Extracellular Enzyme Activity of Sclerotia-forming and Non-Sclerotia-forming Morchella Strains

The extracellular enzyme activities of sclerotia-forming and nonsclerotia- forming single spore strains of Morchella conica and M. crasspies were determined and compared. The non sclerotia-forming strains of M. conica exhibited higher aver- age activities of protease, catalase and xylanase but lower laccase activity than those of sclerotia-forming strains. However, the differences did not reach significance level. The soluble amylases activity of M. crasspies was significantly higher than that of M. conica, while the mean activity of other enzymes had differences between them, but the differences did not reach significance level.

Interactions of Marsh Orchid(Dactylorhiza spp.)and Soil Microorganisms in Relation to Extracellular Enzyme Activities in a Peat Soil

The nature of the interactions between microbes and roots of plants in a peaty soil were studied in a laboratory- based experiment by measuring activities ofβ-glucosidase,phosphatase,N-acetylglucosaminidase,and arylsulphatase.The experiment was based on control(autoclaved),bacteria-inoculated,and plant(transplanted with Dactylorhiza)treatments, and samples were collected over 4 sampling intervals.Higher enzyme activities were associated with the bacteria-inoculated treatment,suggesting that soil enzyme activities are mainly of microbial origin.For example,β-glucosidase activity varied between 25-30μmol g^(-1)min^(-1)in the bacteria-inoculated samples whilst the activity of the control ranged between 4-12μmol g^(-1)min^(-1)A similar pattern was found for all other enzymes. At the end of the incubation,the microcosms were destructively sampled and the enzyme activities determined in bulk soil,rhizospheric soil,and on the root surface.Detailed measurement in different fractions of the peat indicated that higher activities were found in rhizosphere.However,the higher activities ofβ-glucosidase,N-acetylglucosaminidase,and arylsulphatase appeared to be associated with bacterial proliferation on the root surface,whilst a larger proportion of phosphatase appeared to be released from root surface.

In vitro and comparative study on the extracellular enzyme activity of molds isolated from keratomycosis and soil

AIMTo isolate and identify the molds involved in mycotic keratitis; to isolate corresponding species from soil samples; to compare the extracellular enzyme activity indices of the molds isolated from keratitis cases and the corresponding soil isolates.

Season-dependence of soil extracellular enzyme activities in a Pinus koraiensis forest on Changbai Mountain

Changbai Mountain,central in the distribution of Pinus koraiensis,supports a virgin Korean pine forest with vertical gradient distribution.Soil extracellular enzyme activity(EEA) and enzyme stoichiometry(ES) are reliable indicators of the energy and nutrients utilized by microbial communities and of soil nutrient changes.We measured four representative soil EEAs(sucrase,cellulase,urease,acid phosphatase) at two soil layers(A:0-5 cm and B:5-10 cm)beneath Korean pine forest at five elevations on Changbai Mountain during growing season.The vertical and seasonal variations of EEAs were analyzed by soil enzyme stoichiometry to quantify the role of soil microorganism in the nutrient cycling process.The activities of four soil extracellular enzymes and the ratios of enzyme activity to soil microbial biomass carbon(EA/SMBC) did not vary with elevation.The first partition point of multiple regression trees was in September,and the second branch was split by elevation.Seasonal change had more influence on soil enzyme activity(A layer:75.6%;B layer:71.3%) than did change in elevation(A layer:7.8%;B layer:7.5%).Over one entire growing season,both vector length and vector angle were unchanged by elevation,but varied significantly by month.Among the soil physicochemical factors,available phosphorus and pH were the main factors affecting the four soil EE As.The ratio of basal area of the coniferous tree to broad-leaved tree species(S_(con)/S_(br)),soil microbial biomass carbon(MBC) and nitrogen(MBN) influenced the four soil EE As.The results of vector analysis revealed that C and N sources were generally sufficient,but P was limiting(vector angle> 45°).The vector angle for September was significantly higher than for other months.This result verified that phosphorus was the limiting factor affecting soil microorganism function in nutrient metabolism and cycling.Soil enzyme stoichiometry proved to be an efficient index for quantifying soil microorganismmediated nutrient cycling in the Korean pine ecosystem.

Comparative Study on Population Ecological Distribution and Extracellular Enzyme Activities of Endophytic Fungi in <i>Artemisia annua</i>

The endophytic fungi in different tissues of Artemisia annua was isolated and purified to explore their ecological distribution and tissue preference, and the extracellular enzyme activities of dominant endophytic fungi were determined to characterize the metabolic function of endophytic fungi. The results showed that a total of 67 endophytic fungi were obtained from Artemisia annua tissues. The number and species of endophytic fungi in different tissues were significantly different. The number, colonization rate (CR) and isolation rate (IR) of endophytic fungi in root were significantly higher than those of stem and leaf. The dominant endophytic fungi, diversity and similarity coefficient of endophytic fungi also showed significant difference among tissues. The extracellular enzyme activities of endophytic fungi in different tissues are significantly different. The enzyme activities of endophytic fungi isolated from root are significantly higher than those isolated from stem and leaf. The research results showed that the endophytic fungi in Artemisia annua had significant tissue preference, and the metabolic function of endophytic fungi showed significant difference among tissues. This will lay a foundation for further research, development and utilization of endophytic fungi, and also provide a theoretical basis for screening functional endophytic fungi in Artemisia annua.

Biodegradation and detoxification of the triphenylmethane dye coomassie brilliant blue by the extracellular enzymes from mycelia of Lactarius deliciosus

Fungi play an important role in dying wastewater treatment.In this work,the mycelia of Lactarius deliciosus exhibited an excellent capacity in decolorizing coomassie brilliant blue(CBB).The results demonstrated that the mycelia could treat CBB with high concentrations over a broad range of pH and temperature.The decolorization rate of 99.19%and the removal rate of 16.31 mg·L^(‒1)·h were realized.The mycelia could be recycled from decolorizing process for 19 times,indicating a good re-usability.It verified that the lignin peroxidase(121.65 U·L^(‒1))and manganese peroxidase(36.77 U·L^(‒1))were involved in the degradation and decolorization process of CBB.Toxicity assessments indicated the seed germination rate was up to 82.22%while inhibition to Escherichia coli decreased dramatically and no significant effect on Caenorhabditis elegans growth was found.The removal of CBB was a synergistic process accomplished by adsorption and biodegradation.The mycelia could be used for eco-friendly CBB treatment.

Effect of Lanthanum on Growth and Extracellular Enzyme Acitivty of Erwinia Chrysanthemi in vitro

The effect of lanthanum on the growth and extracellular enzyme activity of Erwinia chrysanthemi(Ech) was studied. Lanthanum inhibited the growth of Ech in solid culture at the concentration of 50, 100, 150, 200, 250, 300 and 350 mgL-1, and the inhibition increased with the increase of the RE concentration. The formation of colony delayed and the diameter of colony decreased. Lanthanum stimulated the growth of Ech within 24h when the lanthanum concentration was less than 200 mgL-1 in liquid medium, but significantly inhibited the growth of Ech with the increase of lanthanum concentration and culture time. When the concentration was higher than 350 mgL-1, the growth of Ech was inhibited completely both in solid and liquid culture. The extracellular enzyme acitivity of Ech was affected by lanthanum at 200 mgL-1. The activity of cellulose was promoted more than that of protease but the activity of pectinase was decreased. The maceration to potato tuber tissue decreased when the cell free filtrate was tr

Trade-off between microbial carbon use efficiency and specific nutrient-acquiring extracellular enzyme activities under reduced oxygen

Mangroves are one of the most ecologically sensitive ecosystems to global climate change,which have cascading impacts on soil carbon(C),nitrogen(N)and phosphorus(P)cycling.Moreover,mangroves are experiencing increasing N and P loadings and reduced oxygen availability due to intensified climate change and human activities.However,both direct and interactive effects of these perturbations on microbially mediated soil C,N and P cycling are poorly understood.Here,we simultaneously investigated the effects of N and P loadings and reduced oxygen on microbial biomass,microbial respiration,and extracellular enzyme activities(EEAs)in mangrove soils.We calculated the microbial metabolic quotient(qCO_(2)),which is regarded as a useful inverse metric of microbial C use efficiency(CUE).Our results show that reduced oxygen significantly increases both qCO_(2) and microbial specific EEAs(enzyme activity per unit of microbial biomass)for C-,N-and P-acquisition regardless of N or P loadings.Furthermore,we found that qCO_(2) positively correlated with microbial specific EEAs under reduced oxygen,whereas no clear relationship was detected under ambient oxygen.These results suggest that reduced oxygen increases microbial specific EEAs at the expense of increasing microbial respiration per unit biomass,indicating higher energy cost per unit enzyme production.

Expression of Extracellular Signal-regulated Kinase and Angiotensin-converting Enzyme in Human Atria during Atrial Fibrillation

In order to investigate the changes in the expression of extracellular signal regulated kinase (ERK1/ERK2) and angiotensin converting enzyme (ACE) in the patients with atrial fibrillation (AF), 52 patients with rheumatic heart diseases were examined. Nineteen patients had chronic persistent AF (AF≥6 months, CAF), 12 patients had paroxymal AF (PAF) and 21 patients had no history of AF. The ERK expression was detected at the mRNA level by reverse transcription polymerase chain reaction, at the protein level by Western blotting and at atrial tissue level by immunohistochemistry. ERK activating kinases (MEK1/2) and ACE were determined by Western blotting techniques. The expression of ERK2 mRNA was increased in the patients with CAF (74±19 U vs sinus rhythm: 32±24 U, P <0.05). Activated ERK1/ERK2 and MEK1/2 were increased to more than 150 % in the patients with AF compared to those with sinus rhythm. No significant difference between CAF and PAF was found. The expression of ACE was three fold increased in the patients with CAF compared to those with sinus rhythm. Patients with AF showed an increased expression of ERK1/ERK2 in atrial interstitial cells and marked atrial fibrosis. An ACE dependent increase in the amounts of activated ERK1/ERK2 in atrial interstitial cells may be one of molecular mechanisms for the development of atrial fibrosis in the patients with AF. These findings may have important impact on the treatment of AF.

Sponge-associated bacteria of Lakshadweep coral reefs, India: resource for extracellular hydrolytic enzymes

Sponges (Phylum: Porifera) is one of the major groups in the Lakshadweep coral reefs. These sponges harbor diverse bacteria with metabolic potentiality. From biodiversity to biotechnological prospecting, scientific investigations related to sponge associated microorganisms have expanded, but remain rather limited to few geographic locations. In this study, culturable bacteria associated with two demosponges viz Dysidea granulosa, Sigmadocia fibulata and the ambient water were screened for commercially important enzymes such as amylase, protease, gelatinase, lipase, deoxyribonucleic, phosphatase and urease. Amylase and phosphatase were the predominant enzymes produced by >80% of sponge-associated bacteria compared to the ambient water. Nearly 50% of the sponge-associated bacteria expressed multiple enzymatic activities (> 4) with variation in the percentage of expression of individual enzymes. More than 65% of the culturable heterotrophic bacteria associated with sponges were Gammaproteobacteria. The order Vibrionales was the main source for multiple enzyme production. Sponge associated bacteria formed more closely related clusters than the water isolates based upon their activity pattern. High recovery of sponge-associated bacteria with multiple enzymatic activities suggest that these versatile bacteria are yet unexploited potential for bioprospecting.

Integrated management of crop residue and nutrient enhances new carbon formation by regulating microbial taxa and enzymes

Although returning crop residue to fields is a recommended measure for improving soil carbon(C)stocks in agroecosystems,the response of newly formed soil C(NFC)to the integrated supply of residue and nutrients and the microbial mechanisms involved in NFC are not fully understood.Therefore,an 84-day incubation experiment was conducted to ascertain the microbial mechanisms that underpin the NFC response to inputs of residue and nitrogen(N),phosphorus(P),and sulfur(S)in two black(Phaeozem)soils from experimental plots at Gongzhuling,Jilin Province and Hailun,Heilongjiang Province,China.The results showed that adding residue alone accelerated microbial nutrient mining,which was supported by decreases of 8^(-1)6%in the ratios of C:N and C:P enzyme activities,relative to soils with nutrient inputs.The NFC amounts increased from 1156 to 1722 mg kg^(−1) in Gongzhuling soil and from 725 to 1067 mg kg^(−1) in Hailun soil as the levels of nutrient supplementation increased.Boosted regression tree analysis suggested thatβ-glucosidase(BG),acid phosphatase(AP),microbial biomass C(MBC),and Acidobacteria accounted for 27.8,18.5,14.7,and 8.1%,respectively,of the NFC in Gongzhuling soil and for 25.9,29.5,10.1,and 13.9%,respectively,of the NFC in Hailun soil.Path analysis determined that Acidobacteria positively influenced NFC both directly and indirectly by regulating BG,AP,and MBC,in which MBC acquisition was regulated more by AP.The amount of NFC was lower in Hailun soil than in Gongzhuling soil and was directly affected by AP,indicating the importance of soil properties such as SOC and pH in determining NFC.Overall,our results reveal the response of NFC to supplementation by N,P,and S,which depends on Acidobacteria and Proteobacteria,and their investment in BG and AP in residue-amended soil.

Enzyme extraction by ultrasound from sludge flocs

Enzymes play essential roles in the biological processes of sludge treatment. In this article, the ultrasound method to extract enzymes from sludge flocs was presented. Results showed that using ultrasound method at 20 kHz could extract more types of enzymes than that at 40 kHz and ethylenediamine tetraacetic acid （EDTA） methods. The optimum parameters of ultrasound extraction at 20 kHz were duration of 10 min and intensity of 552 W/g TSS. Under the optimum condition, ultrasound could break the cells and extract both the extracellular and a small part of intercellular enzymes. Ultrasound intensity was apparently more susceptive to enzyme extraction than duration, suggesting that the control of intensity during ultrasound extraction was more important than that of duration. The Pearson correlation analysis between enzyme activities and cation contents revealed that the different types of enzymes had distinct cation binding characteristics.

Construction of Hybrid Enzyme from HEC-SOD and Cu,Zn-SOD

Human extracellular superoxide dismutase(hEC-SOD) is a secreted tetrameric protein involved in the protection of a human body from oxygen free radicals. Its three-dimensional structure has not been confirmed. hEC-SOD couldn′t be expressed in E.coli. We constructed a hybrid enzyme, which comprises the N-terminal and C-terminal domains from hEC-SOD, fused it to human Cu,Zn-SOD. The hybrid enzyme is expressed successfully in E.coli. Further, we analyzed the expression of hEC-SOD in E.coli by mRNA differential displaying.

Cold exposure and capsaicin promote 1,2-dimethylhyrazine-induced colon carcinogenesis in rats correlates with extracellular matrix remodeling

BACKGROUND Extracellular matrix(ECM)remodeling and stiffening,which are correlated with tumor malignancy,drives tumor development.However,the relationship between ECM remodeling and rat experimental model of 1,2-dimethylhyrazine(DMH)-induced colorectal cancer(CRC)imposed by cold and capsaicin exposure remains unclear.AIM To explore the effects of cold exposure and capsaicin on ECM remodeling and ECM enzymes in DMH-induced CRC.METHODS For histopathological analysis,the sections of colon tissues were stained with hematoxylin and eosin,Masson’s trichrome,Picrosirius red,and Weigert’s Resorcin-Fuchsin to observe the remodeling of collagen and elastin.Additionally,the protein expression level of type I collagen(COL I),type 3 collagen(COL III0,elastin,matrix metalloproteinase(MMP)1,MMP2,MMP9,and tissue-specific matrix metalloproteinase 1(TIMP1)was assessed by immunohistochemistry.The messenger RNA(mRNA)levels of COL I,COL III,elastin,and lysyl oxidase-like-2(LOXL2)in the colon tissues of rats was measured by reverse-transcriptase quantitative polymerase chain reaction.RESULTS Although no differences were observed in the proportion of adenomas,a trend towards the increase of invasive tumors was observed in the cold and capsaicin group.The cold exposure group had a metastasis rate compared with the other groups.Additionally,abnormal accumulation of both collagen and elastin was observed in the cold exposure and capsaicin group.Specifically,collagen quantitative analysis showed increased length,width,angle,and straightness compared with the DMH group.Collagen deposition and straightness were significantly increased in the cold exposure group compared with the capsaicin group.Cold exposure and capsaicin significantly increased the protein levels of COL I,elastin,and LOXL2 along with increases in their mRNA levels in the colon tissues compared with the DMH group,while COL III did not show a significant difference.Furthermore,in immunohistochemical evaluations,MMP1,MMP2,MMP9,and TIMP1 staining increased in the cold exposure and capsaicin group compared with the DMH group.CONCLUSION These results suggest that chronic cold and capsaicin exposure further increased the deposition of collagen and elastin in the colonic tissue.Increased COL I and elastin mRNA and protein levels expression may account for the enhanced ECM remodel and stiffness variations of colon tissue.The upregulated expression of the LOXL2 and physiological imbalance between MMP/TIMP activation and deactivation could contribute to the progression of the CRC resulting from cold and capsaicin exposure.

Actinomycetes from Soil of Lachung, a Pristine High Altitude Region of Sikkim Himalaya, Their Antimicrobial Potentiality and Production of Industrially Important Enzymes

Investigations on actinomycetes are profoundly significant area of research since they form major resource for bioactive compounds, antimicrobials, anticancer agents, immunosuppressants, and biological control agents. A total of 59 actinomycetes were isolated from the soil sample collected from Domang, Lachung, North Sikkim, Sikkim, India. Out of the total isolates, 26 isolates with unique and distinct characteristic features were selected and analysed for antimicrobial activity as well as extracellular enzyme production. Out of 26 isolates, 17 (66%) isolates exhibited different level of growth inhibition against the test microorganism. 12 (47%) isolates showed antifungal activity and six (23%) isolates showed antibacterial activity. Most of the isolates showed antifungal activity. Isolate RCS260 was found to exhibit maximum growth inhibition (60%) against Colletotrichum gloeosporioides MTCC 8021. Isolate RCS252 showed maximum growth inhibition (67%) against Bacillus subtilis MTCC 441. Out of 26 isolates, 14 (54%) isolates exhibited chitinase activity, 25 (96%) isolates showed cellulase production, 20 (77%) isolates produced amylase enzyme and 17 (65%) isolates showed positive for protease activity. Potential isolate RCS260 has been characterized and identified as Streptomyces vinaceus strain RCS260 while isolate RCS252 was identified as Kitasatospora aburavienis strain RCS252. The antagonistic profile of strain RCS260 highlights its potential as antifungal agent against phytopathogens.

贝莱斯芽孢杆菌SF18-3的鉴定及对辣椒细菌性斑点病的防效评价

近年辽宁地区辣椒细菌性斑点病[Xanthomonas campestris pv.vesicatoria(Doidge)Dye]发生严重,为挖掘新的优质高效生防资源,以辣椒细菌性斑点病菌BWB3为靶标,采用稀释平板涂布法从动物粪肥混合物中分离获得1株高效生防细菌SF18-3。为进一步明确SF18-3的生防潜力,利用抑菌圈法优化最佳发酵条件后,采用双抗体夹心法测定其发酵液中6种胞外酶活性,测定其室内抑菌活性并评价田间盆栽防治效果,并通过形态特征观察、生理生化试验与16S rDNA序列分析确定其分类地位。结果表明:以NB为基础培养基140 r·min^(-1)恒温30℃发酵84 h后SF18-3抑菌效果最好,发酵液中蛋白酶活性与木聚糖酶活性较高,分别为536.13 U·L^(-1)与564.22 U·L^(-1);最佳发酵条件下平板抑菌圈直径为3.40 cm,盆栽防治效果达70.17%;显微镜观察SF18-3菌体呈杆状、有芽孢;革兰氏染色为阳性。16Sr DNA序列与已知贝莱斯芽孢杆菌(Bacillus velezensis)OK169608及(B.velezensis)OK147645聚为一类,结合其菌落形态与生理生化特征,确定菌株SF18-3为贝莱斯芽孢杆菌(Bacillus velezensis)。

不同生长阶段香菇栽培料木质纤维素降解利用研究

为深入了解香菇生长发育过程中栽培料木质纤维素的变化,对不同生长阶段香菇栽培料中木质纤维素含量及其相关降解酶活性进行了测定,利用傅里叶变换红外光谱(FTIR)、X-射线衍射法(XRD)和显微镜观察研究了木质纤维素微观结构分子基团、纤维素相对结晶度(CrI)和纤维表面形态的变化。结果表明,在香菇生长发育过程中,栽培料中的纤维素、半纤维素和木质素含量显著下降,木质纤维素含量(w,后同)由85.27%降低至52.23%,其与相应的降解酶系活性负相关,木质纤维素降解与纤维破坏程度呈现一定的相关性。FTIR结果显示,不同生长阶段香菇栽培料中木质纤维素特征官能团峰值发生变化,木质素降解速率高于半纤维素、低于纤维素。随着香菇的生长发育,栽培料中CrI显著降低,纤维素晶体结构受到了一定程度的破坏。结果表明,香菇首先利用栽培料中非木质纤维素组分供菌丝生长,同时分泌胞外降解酶破坏纤维结构,将大分子组分降解为小分子组分,从而满足其生长所需,高木质纤维素降解酶活性对应高木质纤维素降解率。该研究结果可为促进香菇栽培料中木质纤维素的降解利用提供依据。

Effects of long-term partial substitution of inorganic fertilizer with pig manure and/or straw on nitrogen fractions and microbiological properties in greenhouse vegetable soils

Partial substitution of inorganic fertilizers with organic amendments is an important agricultural management practice.An 11-year field experiment(22 cropping periods)was carried out to analyze the impacts of different partial substitution treatments on crop yields and the transformation of nitrogen fractions in greenhouse vegetable soil.Four treatments with equal N,P_(2)O_(5),and K_(2)O inputs were selected,including complete inorganic fertilizer N(CN),50%inorganic fertilizer N plus 50%pig manure N(CPN),50%inorganic fertilizer N plus 25%pig manure N and 25%corn straw N(CPSN),and 50%inorganic fertilizer N plus 50%corn straw N(CSN).Organic substitution treatments tended to increase crop yields since the 6th cropping period compared to the CN treatment.From the 8th to the 22nd cropping periods,the highest yields were observed in the CPSN treatment where yields were 7.5-11.1%greater than in CN treatment.After 11-year fertilization,compared to CN,organic substitution treatments significantly increased the concentrations of NO_(3)^(-)-N,NH_(4)^(+)-N,acid hydrolysis ammonium-N(AHAN),amino acid-N(AAN),amino sugar-N(ASN),and acid hydrolysis unknown-N(AHUN)in soil by 45.0-69.4,32.8-58.1,49.3-66.6,62.0-69.5,34.5-100.3,and 109.2-172.9%,respectively.Redundancy analysis indicated that soil C/N and OC concentration significantly affected the distribution of N fractions.The highest concentrations of NO_(3)^(-)-N,AHAN,AAN,AHUN were found in the CPSN treatment.Organic substitution treatments increased the activities ofβ-glucosidase,β-cellobiosidase,N-acetyl-glucosamidase,L-aminopeptidase,and phosphatase in the soil.Organic substitution treatments reduced vector length and increased vector angle,indicating alleviation of constraints of C and N on soil microorganisms.Organic substitution treatments increased the total concentrations of phospholipid fatty acids(PLFAs)in the soil by 109.9-205.3%,and increased the relative abundance of G^(+)bacteria and fungi taxa,but decreased the relative abundance of G-bacteria,total bacteria,and actinomycetes.Overall,long-term organic substitution management increased soil OC concentration,C/N,and the microbial population,the latter in turn positively influenced soil enzyme activity.Enhanced microorganism numbers and enzyme activity enhanced soil N sequestration by transforming inorganic N to acid hydrolysis-N(AHN),and enhanced soil N supply capacity by activating non-acid hydrolysis-N(NAHN)to AHN,thus improving vegetable yield.Application of inorganic fertilizer,manure,and straw was a more effective fertilization model for achieving sustainable greenhouse vegetable production than application of inorganic fertilizer alone.

蛹虫草菌株胞外发酵液抗氧化能力评价及优良菌株筛选

为建立高抗氧化能力的蛹虫草优良菌株评价筛选方法,以蛹虫草(Cordyceps militaris)胞外发酵液为研究对象,采用相关性分析对10株蛹虫草菌株进行抗氧化能力评价及优良菌株筛选。以菌株生长活性、胞外酶活力、抗氧化能力为指标,在相关性分析、隶属函数赋值计算的基础上建立线性回归方程,得到蛹虫草菌株抗氧化综合能力与发酵生物量、菌丝平均生长速度、β-葡萄糖苷酶活力、蛋白酶活力的蛹虫草菌株定向筛选模型,采用模型筛选得到优势菌株CH-1及CA-1。通过结实性实验进一步验证,蛹虫草菌株CH-1与CA-1生物学转化率可达90%以上,其虫草素含量较野生菌株高60%左右,菌株生长周期短10 d以上,试验结果说明此模型可用来快速筛选出具有高抗氧化能力的蛹虫草优良菌株。

秸秆全量还田下施氮量对秸秆降解及相关胞外酶活性的影响

该试验采用尼龙网袋原位培养法,研究了冷凉区稻田秸秆全量还田下不同施氮水平(110、120、130、140、150 kg·hm^(-2))的水稻秸秆降解特征以及相关胞外酶活性变化特征。结果表明:在秸秆全量还田但施氮量不同的条件下,水稻秸秆在还田前期(0~20 d)和中后期(71~104 d)的降解率较快,此时秸秆残余物中可溶物质的占比大幅度减少,木质素等物质含量在秸秆残余物中的占比增加;在东北冷凉区水稻生育期内,0~15㎝还田秸秆平均降解率约为55%,15~30㎝还田秸秆平均降解率约为50%;与碳相关胞外酶(αG、βG、CBH、βX)活性普遍高于其他功能胞外酶,且秸秆降解胞外酶活性普遍在中后期(71~104 d)升高。研究表明东北冷凉区水稻秸秆全量条件下,施氮量140kg·hm^(-2)时秸秆降解率的综合效应最好,最佳秸秆还田深度为0~15 cm。