土霉素降解菌筛选及降解特性研究

【目的】近年来,抗生素在畜禽及水产养殖中的使用量增加,导致固体废弃物和污水中存在大量的抗生素和耐药菌。土霉素作为用于养殖业主要的抗生素之一,在畜禽粪便和污水中的残留含量较高,因此,筛选并鉴定了能降解残留土霉素的微生物。【方法】采用富集驯化法,以菌肥、药渣和畜禽粪便为原料,采用摇床震荡的方法进行微生物培养,采用高效液相色谱法(HPLC)进行土霉素含量测定,筛选出能够高效降解土霉素的微生物。本研究还对降解菌在不同温度、p H、转速和接种量条件下的土霉素降解效果进行优化,并最终利用16S r DNA的方法鉴定菌种。【结果】筛选出一株能够高效降解土霉素的菌株T4菌,经16S r DNA测序鉴定该菌株为假单胞菌(Pseudomonas sp.),该菌株在30℃时对土霉素的降解率最高,达到了26.75%;不同p H梯度下,T4菌在p H为7时对土霉素的降解率达到最高,为27.03%;转速为150 rpm和170 rpm时,T4菌对土霉素的降解率分别为26.18%和25.59%,考虑到摇床高转速耗能高的因素,因此选择150 rpm为优化的转速;接种量对T4菌降解土霉素的影响较小,而且二者之间呈负相关,接种量1%时降解率最高,为26.88%。优化条件下,T4菌对100 mg/L土霉素的降解率为26.29%;堆肥试验表明,添加了T4菌之后,土霉素去除率更高,为93.21%。【结论】本研究筛选出的菌株T4对土霉素有较好的降解能力。通过16S r DNA基因序列分析,T4菌属于假单胞菌(Pseudomonas sp.),其降解土霉素的优化条件为温度30℃、p H 7.0、转速150 rpm、接种量1%。在堆肥中接种T4菌后,提高了对土霉素的去除作用,表明T4菌作为土霉素降解菌具有污染治理的潜力。

猪场粪污源大量元素水溶肥料在叶菜上的肥效研究

为研究一种以猪场粪污为原料的新型大量元素(含微量元素Cu)水溶肥料的应用效果,采用田间小区试验,通过设置清水对照、等养分单质肥料和猪场粪污源大量元素水溶肥料3个处理,研究施用供试大量元素(含微量元素Cu)水溶肥料对不同试验点叶菜产量、叶绿素和Vc含量的影响。结果表明:施用猪场粪污源大量元素(含微量元素Cu)水溶肥料增加了叶菜的产量、叶绿素和Vc含量,与清水对照相比,叶菜产量增产幅度为5. 50%～41. 43%,叶绿素和Vc含量分别提高5. 59%～24. 53%和7. 14%～35. 71%;与等养分单质肥料相比,叶菜产量增产达6. 64%～19. 16%,叶绿素和Vc含量分别提高1. 93%～13. 96%和6. 52%～26. 67%。可见,该新型大量元素(含微量元素Cu)水溶肥料的施用可以有效提高叶菜产量,并改善其品质,值得推广应用。

Uptake and translocation of organic pollutants in plants:A review

Organic pollutants, such as polychlorinated dJbenzo-p-dioxins and polychlofinated dibenzofurans （PCDD/Fs）, polychlodnated biphenyls （PCBs）, antibiotics, herbicides, and bisphenol A （BPA）, are commonly found in agricultural environments. They are released into the environment as a result of their use for human health purposes and farm management activities, and are often discharged as waste-water effluents. Most of these organic pollutants are taken up by plants through roots and leaves, and when they enter the tissue, they cause serious damage to the plants. Although the toxicity of organic pollutants to plants, especially to plant cells, has been intensively studied, a systematic review of these studies is lacking. Here we review researches on the toxicity of organic pollutants, their uptake, and translocation in plants. Our objective is to assemble existing knowledge concerning the interaction of organic pollutants with plants, which should be useful for the development of plant-based systems for removing pollutants from aquatic and agricultural environments.

Degradation mechanisms of oxytetracycline in the environment

Over the past few decades,the usage of oxytetracycline(OTC),a kind of antibiotic,has increased with the development of aquaculture and livestock breeding.However,about 30–90%of the applied antibiotics are excreted as the parent compounds into the environment,especially with the application of animal manure to agricultural fields.This large influx of antibiotics may lead to the destruction of the natural microbial ecological community and pose great threats to human beings through the food chain.Therefore,the fate and toxicity of OTC in the environment are issues of great concern.Degradation of OTC,including the non-biodegradation and biodegradation,and the biological toxicity of its degradation products or metabolites,are reviewed in this paper.The non-biodegradation pathways include hydroxylation,quinonization,demethylation,decarbonylation,dehydration and secondary alcohol oxidation.Light(particularly UV light),pH and oxidizing substances play important roles in non-biodegradation.Biodegradation products include 4-epi-OTC(EOTC),2-acetyl-2-decarboxy-amido-OTC(ADOTC),α-apo-OTC andβ-apo-OTC.EOTC is an epimer and identied except for the configuration of the C4 dimethylamino group of OTC.Temperature and pH are the main factors affecting biodegradation pathways of OTC.In addition,this review discusses concerns over the biological toxicity of OTC degradation products.

Screening and degradation characteristics of a tylosin-degrading strain

Antibiotics residues have been accumulating in the environment day by day due to overuse of antibiotics.Recalcitrant antibiotic residues,such as tylosin(TYL),can cause serious environmental problems,which makes it important to eliminate TYL from the environment.It is important to eliminate TYL from the environment.In this study,a strain was isolated and purified from fermentation by-product that came from a TYL production factory.The TYL degrading strain was identified by its morphology,physiological and biochemical reactions and sequencing the PCR-amplified fragments of its 16 S r DNAcoding genes.The temperature,shaking speed,initial TYL concentration,p H and inoculum sizes were investigated under simulated conditions by using single factor tests.The results showed that TYL2,a high efficient strain was isolated and was identified as Brevibacillus borstelensis.The degradation rate of TYL by this strain could reach to 75%with an initial concentration of 25 mg L^-1 within 7 days under conditions of 7%B.borstelensis(v/v,2×108 CFU m L^-1)at p H 7.0 and at 35°C.It is interesting that this strain has a very strong ability to degrade the TYL in natural sewage with the degradation rate of 65%within 7 days.This result could be helpful for the degradation of TYL and provide guidance for the degradation of other antibiotics.

Microbial community dynamics during composting of animal manures contaminated with arsenic,copper,and oxytetracycline

Effects of the heavy metal copper(Cu), the metalloid arsenic(As), and the antibiotic oxytetracycline(OTC) on bacterial community structure and diversity during cow and pig manure composting were investigated. Eight treatments were applied, four to each manure type, namely cow manure with:(1) no additives(control),(2) addition of heavy metal and metalloid,(3) addition of OTC and(4) addition of OTC with heavy metal and metalloid;and pig manure with:(5) no additives(control),(6) addition of heavy metal and metalloid,(7) addition of OTC and(8) addition of OTC with heavy metal and metalloid. After 35 days of composting, according to the alpha diversity indices, the combination treatment(OTC with heavy metal and metalloid) in pig manure was less harmful to microbial diversity than the control or heavy metal and metalloid treatments. In cow manure, the treatment with heavy metal and metalloid was the most harmful to the microbial community, followed by the combination and OTC treatments. The OTC and combination treatments had negative effects on the relative abundance of microbes in cow manure composts. The dominant phyla in both manure composts included Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The microbial diversity relative abundance transformation was dependent on the composting time. Redundancy analysis(RDA) revealed that environmental parameters had the most influence on the bacterial communities. In conclusion, the composting process is the most sustainable technology for reducing heavy metal and metalloid impacts and antibiotic contamination in cow and pig manure. The physicochemical property variations in the manures had a significant effect on the microbial community during the composting process. This study provides an improved understanding of bacterial community composition and its changes during the composting process.

The impacts of oxytetracycline on humification during manure composting can be alleviated by adjusting initial moisture contents as illustrated by NMR

Oxytetracycline(OTC)residues have been found in soil and water,and they may pose potential risks to agricultural ecological environments.One of the most impactful ways for OTC to enter the soil and water environments is through excrement used as organic fertilizer.Therefore,it is important to remove OTC during manure composting and to understand the transformation of the organic materials during composting in the presence of OTC.In the present paper,chicken manure and wheat sawdust spiked with OTC were composted under different initial moisture contents(MC)to evaluate the degradation of OTC and changes of organic matter during the composting process.The MC has a significant effect on OTC degradation during composting.A higher MC of 65% was more conducive to OTC degradation(77.4%)and compost maturity compared to the lower MC.However,the higher MC of 65%could increase the ammonia volatilization by promoting nitrification compared to the lower MC.An increase in the initial MC could improve the composting temperature.NMR results illustrated that the presence of OTC could affect the internal transformation of aliphatics,and OTC inhibited compost humification.Thus,an initial MC of 55–65% can alleviate the impacts of OTC on humification during manure composting.

Prediction model for mercury transfer from soil to corn grain and its cross-species extrapolation

In this study the transfer characteristics of mercury（Hg） from a wide range of Chinese soils to corn grain（cultivar Zhengdan 958） were investigated. Prediction models were developed for determining the Hg bioconcentration factor（BCF） of Zhengdan 958 from soil, including the soil properties, such as p H, organic matter（OM） concentration, cation exchange capacity（CEC）, total nitrogen concentration（TN）, total phosphorus concentration（TP）, total potassium concentration（TK）, and total Hg concentration（THg）, using multiple stepwise regression analysis. These prediction models were applied to other non-model corn cultivars using a cross-species extrapolation approach. The results indicated that the soil p H was the most important factor associated with the transfer of Hg from soil to corn grain. Hg bioaccumulation in corn grain increased with the decreasing p H. No significant differences were found between two prediction models derived from different rates of Hg applied to the soil as HgCl2. The prediction models established in this study can be applied to other non-model corn cultivars and are useful for predicting Hg bioconcentration in corn grain and assessing the ecological risk of Hg in different soils.

尾煤泥制烧结砖可行性研究

霍州煤电集团针对生产尾煤泥外排的问题,在对其尾煤泥特性进行综合分析的基础上,实施了以尾煤泥为主要原料掺配少量煤矸石代替黏土,制烧结(内燃)砖的课题研究。并对其技术特征、烧结工艺、生产环境条件、性能指标等要点进行了反复分析研究、实验室试验及工业性试验。研究试验表明尾煤泥具有黏而细的特性,其成分与黏土相近,符合制烧结砖的基础条件。研究试制的多孔砖,抗压强度均能达到MU20,冻融、泛霜、抗石灰爆裂、吸水率、放射性等指标均能达到国家标准。