designed,and a total of nine treatments of indoor soil incubation tests were conducted.Full amount of rice straw was applied to the soil in this simulation experiment and different amounts of brown sugar and urea were added in the three levels of 0(no carbon source and nitrogen source),1(low levels of carbon and nitrogen sources)and 2(high levels of carbon and nitrogen sources),respectively.The results showed that the addition of different amounts of carbon and nitrogen sources to the rice straw could increase the soil carbon content.Compared with T0N0,the microbial biomass carbon of T2N2 was increased significantly by 170.48%;the dissolved organic carbon content of T1N2 was significantly increased by 58.14%and the free humic acid carbon contents of T0N2,T1N1 and T2N0 were significantly increased by 56.16%and 45.55%and 47.80%,respectively;however,there were no significant differences among those of treatments at later incubation periods.The addition of different carbon and nitrogen sources could promote the soil enzyme activities.During the incubation period,all of the soil enzyme activities of adding sugar and urea were higher than those of T0N0 treatment.Therefore,the addition of different amounts of carbon and nitrogen sources to rice straw returning could improve soil microbial biomass carbon content,dissolved organic carbon and soil enzyme activities.

Microbial Fuel Cell Technique for Environment Monitoring

The increasingly serious environment pollution has put forward higher and higher requirement for environment monitoring technique,and conventional environment monitoring methods could not satisfy the requirements from industrial development. Microbial fuel cells( MFCs) could be used for online BOD monitoring,toxicity detection,microbial activity detection and microbial quantity detection,and as power sources for environment monitoring sensors. The technique has the advantages of simple and rapid operation,high sensitivity and good reproducibility,and serve is capable of performing online in-situ monitoring. It is the newest environment monitoring technique,with a broad application prospect. In this paper,the studies and application of MFCs in environment monitoring field were reviewed,and main existing problems were analyzed,so as to provide reference for future study.

Insight into the microbial community of denitrification process using different solid carbon sources: Not only bacteria

There is a lack of understanding about the bacterial,fungal and archaeal communities’composition of solid-phase denitrification(SPD)systems.We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit(OTU)and amplicon sequence variant(ASV).The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone(CPSP,0.86±0.04 mg NO_(3)^(−)-N/(g·day))and corncob(0.85±0.06 mg NO_(3)^(−)-N/(g·day))had better denitrification efficiency than polycaprolactone(PCL,0.29±0.11 mg NO_(3)^(−)-N/(g·day))and polyvinyl alcoholsodium alginate(PVA-SA,0.24±0.07 mg NO_(3)^(−)-N/(g·day)).The bacterial,fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL(OTU:83.72%,ASV:82.49%)and Rozellomycota in PVA-SA(OTU:71.99%,ASV:81.30%).ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum,unclassified_f_Xanthobacteraceae genus,etc.,indicating ASV may be more conducive to understand SPD microbial communities.The co-occurring network showed some correlation between the bacteria fungi and archaea species,indicating different species may collaborate in SPD systems.Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems.These results may be beneficial for understanding microbial communities in SPD systems.

An Experimental Study of Microbial Fuel Cells for Electricity Generating: Performance Characterization and Capacity Improvement

This paper studies the electricity generating capacity of microbial fuel cells (MFCs). Unlike most of MFC research, which targets the long term goals of renewable energy production and wastewater treatment, this paper considers a niche application that may be used immediately in practice, namely powering sensors from soils or sediments. There are two major goals in this study. The first goal is to examine the performance characteristics of MFCs in this application. Specifically we investigate the relationship between the percentage of organic matter in a sample and the electrical capacity of MFCs fueled by that sample. We observe that higher percentage of organic matter in a sample results in higher electricity production of MFCs powered by that sample. We measure the thermal limits that dictate the temperature range in which MFCs can function, and confirm that the upper thermal limit is 40℃. The new observation is that the lower thermal limit is -5℃, which is lower than 0℃ reported in the literature. This difference is important for powering environmental sensors. We observe that the electricity production of MFCs decreases almost linearly over a period of 10 days. The second goal is to determine the conditions under which MFCs work most efficiently to generate electricity. We compare the capacity under a variety of conditions of sample types (benthic mud, top soil, and marsh samples), temperatures (0℃, 40℃, and room temperature), and sample sizes (measuring 3.5 cm × 3.5 cm × 4.6 cm, 10.2 cm × 10.2 cm × 13.4 cm, and 2.7 cm × 2.7 cm × 3.8 cm), and find that the electricity capacity is greatest at 0℃, powered by benthic mud sample with the largest chamber size. What seems surprising is that 0℃ outperforms both room temperature and benthic mud sample outperforms marsh sample, which appears to be richer in organic matter. In addition, we notice that although the largest chamber size produces the greatest capacity, it suffers from efficiency loss. The reasons of these observations will be explained in the paper. The study demonstrates that the electricity production of MFCs can be increased by selecting the right condition of sample type, temperature, and chamber size.

Fecal scores and microbial metabolites in weaned piglets fed different protein sources and levels

This experiment studied the effects of dietary protein sources and levels on the gut health of piglets,p H value,and concentrations of microbial metabolites(ammonia-N,volatile fatty acids [VFA],and polyamines) in the distal colonic and proximal colonic digesta of piglets weaned at 21 d of age.A total of 150 early-weaned piglets were allotted randomly to 5 diets: 1) control diet(CT; 17% CP),2) CT formulated with more soy protein concentrate(SPC19; 19% CP),3) more fish meal(FM19; 19% CP),4) CT formulated with more soy protein concentrate(SPC23; 23% CP),and 5) more fish meal(FM23; 23%CP).Results showed high protein level increased fecal score(P < 0.05),but different protein sources did not(P > 0.05).The p H value and ammonia-N concentration of digesta in the proximal and distal colon of FM23 were significantly higher(P < 0.05) than those of CT.Acetic acid,propionic acid,butyric acid and valeric acid concentrations in the proximal colon of FM23 exceeded those of CT,SPC19,and FM19(P < 0.05);however,isobutyric acid and isovaleric acid were not affected(P > 0.05).Histamine and spermidine concentrations of FM23 were higher than those of other treatments(P < 0.05).Propionic acid and butyric acid concentrations in the distal colon were higher of FM23 than of FM19(P < 0.05); putrescine,histamine and spermidine were higher of FM23 than of LP and FM19(P < 0.05).It was concluded that high dietary CP content increased microbial metabolites(ammonia-N,histamine,putrescine) in colonic digesta and aggravated piglets' diarrhea.

Denitrification and microbial community in MBBR using A. donax as carbon source and biofilm carriers for reverse osmosis concentrate treatment

In this study,raw Arundo donax(A.donax)pieces were applied as carbon source and biofilm carriers for denitrification in a lab-scale moving bed biofilm reactor(MBBR)for the treatment of reverse osmosis concentrate gathered from local wastewater reuse plant.At stable phase(about 60 days),efficient denitrification performance was obtained with73.2%±19.5%NO3--N average removal and 8.10±3.45 g N/(m3·day)NO3--N average volumetric removal rate.Mass balance analysis showed that 4.84 g A.donax was required to remove 1 g TN.Quantitative real-time PCR analysis results showed that the copy numbers of 16S r-RNA,narG,nirS,nosZ and anammox gene of carrier biofilm and suspended activated sludge in the declination phase(BF2 and AS2)were lower than those of samples in the stable phase(BF1 and AS1),and relatively higher copy numbers of nirS and nirK genes with lower abundance of narG and nosZ genes were observed.High-throughput sequencing analysis was conducted for BF2 and AS2,and similar dominant phyla and classes with different abundance were obtained.The class Gammaproteobacteria affiliated with the phylum Proteobacteria was the most dominant microbial community in both BF2(52.6%)and AS2(41.7%).The PICRUSt prediction results indicated that 33 predictive specific genes were related to denitrification process,and the relative abundance of 18 predictive specific genes in BF2 were higher than those in AS2.

Changes of Soil Microbiological Characteristics After Solidago canadensis L. Invasion

The relationship between Solidago canadensis L. invasion and soil microbial communities was studied across the invasive gradients varying from 0 to 40, 80, and 100% coverage of S. canadensis. The results showed both soil microbial biomass C （Cmic） and N （Nmic） increased as the coverage of S. canadensis increased. Soil microbial quotient Cmic/Corg （microbial biomass C/organic C） tended to increase linearly with the coverage of S. canadensis. Soil basal respiration （BR） also showed a similar trend. The soil respiratory quotient qCO2 decreased with S. canadensis invasion, and remained at quite a constantly low level in the invasive soils. Sole carbon source utilization profiles analyses indicated that S. canadensis invasion tended to result in higher microbial functional diversity in the soil. Average utilization of specific substrate guilds was highest in the soil with S. canadensis monoculture. Principle component analysis of sole carbon source utilization profiles further indicated that microbial functional diversity in the soil with S. canadensis monoculture was distinctly separated from those soils in the native area and the ecotones. In conclusion, S. canadensis invasion improved soil microbial biomass, respiration and utilization of carbon sources, and decreased qCO2, thus created better soil conditions, which in turn were more conducive to the growth of S. canadensis.

Assembly process and source tracking of microbial communities in sediments of Dongting Lake

●Soil erosion resulted in homogenization of bacterial communities in the watershed.●Microbial community heterogeneity among erosion sites made soil tracing possible.●Assembly process results showed that the tracking results can achieve high precision.●Dryland was the main source of sediment deposition based on the result of FEAST.Sediment source tracing can accurately provide a theoretical basis for controlling soil erosion effectively,by identifying the most serious types of land use.Traditional sediment tracing methods are based on physical,chemical,biological,and composite fingerprinting,which have not included microbes.As high-throughput sequencing becomes more prevalent,microorganisms can provide more information than what we think.Thus,whether the microorganism can also be used as a special fingerprint factor for sediment source identification during soil erosion,we have tested it by using microbial source tracking tool FEAST to quantify the microbe contribution from five types of eroded land(including dryland,urban,paddy field,forest and grassland)to the depositional areas(Niubitan)in the Yuanjiang basin.The source microbial community in the erosive area was heterogeneous,and assembly process analysis further demonstrated that the source tracking results could reach higher accuracy.The results of FEAST showed that dryland(35.50%),urban(17.21%),paddy field(8.14%),and forest(1.07%)were the major contributors to Niubitan.Our results follow the general soil erosion rules and prove its validity.Taken together,a new perspective is provided by these results for tracing sediment sources in erosion-sedimentary systems.

Validation of Bacteroidales-based microbial source tracking markers for pig fecal pollution and their application in two rivers of North China

In China,pig feces is the predominant source of excrement produced b y animal husbandry.Improper use or direct discharge of pig feces can result in contamination of natural water systems.Microbial source tracking(MST)technology can identify the sources of fecal pollution in environmental water,and contribute to the management of pig fecal pollution by local environmental protection agencies.However,the accuracy of such assays can be context-dependent,and they have not been comprehensively evaluated under Chinese conditions.We aimed to compare the performance of five previously reported nig-specific MST assays(PF,Pig-Bac 1 STBR,Pig-Bac2 SYBR,Pig-1-Bac TaqMan,and Pig-2-Bac TaqMan,which are based on Bacteroidales 16S rRNA gene markers)and apply them in two rivers of North China.We collected a total of 173 fecal samples from pigs,cows,goats,chickens,humans,and horses across China.The PF assay optimized in this study showed outstanding qualitative performance and achieved 100%specificity and sensitivity.However,the two SYBR green qPCR assays(Pig-Bac1 SYBR and Pig-Bac2 SYBR)cross-reacted with most non-pig fecal samples.In contrast,both the Pig-l-Bac TaqMan and Pig-2-Bacr TaqMan assays gave 100%specificity and sensitivity.Of these,the Pig-2-Bac TaqMan assay showed higher reproducibility.Our results regarding the specificity of these pig-specific MST assays differ from those reported in Thailand,Japan,and America.Using the PF and Pig-2-Bac TaqMan assays,a field test comparing the levels of pig fecal pollution in rivers near a pig farm before and after comprehensive environmental pollution governance indicated that pig fecal pollution was effectively controlled at this location.

不同粗饲料来源对湖羊羔羊盲肠菌群结构及功能的影响

选用7日龄[(3.77±0.46)kg]湖羊公羔60只,随机分为4个处理组,饲草来源组饲喂苜蓿(Medicago sativa)干草(alfalfa hay,AH)和燕麦(Avenasativa)干草(oat hay,OH),非饲草来源组饲喂甜菜(Betavulgaris)粕(beet pulp,BP)和大豆(Glycine max)皮(soybean hulls,SH)。70日龄时饲养试验结束,各组随机屠宰6只羔羊,获得24个盲肠内容物样品以备16S rDNA测序,研究饲粮粗饲料来源对湖羊羔羊盲肠内容物菌群结构和功能的影响。结果表明:24个盲肠内容物样品共获得72482条有效数据与2999个OTU,物种注释共获得12个门、54个纲、103个目、174个科和349个属;OH组物种数、辛普森指数和香农指数显著高于AH组(P<0.05);盲肠以厚壁菌门和拟杆菌门为核心菌门;瘤胃球菌科为优势菌科;OH组毛螺旋菌科显著高于AH和SH组(P<0.05),克里斯滕森菌科显著高于AH组和BP组(P<0.05);BP组变形菌门显著高于AH、SH和OH组(P<0.05),毛螺旋菌科极显著高于AH和SH组(P<0.01);SH和OH组未鉴定的丹毒丝菌属显著高于AH和BP组。使用Tax4Fun法的预测分析得出湖羔羊盲肠菌群以碳水化合物代谢、脂类、能量和氨基酸代谢为主。相关性分析Muribaculaceae菌科与活体重和日增重之间呈显著正相关关系(P<0.05),普雷沃氏菌科与活体重和日增重之间呈显著负相关关系(P<0.05)。综上所述,开食料不同粗饲料来源由于其纤维素结构不同,对湖羊羔羊盲肠微生物菌群结构及功能作用具有较大差异。

酱香型白酒堆积发酵过程中真菌的结构及其来源分析

堆积发酵是酱香型白酒酿造工艺中最难掌握的关键环节,该过程是环境微生物参与白酒发酵的“窗口”。真菌群落被认为是酱香型白酒糖化及产酒的主要贡献者,该研究旨在揭示堆积发酵过程中真菌的演替规律及可能来源,为管理和调控堆积发酵提供生物学依据。该研究采用高通量测序技术分析真菌群落,并通过三相图和SourceTracker分析真菌来源和比例。结果表明,堆积过程中真菌多样性随时间延长显著下降,表明堆积过程对真菌的强烈选择作用。堆积过程的优势真菌主要包括:毕赤酵母属(Pichia,平均相对丰度82.75%)、酿酒酵母属(Saccharomyces,5.75%)、嗜热子囊菌(Thermoascus,2.75%)、曲霉属(Aspergillus,2.25%)和红曲霉属(Monascus,1.12%)等。溯源分析表明大曲(平均贡献比例33.14%)主要贡献霉菌等;操作环境(平均贡献比例66.71%)主要贡献酵母类微生物。该研究强调了堆积发酵对核心微生物的富集作用,大曲及操作环境共同贡献功能微生物的来源。该研究有助于更深入了解酱香型白酒堆积环境的作用。

延时厌氧调控DPAOs内碳源转化实现反硝化除磷

采用SBR反应器,以模拟市政污水为进水基质,在富集PAOs后采用厌氧/缺氧/好氧运行方式富集DPAOs,探讨延长厌氧时间过程中DPAOs内碳源利用、脱氮除磷效果及富集程度.结果表明:厌氧时间由50min延长至70和90min,DPAOs内碳源的储量及利用率增加,延时厌氧条件的改进使DPAOs富集程度增加.厌氧90min COD和TP的平均去除率分别为91.54%和94.6%,DPAOs/PAOs及DPAOs对内碳源贡献率达69.4%和60.1%,继续延长厌氧时间至110和130min后,DPAOs内碳源的储量降低系统除磷效率下降,厌氧130min TP平均去除率、DPAOs/PAOs及DPAOs对内碳源贡献率分别降至84.6%、50.2%和36.4%.延时厌氧运行过程中,LB-EPS含量变化较小,内碳源储量的改变对TB-EPS影响较大.微生物群落结构分析表明,系统内优势菌门为拟杆菌门(Bacteroidetes)、变形菌门(Proteobacteria)和绿弯菌门(Chloroflexi).厌氧90min时以Dechloromonas、Candidatus_Accumulibacter为代表的DPAOs是系统内优势微生物(相对丰度由接种污泥1.44%、2.12%增至15.58%、5.86%);厌氧130min时DPAOs丰度减少,以Candidatus_Competibacter为代表的DGAOs明显增多(相对丰度由厌氧90min的3.29%增至16.16%),导致系统除磷性能下降.

不同钙源对微生物自修复混凝土裂缝的修复效果及其机理分析

本研究在模拟裂缝区溶液中,研究了不同钙源下溶液中的Ca^(2+)浓度和钙沉淀能力的变化。制备了微生物自修复砂浆试件,研究含不同钙源的微生物修复剂对砂浆试件强度的影响;以面积修复率和吸水率来评价0.25~0.40 mm裂缝的自修复效果,并研究了裂缝的修复方向。此外,通过扫描电镜和X射线衍射仪分析了砂浆试件裂缝区的修复产物,并详细探讨了不同钙源对砂浆裂缝的自修复机理。研究结果表明,在不同钙源下,枯草芽孢杆菌的矿化机理是不同的,造成了溶液中Ca^(2+)浓度和钙沉淀能力的差异,并且钙源也会影响微生物自修复砂浆的抗折抗压强度。当钙源为乳酸钙时,砂浆裂缝的修复效果最好,其次是醋酸钙和硝酸钙。在裂缝修复过程中,修复产物从裂缝表面往裂缝内部生成,因而随着裂缝深度的增加,修复产物的生成量逐渐降低,并且砂浆试件裂缝处的白色物质主要是方解石碳酸钙。本研究证明了微生物诱导碳酸钙沉积(MICP)技术可以较好地应用于水泥基材料裂缝的自修复,有利于推动微生物自修复混凝土的发展与进步。

碳源种类对生物除磷颗粒污泥效能及微生物群落特征的影响

碳源种类对污水生物除磷过程发挥重要作用,然而碳源种类对生物除磷好氧颗粒污泥(AGS)的效能及微生物群落结构的影响至今不明确。因此,本工作在中温条件下探究了碳源种类(乙酸、丙酸及两者混合)对生物除磷AGS的影响。结果表明混合碳源利于AGS对污染物及营养盐的去除。混合碳源组别COD和磷酸盐去除效率分别高达95.9%~97.8%和96.8%~98.5%。混合碳源提高了AGS浓度,促进了胞外聚合物的分泌,并提高各层EPS含量。混合碳源降低了污泥体积指数,提高了污泥沉降性。胞内聚合物分析表明混合碳源提高了聚羟基脂肪酸酯(PHA)的含量但降低了糖原质含量。微生物群落分析表明混合碳源组别内微生物丰富度和多样性均高于单一碳源,且混合碳源组别内,属水平上Candidatus Accumulibacter、Acinetobacter的相对丰度高于其他组。研究结果为生物除磷AGS的高效处理混合碳源废水提供一定的数据支撑和理论依据。

李渡特香型大曲层次间微生物群落结构与风味物质变化规律研究

目前对于特香型大曲不同层次间微生物群落结构和数量变化特征,及其与风味物质的关联性尚不清晰。该研究运用绝对定量和相对定量扩增子测序技术,揭示特香型大曲不同层次结构的微生物组成及变化规律,并对主要细菌和真菌的来源进行了溯源分析。同时运用顶空固相微萃取-气相色谱质谱联用技术(headspace solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS),比较分析大曲不同层次的风味化合物含量。结果表明,曲心的细菌总生物量显著低于曲皮和中层,为曲皮的55%,中层的53%。魏斯氏菌属(Weissella)、乳杆菌属(Lactobacillus)和肠杆菌属(Enterobacter)为曲皮的主要细菌类型,高温放线菌属(Thermoactinomyces)为曲心的特征优势细菌,而糖多孢菌属(Saccharopolyspora)在中层和曲心含量远高于曲皮。伊萨酵母属(Issatchenkia)和丝孢毕赤酵母属(Hyphopichia)为曲皮的主要酵母,曲霉属(Aspergillus)为曲心的优势霉菌。曲心的醇类、醛酮类、吡嗪类和醚酚类的总含量均高于曲皮和中层,而曲皮的酯类的总含量高于曲心。该项研究结果为优化特香型大曲制曲工艺,进而运用生态发酵技术提升大曲品质提供了重要参考。