Biodegradability of 2-ethylhexyl nitrate (2-EHN), a cetane improver of diesel oil

The 2-ethyhexyl nitrate (2-EHN) is currently added to diesel oil to improve ignition and boost cetane number. The biodegradability of this widely used chemical needed to be assessed in order to evaluate the environmental impact in case of accidental release. In aerobic liquid cultures, biodegradation of 2-EHN was assessed in biphasic liquid cultures using an inert non-aqueous phase liquid such as 2,2,4,4,6,8,8-heptamethylnonane (HMN) as solvent for the hydrophobic substrate. 2-EHN was found to be biodegradable by microbial communities from refinery wastewater treatment plants, but was recalcitrant to those of urban wastewater treatment facilities. Out of eighteen hydrocarbon-polluted or non-polluted soil samples, six microbial populations were also able to degrade 2-EHN. However, strain isolation from these microbial populations was rather difficult suggesting close cooperation between members of the microbial communities. Specific axenic bacterial strains selected for their ability to catabolize recalcitrant-hydrocarbons were also tested for their capacity to degrade 2-EHN. In liquid cultures with HMN phase as non-aqueous phase liquid, some Mycobacterium austroafricanum strains were found to degrade and mineralize 2–EHN significantly.     

Anaerobic ammonium oxidation (Anammox) in immobilized activated sludge biofilms during the treatment of weak wastewater

This work studied the formation of molecular nitrogen by the microbial population of immobilized activated sludge of the domestic wastewater treatment plants (WWTP) that employ the technology developed by ZAO ECOS Company. The technology includes physicochemical water pretreatment and treated water recycling. A hard flexible fibrous brush carrier is used for the immobilization of microorganisms. The presence of both aerobic and anaerobic microorganisms and functioning of the methanogenic microbial community was shown in the biofilms developing on the carrier fibers and in suspended sludge. The high efficiency of nitrogen removal at a low C/N ratio was established to be due to the conjugated nitrification, denitrification, and anammox processes, whose functioning was demonstrated by laboratory cultivation methods and by studying the processes in batch and continuous reactors. Fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes (FISH) revealed bacteria belonging to the order Planctomycetales, particularly their anammox group. This work is the first evidence of the important role of the anammox process in the combined system of physicochemical and biological treatment of weak wastewater (BCDEAMOX).     

Aerobic degradation of phthalic acid by Comamonas acidovoran Fy-1 and dimethyl phthalate ester by two reconstituted consortia from sewage sludge at high concentrations

Microbial degradation of phthalic acid (PA) and dimethyl phthalate ester (DMPE) under aerobic conditions was investigated using a pure species of bacteria and two consortia from sewage sludge. Five morphologically distinct microorganisms were obtained in pure culture and identified, and tested for the capability of degrading phthalate and DMPE. Comamonas acidovorans strain Fy-1 showed the highest ability to degrade high concentrations of phthalate (2600 mg/l) within 48 h. Two reconstituted consortia of microorganisms, one comprising Pseudomonas fluorescens, P. aureofaciens and Sphingomonas paucimobilis, and the other of Xanthomonas maltophilia and S. paucimobilis, were effective in completely degrading DMPE (400 mg/l) in 48–96 h. The three-species consortium appeared to be more effective in the degradation of DMPE, and both consortia proceeded via formation of mono-methyl phthalate (MMP) and then phthalatic acid before mineralization. This study suggests that high concentrations of the endocrine-disrupting chemicals phthalate and DMPE can be mineralized in wastewater treatment systems by indigenous microorganisms.     

Appraising bacterial strains for rapid BOD sensing—an empirical test to identify bacterial strains capable of reliably predicting real effluent BODs

The measured response of rapid biochemical oxygen demand (BOD) biosensors is often not identical to those measured using the conventional 5-day BOD assay. This paper highlights the efficacy of using both glucose–glutamic acid (GGA) and Organisation for Economic Cooperation and Development (OECD) BOD standards as a rapid screen for microorganisms most likely to reliably predict real effluent BODs when used in rapid BOD devices. Using these two synthetic BOD standards, a microorganism was identified that produced comparable BOD response profiles for two assays, the MICREDOX® assay and the conventional 5-day BOD₅ test. A factorial experimental design systematically evaluated the impact of four factors (microbial strain, growth media composition, media strength, and microbial growth phase) on the BOD response profiles using GGA and OECD synthetic standard substrates. An outlier was identified that showed an improved correlation between the MICREDOX® BOD (BOD_sens) and BOD₅ assays for both the synthetic standards and for real wastewater samples. Microbial strain was the dominant factor influencing BOD_sens values, with Arthrobacter globiformis single cultures clearly demonstrating superior rapid BOD_sens response profiles for both synthetic and real waste samples. It was the only microorganism to approach the BOD₅ response for the OECD substrate (171 mg O₂?L^?1), and also reported BOD values for real waste samples that were comparable to those produced by the BOD₅ test, including discriminating between filtered and unfiltered samples.     

聚氨酯塑料的微生物降解

未被合理处置的废塑料污染已成为全球性的环境问题,探索塑料废弃物的无害化处理技术势在必行。近来,研究证实了自然界中存在可以降解塑料的微生物及酶。利用微生物或酶对废塑料进行生物处理成为可能。聚氨酯塑料(Polyurethane,PUR)是广泛应用的通用塑料之一,其废弃物量已占到所有废塑料总体积的30%。文中将PUR塑料发明应用70年来有关微生物降解的研究进行了全面综述,对PUR塑料降解真菌、细菌、降解基因与酶、降解产物及相关的生物处理技术系统等进行了总结与分析,并对实现PUR废塑料高效生物处理需解决的关键科学问题进行了展望。     

The Potential of Canna lily for Wastewater Treatment Under Indian Conditions

Low cost treatment of polluted wastewater has become a serious challenge in most of the urban areas of developing countries. The present study was undertaken to investigate the potential of Canna lily towards removal of carbon, nitrogen, and phosphorus from wastewater under sub-tropical conditions. A constructed wetland (CW) cell supporting vegetative layer of Canna lily was used to treat wastewater having high strength of CNP. Removal of biological oxygen demand (BOD₃) and chemical oxygen demand (COD) varied between 69.8–96.4% and 63.6–99.1%, respectively. C. lily could efficiently remove carbon from a difficult to degrade wastewater at COD:BOD ratio of 24.4. Simultaneous reduction in TKN and nitrate pointed to good nitrification rates, and efficient plant assimilation as the dominant nutrient removal mechanism in the present study. Suitable Indian agro-climatic conditions favored plant growth and no evident stress over the Canna plant was observed. High removal rate of 809.8 mg/m²-day for TKN, 15.0 mg/m²-day for nitrate, and 164.2 mg/m²-day for phosphate suggests for a possible use of Canna-based CW for wastewater treatment for small, rural, and remote Indian communities.     

Effect of Microbial Species Richness on Community Stability and Community Function in a Model Plant-Based Wastewater Processing System

Microorganisms will be an integral part of biologically based waste processing systems used for water purification or nutrient recycling on long-term space missions planned by the National Aeronautics and Space Administration. In this study, the function and stability of microbial inocula of different diversities were evaluated after inoculation into plant-based waste processing systems. The microbial inocula were from a constructed community of plant rhizosphere-associated bacteria and a complexity gradient of communities derived from industrial wastewater treatment plant-activated sludge. Community stability and community function were defined as the ability of the community to resist invasion by a competitor (Pseudomonas fluorescens 5RL) and the ability to degrade surfactant, respectively. Carbon source utilization was evaluated by measuring surfactant degradation and through Biolog and BD oxygen biosensor community level physiological profiling. Community profiles were obtained from a 16S–23S rDNA intergenic spacer region array. A wastewater treatment plant-derived community with the greatest species richness was the least susceptible to invasion and was able to degrade surfactant to a greater extent than the other complexity gradient communities. All communities resisted invasion by a competitor to a greater extent than the plant rhizosphere isolate constructed community. However, the constructed community degraded surfactant to a greater extent than any of the other communities and utilized the same number of carbon sources as many of the other communities. These results demonstrate that community function (carbon source utilization) and community stability (resistance to invasion) are a function of the structural composition of the community irrespective of species richness or functional richness.     

Safety and regulation of yeasts used for biocontrol or biopreservation in the food or feed chain

Yeasts have been important components of spontaneous fermentations in food and beverage processing for millennia. More recently, the potential of utilising antagonistic yeasts, e.g. Pichia anomala and Candida spp., for post-harvest biological control of spoilage fungi during storage of plant-derived produce (‘biopreservation’) has been clearly demonstrated. Although some yeast species are among the safest microorganisms known, several have been reported in opportunistic infections in humans, including P. anomala and bakers’ yeast, Saccharomyces cerevisiae. More research is needed about the dominant pathogenicity and virulence factors in opportunistic yeasts, and whether increased utilisation of biopreservative yeasts in general could contribute to an increased prevalence of yeast infections. The regulatory situation for yeasts used in post-harvest biocontrol is complex and the few products that have reached the market are mainly registered as biological pesticides. The qualified presumption of safety (QPS) approach to safety assessments of microorganisms intentionally added to food or feed, recently launched by the European Food Safety Authority, can lead to more efficient evaluations of new products containing microbial species with a sufficient body of knowledge or long-term experience on their safety. P. anomala is one of several yeast species that have been given QPS status, although the status is restricted to use of this yeast for enzyme and metabolite production purposes. With regard to authorisation of new biopreservative yeasts, we recommend that the possibility to regulate microorganisms for food biopreservation as food additives be considered.     

Convenient treatment of acetonitrile-containing wastes using the tandem combination of nitrile hydratase and amidase-producing microorganisms

This study aimed to construct an acetonitrile-containing waste treatment process by using nitrile-degrading microorganisms. To degrade high concentrations of acetonitrile, the microorganisms were newly acquired from soil and water samples. Although no nitrilase-producing microorganisms were found to be capable of degrading high concentrations of acetonitrile, the resting cells of Rhodococcus pyridinivorans S85-2 containing nitrile hydratase could degrade acetonitrile at concentrations as high as 6 M. In addition, an amidase-producing bacterium, Brevundimonas diminuta AM10-C-1, of which the resting cells degraded 6 M acetamide, was isolated. The combination of R. pyridinivorans S85-2 and B. diminuta AM10-C-1 was tested for the conversion of acetonitrile into acetic acid. The resting cells of B. diminuta AM10-C-1 were added after the first conversion involving R. pyridinivorans S85-2. Through this tandem process, 6 M acetonitrile was converted to acetic acid at a conversion rate of >90% in 10 h. This concise procedure will be suitable for practical use in the treatment of acetonitrile-containing wastes on-site.     

Microbial community dynamics in anaerobic bioreactors and algal tanks treating piggery wastewater

Integrated biosystem is becoming a major aspect of wastewater management practice. Microbial communities in piggery wastewater sampled from anaerobic (thermophilic and mesophilic) and aerobic digesters (algal tanks) during waste remediation were analyzed by culture-independent techniques based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The use of Muyzer's 314F-GC, 518R bacterial primers, and archaeal A934F, 1309R primers followed by partial 16s rDNA sequence analysis of the main bands from DGGE revealed the presence of unknown and as yet uncultured microorganisms but also showed functional and ecologically significant denitrifying, acetogenic bacteria along with autotrophic, hydrogenotrophic, and acetoclastic methanogen archaea. Thermophilic digesters were dominated by γ-Proteobacteria, Methanothermobacter sp., while mesophilic digesters showed dominance by Firmicutes, uncultured bacteria, Methanosarcina, and Methanoculleus genera. Under aerobic conditions within algal tanks, pH rose from 7.17 to 9.32, with a significant decrease in total ammonia nitrogen, chemical oxygen demand, and soluble phosphorus levels. PCR-DGGE proved a useful tool for investigating the dynamics of microbial community in the bio-processing of piggery wastewater. Knowledge of the microbial communities involved in digestion of piggery wastewater will allow optimization of integrated biosystem by removing the main pollutants like inorganic ammonium-nitrogen, phosphorus, and pathogens from intensive farming system.     

花生根际微生物的分离及高效功能菌株筛选

【背景】花生根际分布着丰富的微生物类群，分离筛选多种功能的高效微生物是研发高效复合菌肥的基础。【目的】从花生根际土壤及根表分离微生物，分析可培养微生物的多样性，筛选高效解有机磷和无机磷、产吲哚乙酸(indole-3-acetic acid, IAA)和铁载体功能的菌株，为研发花生微生物菌肥打下基础。【方法】利用稀释涂布法，从采自山东省栖霞市、平度市、烟台市莱山区 3个样点的花生根际土、根表样品中分离微生物，基于16S rRNA基因序列对其进行系统发育分析，并通过初筛和复筛筛选高效解磷、产IAA和铁载体的菌株。【结果】共分离、纯化、保藏147株菌，其中75株分离自根际土壤，72株分离自根表样品。系统发育分析表明所有的菌分布于放线菌门(Actinomycetota)、芽孢杆菌门(Bacillota)、拟杆菌门(Bacteroidota)和假单胞菌门(Pseudomonadota)这4个门的40个属，优势属为链霉菌属(Streptomyces, 21.77%)、芽孢杆菌属(Bacillus, 16.33%)；根表样品微生物的多样性高于根际样品；共筛选到解有机磷菌株62株，短波单胞菌(Brevundimonas) YTU21021解有机磷能力最强为1.12 mg/L；解无机磷菌株31株，不动杆菌(Acinetobacter) YTU21009解无机磷能力最强为7.04 mg/L；产IAA的菌株63株，肠杆菌(Enterobacter) YTU21054产IAA量最高，达184.19 mg/L；产铁载体细菌7株，伯克氏菌(Burkholderia) YTU21051产铁载体能力最强，A_s/A_r为0.90。【结论】花生根际和根表样品中可培养微生物多样性较为丰富，本研究筛选到的高效功能菌丰富了花生根际功能微生物资源，为后续与高效根瘤菌联合研发花生复合微生物菌肥奠定了基础。     

Degradation of Antibiotics (Tetracycline,Sulfathiazole, Ampicillin) Using Enzymes of Glutathion S-Transferase

Swine wastewater is not easily treated in biological wastewater treatment plants. One reason is that some antibiotics are not easily degradable in a normal treatment system and inhibit the biological organisms in the treatment system. Specifically, tetracycline, sulfathiazole, and ampicillin are representative antibiotics found in poultry wastewater. To degrade these refractory and impediment antibiotics more easily, a special method is needed, such as an enzyme method. This research used a special enzyme in an experiment that tested feasibility with an enzyme assay of biological treatment in vitro. The Glutathion S-Transferases (GSTs) are a family of proteins that catalyze the conjugation of reduced glutathione with a variety of hydrophobic chemicals containing electrophilic centers. Using GSTs, these major antibiotics were transformed into components that were non-toxic to the microorganisms that treat manure wastewater. The initial concentration of tetracycline, sulfathiazole, and ampicillin were 100 mg/L, 100 mg/L, and 50 mg/L, respectively, and the concentration of pig feed was the same as usual. The GSTs have made the effect of biotransformation of antibiotics as their mode. They were 60–70% transformed by GSTs at the end of the degradation reaction. This lowered their inhibitory strength against microorganisms.     

Performance Assessment of Full-Scale Wastewater Treatment Plants Based on Seasonal Variability of Microbial Communities via High-Throughput Sequencing

Microbial communities of activated sludge (AS) play a key role in the performance of wastewater treatment processes. However, seasonal variability of microbial population in varying AS-based processes has been poorly correlated with operation of full-scale wastewater treatment systems (WWTSs). In this paper, significant seasonal variability of AS microbial communities in eight WWTSs located in the city of Guangzhou were revealed in terms of 16S rRNA-based Miseq sequencing. Furthermore, variation redundancy analysis (RDA) demonstrated that the microbial community compositions closely correlated with WWTS operation parameters such as temperature, BOD, NH₄⁺-N and TN. Consequently, support vector regression models which reasonably predicted effluent BOD, SS and TN in WWTSs were established based on microbial community compositions. This work provided an alternative tool for rapid assessment on performance of full-scale wastewater treatment plants.     

Microbiological Degradation of Malodorous Substances of Swine Waste under Aerobic Conditions

Phenol, p-cresol, and volatile fatty acids (VFA; acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids) were used as odor indicators of swine waste. Aeration of the waste allowed the indigenous microorganisms to grow and degrade these malodorous substances. The time required for degradation of these substances varied according to the waste used, and it was not necessarily related to their concentrations. Using a minimal medium which contained one of the malodorous compounds as sole carbon source, we have selected from swine waste microorganisms that can grow in the medium. The majority of these microorganisms were able to degrade the same substrate when inoculated in sterilized swine waste but with an efficiency varying from one strain to the other. None of these strains was able to degrade all malodorous substances studied. Within 6 days of incubation these selected strains degraded the following: Acinetobacter calcoaceticus, phenol and all VFA; Alcaligenes faecalis, p-cresol and all VFA; Corynebacterium glutamicum and Micrococcus sp., phenol, p-cresol, and acetic and propionic acids; Arthrobacter flavescens, all VFA. On a laboratory scale, the massive inoculation of swine waste with C. glutamicum or Micrococcus sp. accelerated degradation of the malodorous substances. However, this effect was not observed with all of the various swine wastes tested. These results suggest that an efficient deodorization process of various swine wastes could be developed at the farm level based on the aerobic indigenous microflora of each waste.     

Alginate beads provide a beneficial physical barrier against native microorganisms in wastewater treated with immobilized bacteria and microalgae

When the freshwater microalga Chlorella sorokiniana and the plant growth-promoting bacterium Azospirillum brasilense were deployed as free suspensions in unsterile, municipal wastewater for tertiary wastewater treatment, their population was significantly lower compared with their populations in sterile wastewater. At the same time, the numbers of natural microfauna and wastewater bacteria increased. Immobilization of C. sorokiniana and A. brasilense in small (2–4 mm in diameter), polymer Ca-alginate beads significantly enhanced their populations when these beads were suspended in normal wastewater. All microbial populations within and on the surface of the beads were evaluated by quantitative fluorescence in situ hybridization combined with scanning electron microscopy and direct measurements. Submerging immobilizing beads in wastewater created the following sequence of events: (a) a biofilm composed of wastewater bacteria and A. brasilense was created on the surface of the beads, (b) the bead inhibited penetration of outside organisms into the beads, (c) the bead inhibited liberation of the immobilized microorganisms into the wastewater, and (d) permitted an uninterrupted reduction of ammonium and phosphorus from the wastewater. This study demonstrated that wastewater microbial populations are responsible for decreasing populations of biological agents used for wastewater treatment and immobilization in alginate beads provided a protective environment for these agents to carry out uninterrupted tertiary wastewater treatment.     

Biodegradation of p-nitrophenol by microalgae

A study was made on the use of a mixed microalgal consortium to degrade p-nitrophenol. The consortium was obtained from a microbial community in a waste container fed with the remains and by-products of medium culture containing substituted aromatic pollutants (nitrophenols, chlorophenols, fluorobenzene). After selective enrichment with p-nitrophenol (p-NP), followed by an antibiotic treatment, an axenic microalgal consortium was recovered, which was able to degrade p-nitrophenol. At a concentration of 50 mg L^–1, total degradation occurred within 5 days. Two species, Chlorella vulgaris var. vulgaris f. minuscula and Coenochloris pyrenoidosa, were isolated from the microalgal consortium. The species were able to accomplish p-NP biodegradation when cultured separately, although Coenochloris pyrenoidosa was more efficient, achieving the same degradation rate as the original axenic microalgal consortium. When Coenochloris pyrenoidosa was associated with Chlorella vulgaris in a 3:1 ratio, complete removal of the nitro-aromatic compound occurred within three days. This is apparently the first report on the degradation of a nitro-aromatic compound by microalgae.     

Immobilised activated sludge based biosensor for biochemical oxygen demand measurement

A biochemical oxygen demand (BOD) sensor, based on an immobilised mixed culture of microorganisms in combination with a dissolved oxygen electrode, has been developed for the purpose of on-line monitoring of the biological treatment process for waste and wastewater. The sensor was designed for easy replacement of the biomembrane, thereby making it suitable for short-term use. The drawbacks of activated sludge based sensor, such as short sensor lifetime, were thereby circumvented. The sensor BOD measurements were carried out in the kinetic mode using a flow injection system, resulting in 25 s for one measurement followed by 4–8 min recovery time. Based on the results of normalised sensor responses, the OECD synthetic wastewater was considered to be a more suitable calibration solution in comparison with the GGA solution. Good agreement was achieved between the results of the sensor BOD measurement and those obtained from BOD₅ analysis of a wastewater sample from a food-processing factory. Reproducibility of responses using one sensor was below ±5.6% standard deviation. Reproducibility of responses using different sensors was within acceptable bias limits, viz. ±15% standard deviation.     

奶牛粪酸臭成分降解过程中的微生物群落变化

【目的】研究可降解成年泌乳奶牛粪中主要酸臭物的微生物群落的组成及动态变化。【方法】利用牛粪堆肥环境中的微生物进行了发酵优化、菌种驯化以及酸臭有机物降解规律的研究,结合r DNA高通量测序技术对有益微生物的组成及相对生物量进行了分析。【结果】实验发现,奶牛排泄物中的臭味来源主要为短链有机酸,堆肥自然环境中的微生物可以有效地对有机酸等污染物进行去除,经从低到高浓度的有机酸臭物(W/V,0.1%–0.2%)驯化发酵后,培养物中原核微生物以芽孢杆菌居多,而真核微生物主要由红曲霉及粉状毕赤酵母组成。【结论】进一步推测这几种微生物是耐受并降解有机酸臭物的优势微生物,可以应用于奶牛养殖过程中酸臭排泄物的生物控制。     

餐厨垃圾高温好氧生物减量菌种的筛选及特性

【背景】随着餐厨垃圾产生量的逐步提高,如何实现其快速降解,成为餐厨垃圾处理亟待解决的问题。餐厨垃圾的高温好氧生物减量技术是一种可以快速降解餐厨垃圾的有效方法。【目的】筛选能够适应餐厨垃圾环境且具有高效降解餐厨垃圾中有机物能力的菌株,以提高餐厨垃圾的降解效率和减量效果。【方法】采用温度梯度耐受性实验和餐厨垃圾浸出液高油高盐耐受性实验进行菌种初筛,并利用产酶培养基复筛及餐厨垃圾生物减量实验验证。【结果】通过初筛、复筛和功能验证,最终获得4株生物减量效果优良的菌株N3-1、C7、N3-3和G6-1,其对餐厨垃圾挥发性固体(volatile solid,VS)的降解率分别为36.95%、33.23%、32.83%和31.91%,是对照组的3.02、2.71、2.68和2.61倍。经鉴定,这4株菌分别属于热嗜油地芽孢杆菌(Geobacillus thermoleovorans)、史氏芽孢杆菌(Bacillus smithii)、热解木糖地芽孢杆菌(Geobacillus caldoxylosilyticus)和立陶宛地芽孢杆菌(Geobacillus lituanicus)。【结论】筛选出的4株菌均具有较强的餐厨垃圾原料适应性和高效的生物降解能力,为开发餐厨垃圾高温好氧复合菌剂奠定了基础,并为实现餐厨垃圾减量化、无害化处理和资源化利用提供了技术支持。     

Biodegradability and biodegradation of poly(lactide)

Poly(lactide) (PLA) has been developed and made commercially available in recent years. One of the major tasks to be taken before the widespread application of PLA is the fundamental understanding of its biodegradation mechanisms. This paper provides a short overview on the biodegradability and biodegradation of PLA. Emphasis is focused mainly on microbial and enzymatic degradation. Most of the PLA-degrading microorganisms phylogenetically belong to the family of Pseudonocardiaceae and related genera such as Amycolatopsis, Lentzea, Kibdelosporangium, Streptoalloteichus, and Saccharothrix. Several proteinous materials such as silk fibroin, elastin, gelatin, and some peptides and amino acids were found to stimulate the production of enzymes from PLA-degrading microorganisms. In addition to proteinase K from Tritirachium album, subtilisin, a microbial serine protease and some mammalian serine proteases such as α-chymotrypsin, trypsin, and elastase could also degrade PLA.