Cross-linkedα-amylase aggregates on Fe3O4 magnetic nanoparticles modified with polydopamine/polyethyleneimine for efficient hydrolysis of starch

In this workα-amylase was immobilized on magnetic Fe3O4 nanoparticles with polyethylenimine(PEI)/polydopamine(PDA)coating or 3-aminopropyl triethoxysilane(APTES)for the first time via adsorption–precipitation–cross-linking.Compared with the freeα-amylase,the resultant magnetic cross-linkedα-amylase aggregates(PEI/PDA-M-CLEAs and N-M-CLEAs)exhibited excellent thermal and storage stability as well as pH stability.After storage at 25°C for 60 days,freeα-amylase only retained 60%of its initial activity,while PEI/PDA-M-CLEAs and N-M-CLEAs retained 80%and 78%of their initial activities,respectively.Furthermore,N-M-CLEAs and PEI/PDA-M-CLEAs showed good reusability.After 6 repeated uses,PEI/PDA-M-CLEAs and N-M-CLEAs still maintained 65%and 62%of their initial activities,respectively.Especially,PEI/PDA-M-CLEAs and N-M-CLEAs exhibited higher starch hydrolysis efficiency than freeα-amylase.The maximum dextrose equivalent(DE)values of starch hydrolysis by PEI/PDA-M-CLEAs and N-M-CLEAs reached 29.24%and 28.79%within 90 min,respectively.However,the maximum DE values of starch hydrolysis by the freeα-amylase was only 27.89%even in 150 min.The magnetic cross-linkedα-amylase aggregates could be introduced as effective biocatalyst for industrial applications in production of maltose syrups.

Synergistic precipitant powered self-assembly of papain for cross-linked enzyme crystals preparation

In this study,we prepared cross-linked enzyme crystals(CLECs)of papain to further broaden the application of the enzyme with high activity in extreme environments.Initially,papain crystals were successfully obtained based on the micro-batch,batch,and expanded batch crystallization experiments.Specifically,ammonium sulfate and polyethylene glycol 6000(PEG6000)were synergistically used as the precipitants,while L-cysteine was applied to enhance the activity of papain.Furthermore,the interaction between L-cysteine and papain was modeled by molecular docking technique.It was found that L-cysteine could form a hydrogen bond with aspartic acid residue(Asp)at site 158,and the electrostatic attraction with lysine residue(Lys)at site 156 was also quite obvious.Then the enzyme crystals were cross-linked by glutaraldehyde at optimized conditions.The papain CLECs were identified by various methods,and it was found that the thermal stability and enzymatic activity both increased compared to the raw enzyme.More importantly,it could be applied at more rigorous conditions,for example,pH of 4.

CRYSTALLIZATION AND MELTING OF POLY(ETHYLENE OXIDE)CONFINED IN NANOSTRUCTURED PARTICLES WITH CROSS-LINKED SHELLS OF POLYBUTADIENE

Small fixed aggregates of a poly(ethylene oxide)-block-polybutadiene diblock copolymer(PEO-b-PB)in THFsolution were obtained by adding a selective solvent for PB blocks,followed by cross-linking the PB shells.Themorphologies of the nanostructured particles with a cross-linked shell were investigated by atomic force microscopy andtransmission electron microscopy.The average behaviors of the PEO crystallization and melting confined within thenanostructured particles were studied by using differential scanning calorimetry experiments.For the deeply cross-linkedsample(SCL-1),the crystallization of the PEO blocks was fully confined.The individual nanoparticles only crystallized atvery low crystallization temperatures(T_cs),wherein the homogenous primary nucleation determined the overallcrystallization rate.For the lightly cross-linked sample(SCL-2),the confinement effect was T_c dependent.At T_c(?)42℃,thecrystallization and melting behaviors of SCL-2 were similar to those of the pure PEO-b-PB diblock copolymer.At T_c>42℃,SCL-2 could form PEO lamellae thicker than those of the pure PEO-b-PB crystallized at the same T_c.

RNA binding protein BOULE forms aggregates in mammalian testis

Amyloids have traditionally been considered pathologic protein aggregates which contribute to neurodegeneration.New evidence however increasingly suggests that non-pathological amyloids are formed in animals during normal development.Amyloid-like aggregate formation was originally thought to be a conserved feature of animal gametogenesis.This hypothesis was based on findings which suggest that regulated amyloid formations govern yeast meiosis by way of meiosis-specific RNA binding proteins.Additional support came from studies which demonstrate that DAZL,a mammalian gametogenesis-specific RNA binding protein,also forms SDS-resistant aggregates in vivo.Here,we report evidence of aggregated BOULE formations,another DAZ family protein,during sperm development.Data suggest that in mouse testis,BOULE forms SDS-resistant amyloid-like aggregates.BOULE aggregate formation correlates with dynamic developmental expression during spermatogenesis but disappeared in Boule knockout testis.We also mapped essential small region in vitro BOULE aggregations,immediately downstream DAZ repeats,and found that aggregations positively correlated with temperature.We also performed enhanced UV cross-linking immunoprecipitation on BOULE aggregates from mouse testes and found that aggregates bind with a large number of spermatogenesis-related mRNAs.These findings provide insight into the amyloidogenic properties of gametogenesis-specific RNA binding proteins as a conserved feature in mammalian reproduction.Further investigation is warranted to understand the functional significance of BOULE amyloid-like formation during mouse spermatogenesis.

生物炭对桑树/苜蓿改良沙化土壤团聚体稳定性及酶活性的影响

为探究生物炭对桑树/苜蓿改良沙化土壤团聚体粒径分布及稳定性的影响,通过室内盆栽实验,分别测定风沙土土壤团聚体粒径分布及稳定性、土壤有机质和养分质量分数及土壤酶活性,进而分析其对团聚体稳定性的影响。结果表明:施加生物炭能够显著提升土壤有机质和速效养分;桑树单独种植时土壤团聚体粒径分布优于桑树/苜蓿混种;桑树单独种植时生物炭添加量为2%可增加土壤团聚体稳定性;桑树/苜蓿混种时,生物炭添加量为0.5%可增加土壤团聚体稳定性;Pearson分析表明土壤磷酸酶的活性显著影响土壤养分变化;RDA分析进一步表明速效钾是导致土壤团聚体稳定性变异的主要环境因子。生物炭对桑树/苜蓿改良沙化土壤团聚体稳定性具有明显改善作用。

露天矿排土场接种AMF对3种植物根系发育与土壤团聚体稳定性的影响

[目的]探究丛枝菌根真菌(AMF)对植物根系和土壤团聚体稳定性的影响规律,为露天矿排土场生态修复提供理论基础。[方法]对复垦3年的紫穗槐、沙棘、柠条3种植物的对照和接菌样地的土壤理化性质、土壤酶活性、植物根系形态、土壤团聚体稳定性等指标进行采样和测定,并进行相关性分析。[结果]3种植物接菌处理能够显著提高植物根系的平均直径,接菌样地是对照的1.33~2.24倍;在压实土壤条件下,菌丝可能一定程度上代替植物细根系为植物提供水分和养分,使紫穗槐和沙棘样地接菌降低了根系的总根长。接菌显著提高了土壤酶活性,增加了土壤有机质含量,碱性磷酸酶活性最高提高了335.62%,脲酶活性最高提高了44.73%,易提取球囊霉素含量最高提高了82.56%,土壤有机质含量最高提高了64.74%。接菌通过增加土壤有机质含量,提高土壤酶活性等途径,显著增强了土壤团聚体的稳定性,平均重量直径提高了24.14%~34.29%,团聚体破坏率降低了18.25%~24.35%。[结论]露天矿排土场接种AMF能够显著提高土壤生物活性,提高养分含量,促进植物根系发育,从而提高土壤团聚体的稳定性。

长期秸秆还田对水稻土团聚体有机碳及胞外酶的影响

土壤团聚体有机碳和胞外酶对于改善土壤结构和提高土壤碳固存能力至关重要,且易受农艺生产措施的影响。为探讨秸秆还田下土壤有机碳组分及胞外酶活性变化,开展了35年水稻-小麦轮作试验。本试验设置了无肥区(CK)、化肥区(NPK)和秸秆还田+化肥区(NPKS),研究了不同农艺措施对土壤团聚体有机碳(SOC)及其活性组分(可溶性有机碳(DOC)、易氧化有机碳(EOC)、微生物生物量碳(MBC))含量与碳循环相关胞外酶(β-1,4-葡萄糖苷酶(BG)、β-1,4-木糖苷酶(BX)、β-D-纤维二糖水解酶(CBH))活性的影响。结果发现,大于0.25 mm团聚体中SOC、DOC和MBC含量显著高于小于0.25 mm粒级,且均以NPKS处理的效果最优,促进了土壤大团聚体有机碳组分更新。各粒级团聚体中MBC/SOC和DOC/SOC比值相对稳定,这表明MBC和DOC与SOC的动态变化趋势较为一致,可作为评价土壤有机碳的敏感指标。2~0.25mm粒级是团聚体胞外酶主要载体,均以NPKS处理活性最高;但大于2mm团聚体酶活性在不同农艺措施之间差异不显著。土壤团聚体中有机碳组分与胞外酶表现为互相促进的关系,其中SOC、DOC和MBC分配差异的主要影响因子为CBH,次要影响因子是BG;而EOC仅受到CBH的正向影响。CBH和BG可促进土壤有机碳周转,且在2~0.25 mm大团聚体中互促作用更剧烈。综上,长期秸秆还田配施化肥不仅有利于提升大团聚体碳的更新和周转速率,还提高了SOC含量,是稻田土壤可持续固碳的重要农艺途径。

2种马尾松混交林土壤微生物特性及其与团聚体稳定性耦合关系

【目的】探究2种马尾松人工混交林间土壤微生物群落结构差异,以及2种林分土壤团聚体稳定性与其微生物群落结构、土壤酶活性的耦合关系。【方法】以三峡库区马尾松杉木混交林和马尾松杉木栎类混交林为研究对象,通过比较分析0~10 cm土层的不同粒径土壤团聚体微生物群落结构及微生物生长代谢现状,探究影响团聚体稳定性和微生物群落结构的主要影响因素。【结果】(1)2种马尾松混交林之间的土壤团聚体稳定性、微生物总生物量及其群落多样性均无明显差异;(2)从酶化学计量特征来看,2种马尾松混交林土壤微生物生长代谢受到磷(P)限制;(3)土壤丛枝菌根真菌、放线菌和革兰氏阳性菌、革兰氏阴性菌的生物量在不同粒径土壤团聚体之间无明显差异;(4)土壤全钾含量对微生物群落结构影响程度最大。大团聚体中N-乙酰-β-D-葡萄糖苷酶(NAG)活性是驱动土壤团聚体稳定性的关键因素。【结论】为提高三峡库区马尾松林地土壤质量,应多关注NAG活性对环境变化的响应。为缓解P限制对植被生长发育的影响,可在马尾松人工林中营造P分配能力更强和P利用效率更高的树种。

两种芒萁覆盖度下毛竹林土壤酶活性及生态化学计量特征比较研究

[目的]探究毛竹林下不同盖度芒萁对土壤酶活性及生态化学计量特征的影响。[方法]在亚热带选取低芒萁盖度(PE:7.75%)和高芒萁盖度(DD:63.25%)的毛竹林为研究对象,测定土壤团聚体不同粒径碳(C)、氮(N)、磷(P)含量、参与土壤C、N、P循环的酶活性及其生态化学计量特征(E_(C:N:P))和不同类群微生物量。[结果](1)PE和DD样方土壤β-葡糖苷酶活性和N-乙酰-葡糖苷酶活性无显著差异,与PE样方相比,DD样方显著增加了亮氨酸氨基肽酶、酸性磷酸酶和多酚氧化酶活性,但显著降低了过氧化物酶活性,且这种差异主要在大团聚体和中团聚体。(2)与PE样方团聚体粒径间E_(C:N)和E_(N:P)无差异不同,DD样方微团聚体E_(C:N)显著高于大和中团聚体,而E_(N:P)显著低于大和中团聚体;大和中团聚体E_(C:N:P)在PE和DD样方之间无显著变差异,但DD样方微团聚体的E_(N:P)和E_(C:P)显著低于PE样方。(3)除丛枝菌根真菌和放线菌分别调控PE和DD样方土壤酶活性变异外,土壤全磷含量(TP)也是影响DD样方酶活性变异的主要因子;此外,土壤全氮含量(TN)和TP分别是调控大团聚体和中团聚体土壤酶活性变异的重要因子,且大团聚体土壤酶活性变异亦受到真菌生物量影响。[结论]毛竹林下不同盖度芒萁群落显著改变了土壤团聚体不同粒径参与C、N、P循环的酶活性及其生态化学计量特征,研究区生态系统同时受到C和P的限制作用,但P限制作用更强,且高盖度的芒萁种群加剧了该作用。

复合蛋白酶交联酶聚集体制备枸杞蛋白多肽

该研究利用交联酶聚体技术制备出复合蛋白酶交联酶聚体固定化酶,以酶活回收率为指标,通过单因素实验得到复合蛋白酶交联酶聚集体最佳制备条件:风味蛋白酶与木瓜蛋白酶比例为3∶1,沉淀剂硫酸铵浓度为60%,戊二醛浓度0.5%,交联时间为50分钟,交联pH为7.5。此时最大酶活回收率为80.32%。相比单一蛋白酶,复合蛋白酶交联酶聚集体具有更好的热稳定性和pH稳定性,同时表现出良好的连续多次水解枸杞蛋白的性能。以蛋白水解度为指标,优化后复合蛋白酶交联酶聚集体最佳水解条件为:温度为60℃,pH为6,酶浓度为10 mg/mL,水解时间为100 min,在此条件下枸杞蛋白水解度为41.21%,比游离复合蛋白酶提高了6.9%。

Urban Soil Compaction Remediation by Shallow Tillage and Compost in Hydroseeded Lawn

Construction activities often involve removal of topsoil and compaction of the exposed soil by heavy equipments. Such compacted soils with low organic matter can lead to low infiltration and poor vegetation establishment. The objective of this study was to investigate the efficacy of tillage (shallow till) and compost on soil physical and biological properties in a hydroseeded lawn as a post-construction best management practice for soil compaction remediation. The experimental site received a total of four land treatments in five replicated trials and it was hydroseeded with common Bermuda grass: 1) No Tillage + Compost (NT-C), 2) No Tillage + No Compost (NT-NC;control), 3) Tillage + Compost (T-C), and 4) Tillage + No Compost (T-NC). Bulk density (BD), infiltration rate (IR), and wet aggregate stability (WAS) in each plot were measured to assess soil physical properties while soil organic matter (SOM) and enzyme activity (β-glucosidase, acid-phosphatase, and alkaline-phosphatase) were measured for soil biological properties. Over a 15-months of monitoring period, the shallow tillage loosened the soil initially, but its effect on BD without compost was diminished to control plot level (NT-NC) within 4 months after hydroseeding. Both tillage and compost led to an increase in IR, and it remained higher than control by 2 - 3 times throughout the observation period. The WAS and β-glucosidase activity decreased in tilled plot unless there was compost application. Turfgrass showed greener leaves and aggregated roots in the compost-amended plots (NT-C and T-C). Our results suggest that compost application plays a key role in improving soil physical and biological properties in hydroseeded lawns from construction sites.

有机肥等氮量替代化肥对稻麦轮作水稻土有机碳矿化特征的影响

采用大田试验和室内培养试验相结合的方法,研究有机肥等氮量替代化学氮肥对稻麦轮作模式下土壤有机碳赋存转化及功能酶活性的影响。结果表明:连续3年有机肥等氮量替代化学氮肥后土壤有机碳含量提高2.0%~17.5%,全氮含量提高1.4%~30.5%。替代10%最有利于提升>2.00和<0.053 mm团聚体中有机碳和全氮含量,替代40%最有利于提升0.25~2.00和0.053~0.25 mm团聚体中有机碳和全氮含量。有机肥等氮量替代化学氮肥各处理土壤有机碳矿化速率整体上高于仅施化学氮肥处理,其中替代30%、40%最有利于提升土壤有机碳累积矿化量,前者也最有利于提升土壤有机碳矿化率。有机肥等氮量替代化学氮肥处理会导致土壤外切-β-1,4-葡聚糖酶/纤维二糖苷酶(S-C1酶)活性下降,替代20%最有利于提升土壤蔗糖酶和β-葡萄糖苷酶活性,替代50%最有利于提升土壤酸性磷酸酶活性。综上,有机肥等氮量替代化学氮肥可显著提高土壤0.025~2.00和>2.00 mm团聚体碳氮含量,土壤有机碳含量与土壤全氮含量以及β-葡萄糖苷酶与土壤蔗糖酶呈显著正相关,替代20%有利于土壤有机碳矿化,替代40%有利于土壤碳固定。

Enzyme Activities and Microbial Communities in Subtropical Forest Soil Aggregates to Ammonium and Nitrate-Nitrogen Additions

A laboratory incubation experiment was established to examine the impacts of nitrate and ammonium nitrogen additions on soil microbial attributes of a subtropical Pinus elliottii forest ecosystem in southern China. Soils were subjected to three different treatments： the control with no nitrogen addition （CK）, the ammonium nitrogen addition （NH4^＋-N）, and the nitrate nitrogen addition （NO23^-N）. Samples from bulk and two different size fractions （macroaggregate （〉250 pm） and microaggregate （53-250 μm）） were analyzed for soil properties, enzyme activities and microbial communities on day 7 and 15 of the incubation. Our study demonstrated that NH4^＋-N had a 9rearer influence on soil microbial activities than NO3-N. NH4^＋-N additions resulted in significant increases in 13-1,4-glucosidase （βG） and β-1,4-N-acetyl glucosaminidase （NAG） enzyme activities in bulk, macroaggregate and microag- gregate soils after 7 and 15 days incubation. NO3^-N additions only significantly increased in βG and NAG enzyme activities in bulk, macroaggregate soils after 7 and 15 days incubation, but not in microaggregate. All NH4^＋-N and NO3-N additions resulted in significant increases in gram-positive bacterial PLFAs in microaggregates. Only a significant correlation between soil nutrient contents and enzyme activities in macroaggregates was founded, which suggests that the soil aggregation structure played an important role in the determining enzyme activities.

有机无机氮肥比例对稻田土壤肥力和作物产量的短期效应

【目的】研究短期内(<5年)有机无机氮配施比例对土壤肥力以及水稻产量的影响,以明确提升地力与兼顾产量的养分管理措施。【方法】田间定位试验于2017—2021年在长江中下游的红壤双季稻田进行。共设6个处理:不施肥(CK),单施化肥(CF),有机氮比例分别为25%、50%、75%与100%的有机无机肥配施处理(25%ON,50%ON,75%ON,100%ON)。2021年,早、晚稻成熟后测产;晚稻收获后采集耕层土壤样品,分析土壤物理性状(容重与大团聚体含量)、化学性状(pH、有机质、全氮、全磷、全钾、有效氮、有效磷、速效钾、有效锌、有效硅)与生物学性状(脲酶、酸性磷酸酶、β-葡糖苷酶、微生物生物量碳、微生物生物量氮),采用土壤肥力综合指数(IFI)评价不同比例有机肥料的培肥效果,运用偏最小二乘路径模型(PLS-PM)分析有机无机肥配合比例对IFI以及产量的影响。【结果】随着有机肥比例的提高,有机无机肥配施提升土壤物理、化学、生物学性状的效果也随之提升。土壤有机质含量和β-葡糖苷酶活性与其它所有指标的相关关系均达显著水平,有机碳含量与碳循环过程对土壤物理结构、养分以及微生物活性均有较强影响。相对于其他指标,土壤全磷与有效磷的变异系数较大,受有机肥投入的影响较大。施肥显著提高了土壤IFI,有机无机肥配施的肥力指数显著高于单施化肥,且随着有机肥配施比例升高而递增,而双季稻产量则随着有机肥配施比例升高而递减,有机肥配施比例≤50%时,产量与单施化肥持平,>50%时表现为减产。PLS-PM分析结果显示,有机肥和无机肥投入对IFI均有显著影响,有机肥的效应大于无机肥;有机肥对产量无显著影响,而无机肥投入量对产量影响显著。【结论】有机无机肥配施可以全面改善土壤环境,提高土壤肥力,且有机肥配施比例越高效果越好。但如果培肥时间较短(5年以内),化肥氮对产量的贡献占绝对优势,有机氮的投入比例应控制在50%以下,才能兼顾地力提升与产量的维持。

氮添加对马尾松人工林土壤团聚体氮矿化及土壤酶活性的影响

土壤氮库是生态系统氮素重要的源和汇。以三峡库区马尾松(Pinus massoniana)人工林为研究对象,从团聚体视角出发分析土壤养分和酶活性对氮添加的响应规律,以及相应的变化对氮矿化的影响,为预测该地区在大气氮沉降持续增加的背景下土壤氮动态提供参考。设置4种量的氮添加处理(N0:0 kg N hm^(-2)a^(-1);N30:30 kg N hm^(-2)a^(-1);N60:60 kg N hm^(-2)a^(-1);N_(90):_(90) kg N hm^(-2)a^(-1)),将土壤按粒径分为>2000μm(大团聚体)、250—2000μm(小团聚体)和<250μm(微团聚体)3个组分的团聚体,观察团聚体氮矿化特征。结果表明:(1)与对照相比,N30和N60处理提高了有机质(SOM)含量,但土壤SOM和全氮(TN)含量在N_(90)下开始出现下降;氮添加降低了土壤速效磷(aP)含量,在小团聚体中表现最为显著。除微团聚体中的POD和NAG以外,其余3种酶的活性均在N30和N60处理之下被提高。(2)土壤平均净硝化速率整体高于土壤平均净氨化速率;大团聚体和小团聚体中净氨化速率在氮添加处理后显著降低,大团聚体净硝化速率低于其他两个粒径;土壤净氮转化速率在N_(90)处理下最高。(3)土壤养分和无机氮含量与土壤酸性磷酸酶(AP)、N-乙酰-β-D-葡糖苷酶(NAG)、过氧化物酶(POD)、硝酸还原酶(NR)和脲酶(UE)的活性呈显著相关,酶活性变化是多因子综合作用的结果;RDA分析显示,UE与土壤净氨化速率存在显著正相关,NAG和POD是与净氮转化速率分别存在显著正相关和显著负相关的关键土壤酶。综上所述,硝化作用是土壤净氮转化的主要贡献者,微团聚体在土壤氮矿化中发挥主要作用,NAG和POD是改变土壤净氮转化的主要生物酶。此外,氮添加会引起土壤氮素的流失,引起土壤的磷限制,并对土壤养分循环产生显著影响。

秸秆还田对银北盐碱地土壤主要肥力指标及细菌群落多样性的影响

为探索粉碎玉米秸秆对银北盐碱地土壤肥力的可持续提升效果,于2016-2021年建立5a连续玉米秸秆粉碎还田定位试验,以未还田为对照,分别设置1/3全量还田(3000 kg·hm^(-2))、2/3全量还田(6000kg·hm^(-2))、全量还田(9000 kg·hm^(-2))处理,分析不同还田量下土壤肥力及细菌群落多样性变化。结果表明:相比未还田处理,秸秆还田处理虽降低0~20 cm土层含水量,但能显著增加土壤水稳性团聚体的平均质量直径,且降低土壤团聚体破坏率。其中,还田量9000 kg·hm^(-2)处理相比未还田处理显著降低土壤全盐含量15.06%,增加有机质14.06%,增加全氮50.82%及微生物量氮71.75%。酶活性在秸秆还田措施下均明显提升,但各处理下差异不显著。基于16s rDNA测序发现,相比未还田处理,秸秆还田增加不同分类水平下的OTU数,还田量9000 kg·hm^(-2)处理显著增加Chao1、Simpson指数以及优势菌群变形菌门的相对丰度。相关性发现,土壤微生物量氮、土壤含水量与群落结构组成间存在显著性差异。总之,秸秆还田有利于改善盐碱地土壤结构,增加土壤养分及微生物氮含量,抑制盐分表聚,提升土壤酶活性,提高土壤细菌微生物多样性及丰富度。

不同种植模式对坡耕地红壤团聚体中酶活性及养分含量的影响

为探究不同种植模式下坡耕地红壤团聚体中的酶活性和养分含量,为改善耕地质量提供理论依据,以坡耕地红壤为研究对象,设置大豆单作(DD)、玉米单作(MM)、大豆玉米间作(MD)、裸地(CK)4个处理,利用干筛法获得2~1、1~0.25、<0.25 mm粒径团聚体,并测定了其中的酶活性和养分含量。结果表明:①与CK、DD、MM处理相比,MD处理显著提高了2~1 mm粒径团聚体的含量,增幅分别为22.2%、13.3%、16.2%。②MD处理显著提高了2~1 mm粒径团聚体中的有机质、有效磷、碱解氮含量,分别较DD和CK处理提高11.9%、29.2%,51.1%、57.5%和16.5%、29.1%;速效钾含量均表现为DD处理显著高于CK、MM、MD处理。③与CK、DD、MM处理相比,MD处理显著提高了2~1 mm和1~0.25 mm粒径团聚体中的脲酶活性,增幅分别为61.0%、18.8%、14.5%和65.0%、17.9%、13.8%,显著提高2~1 mm粒径团聚体中的蔗糖酶活性和<0.25 mm粒径团聚体中的酸性磷酸酶活性,增幅分别为63.8%、57.1%、32.8%和80.4%、44.3%、74.1%。④冗余分析表明,2~1 mm粒径团聚体中的脲酶和蔗糖酶活性与有效磷、有机质含量显著正相关,1~0.25 mm粒径团聚体中的酶活性与有机质、有效磷、碱解氮含量显著正相关,<0.25 mm粒径团聚体中的酶活性与碱解氮、有效磷含量显著正相关。研究表明,合理的种植模式不仅可以促进大团聚体的形成,还能提高大团聚体中的酶活性和养分含量,从而提高土壤肥力,改善耕地质量。

复合生物炭基功能肥对植烟根际土壤水稳性团聚体和酶活性的影响

【目的】探明复合生物炭基功能肥对植烟根际土壤水稳性团聚体和酶活性的影响,为优质烤烟专用生物炭基肥的研制提供参考。【方法】采用田间小区试验,以单施生物炭基肥为对照(CK),研究生物炭基肥60 g/穴+氟吡菌酰胺1 g/穴(T1)和生物炭基肥60 g/穴+淡紫紫孢霉2×10^(9)个孢子/穴(T2)对植烟根际土壤团聚体稳定性和关键酶活性的影响。【结果】连续施肥2年后,大方和金沙试验地各处理[0.25,+∞)mm粒级土壤水稳性团聚体的含量均增加。与2020年比,2021年大方和金沙单施生物炭基肥、生物炭基肥+氟吡菌酰胺和生物炭基肥+淡紫紫孢霉处理[0.25,+∞)mm粒级土壤水稳性团聚体含量分别增加74.2%、39.2%、3.1%和99.5%、117.0%、135.5%;土壤水稳性团聚体平均质量直径(MWD)分别增加240.0%、161.7%、47.0%和270.3%、397.7%、310.7%,几何平均直径(GMD)分别增加378.5%、224.4%、68.2%和391.2%、462.8%、331.2%,且MWD和GMD均与[5,+∞)mm粒级土壤水稳性团聚体呈极显著正相关关系。与CK比,2020年大方试验地生物炭基肥+氟吡菌酰胺处理土壤脲酶、蔗糖酶和过氧化氢酶活性分别显著提高21.6%、37.2%和12.9%,生物炭基肥+淡紫紫孢霉处理土壤脲酶和蔗糖酶活性分别显著提高22.1%和35.9%;金沙试验地生物炭基肥+氟吡菌酰胺处理土壤过氧化氢酶活性显著提高13.2%,生物炭基肥+淡紫紫孢霉处理土壤蔗糖酶和过氧化氢酶活性分别显著提高105.2%和11.2%。2021年大方试验地生物炭基肥+氟吡菌酰胺处理土壤脲酶和蔗糖酶活性分别显著降低11.2%和61.8%,生物炭基肥+淡紫紫孢霉处理土壤脲酶、蔗糖酶和过氧化氢酶活性分别显著降低20.9%、59.2%和4.0%;金沙试验地生物炭基肥+氟吡菌酰胺处理土壤脲酶、蔗糖酶和过氧化氢酶分别显著降低10.3%、37.7%和9.1%,生物炭基肥+淡紫紫孢霉处理分别显著降低15.7%、29.0%和11.2%。【结论】连续2年施用复合生物炭基功能肥对大方土壤水稳性团聚体的作用效果表现不明显,金沙以施用生物炭基肥60 g/穴+淡紫紫孢霉2×10^(9)个孢子/穴效果最佳;土壤脲酶、蔗糖酶和过氧化氢酶活性表现出2020年提高,2021年降低现象。

一种基于儿茶素的多酚氧化酶交联聚集体制备及其高效催化合成茶黄素-3,3’-双没食子酸酯研究

为了更加高效低成本地制备茶黄素,以儿茶素作为多酚氧化酶蛋白的交联试剂,对巨大芽孢杆菌(Bacillus megaterium)来源的多酚氧化酶进行了酶交联聚集体的制备并应用于茶黄素-3,3’-双没食子酸酯的合成。通过对酶交联参数优化以及交联前后的酶催化性能研究,结果表明,在pH 4.0,EGCG为0.5 mg·mL^(-1),多酚氧化酶活性200 U·mL^(-1),交联时间50 min时,可以获得交联酶的最佳酶活回收率。与游离酶相比,交联酶表现出更优异的催化性能(热稳定性、有机溶剂耐受性、底物耐受性)。交联酶被用于合成茶黄素-3,3’-双没食子酸酯时,产物质量浓度可达800μg·mL^(-1),且交联酶能被重复循环使用至少3个批次,利用该方法制备茶黄素,可以显著降低酶的应用成本,具有潜在工业化应用价值。

陶粒与微生物菌剂对露天煤矿土壤的改良及植物生长效果

采用盆栽种植紫花苜蓿,设置空白对照(原土种植紫花苜蓿)、陶粒1%、陶粒3%、陶粒5%、微生物菌剂0.1%、微生物菌剂0.3%、微生物菌剂0.5%不同处理,分析以陶粒、微生物菌剂作为土壤改良剂时,其对土壤团粒结构、理化性质、酶活性和植物生长状况的影响。结果表明:表面疏松多孔的陶粒增加了土壤的蓄水保持能力,陶粒添加量为1%时土壤改良效果最好,随着陶粒添加量增加土壤砂粒含量、团聚体含量、含水率、有机质含量、过氧化氢酶活性、蔗糖酶活性、碱性磷酸酶活性、脱氢酶活性呈逐渐减小趋势,过量陶粒没有改良效果,甚至破坏原始土壤。微生物菌剂直接提高土壤中有益菌含量,适量的微生物菌剂通过对植物根系分泌物、土壤有机质、矿质颗粒的分解,提高了土壤有效养分,微生物菌剂添加量为0.3%时改良效果最佳,过量则起到抑制作用。