咸蛋黄快速腌制过程中理化性质变化规律

该研究以新鲜蛋黄为原料,利用快速腌制模具,探究在咸蛋黄的上表面添加食盐单侧腌制过程中,食盐添加量和腌制时间对咸鸡蛋黄快速腌制过程中形貌特征和理化性质变化规律的影响。借助多种仪器分析手段对蛋黄腌制过程中形貌与物性的变化、水分及盐分的迁移规律进行了表征。低场核磁及成像结果表明：在腌制过程中,蛋黄中的水分不断向外迁移,含水率显著降低,当增加食盐的添加量和延长腌制时间,会加快水分的迁移速率;原子吸收结果表明：增加食盐添加盐量越多和腌制时间越长盐分迁移速率越快,质构、色差结果共同表明咸蛋黄腌制过程中,由于水分的向外迁移和盐分的向内渗入,使得蛋黄的蛋白质发生聚集使颜色加深;同时与市售整个腌制后分离的鸡蛋黄产品相比,当腌制时间为7d,添加盐量为3%;腌制时间为3d,添加盐量为5%时,所得的样品与市面的成品咸鸡蛋黄的感官品质及量化指标差异不显著（P<0.05）,为咸蛋黄单侧腌制技术提供理论的可行性。     

超声波-脉动压联用快速腌制咸鸭蛋的工艺参数优化

咸鸭蛋的腌制周期很长,一般夏季20～30 d、春秋季40～50 d。为了提高咸蛋的腌制效率,采用超声波-脉动压联用技术,选取高压幅值、高压脉动比和超声波作用时间为影响因素,通过单因素和正交试验,测定咸蛋腌制过程中蛋清含盐量和蛋黄含盐量的变化,对超声波-脉动压联用技术在咸蛋快速腌制中的工艺参数进行优化。结果表明：采用质量分数为24%食盐溶液,在恒温30℃条件下腌制3 d,综合咸蛋品质和食盐传质速率得出最佳工艺参数：高压幅值为140 kPa,高压脉动比为4 min：16 min,超声波作用时机应在第1天,超声波脉动比为2 min：10 min,超声波作用时长为132 min,可以腌制出效果较好的咸蛋,蛋白食盐含量为4.61%,蛋黄食盐含量为2.12%,而含盐量差值只有2.49%。感官评定此组咸蛋具有蛋白细嫩、咸味适中;蛋黄松沙、含油、咸味可口的特点。同时生产周期比传统腌制方法缩短了90%,可为咸蛋的工业化生产提供技术参考。     

咸蛋盐水腌制动力学研究

以鲜鸡蛋为原料，采用盐水腌制法，研究腌制温度、时间和盐水浓度对咸蛋成熟度的影响。试验结果表明：随着腌制温度、时间的延长和盐水浓度的增加，含盐量及蛋黄指数迅速升高，蛋清的含盐量明显高于蛋黄，且含盐量由内到外呈梯度分布，蛋黄外层含盐量明显高于中心点。建立的腌制条件对蛋品含盐量及蛋黄指数的拟合方程，能较好地描述腌制温度、时间和盐水浓度对咸蛋成熟的影响。     

传统风干牦牛肉加工中肌原纤维蛋白氧化与体外消化性变化

为了评价传统风干牦牛肉在加工过程中肌原纤维蛋白消化率的变化,并探讨蛋白质氧化影响其消化性的潜在机制。在牦牛肉自然风干加工过程中(40 d)采集样本,测定肌原纤维蛋白羰基、巯基、二硫键、二聚酪氨酸、粒径分布、体外消化率及脂质氧化等指标,并分析脂质氧化和蛋白质氧化对蛋白质消化性的影响。结果显示,脂质初级氧化产物(Primary Oxidation Value, POV)、硫代巴比妥酸反应物(Thiobarbituric Acid Reaction Substrates, TBARS)和蛋白质羰基化合物随加工时间的延长而显著增加(P0.05),并且相互间存在极显著相关性(P0.01)。此外,二硫键和二聚酪氨酸含量显著增加(P0.05),这是蛋白质交联的主要形式。蛋白质被胃蛋白酶和胰蛋白酶总的水解率在整个加工过程中降低了19.58%(P0.05),蛋白质的水解率与羰基、二硫键、二聚酪氨酸和蛋白质粒径呈现极显著负相关性(P0.01)。综上所述,在风干牛肉加工期间,脂质氧化产物促进了蛋白质氧化,蛋白质的羰基化和交联导致蛋白酶对蛋白质的水解率降低。研究结果对了解风干牦牛肉传统加工方式和进一步改进加工工艺具有积极的促进作用。     

超高压处理对低盐牛肉乳化肠品质的影响

为探究超高压(UHP)处理对低盐牛肉乳化肠品质的影响,本试验以低盐牛肉乳化香肠(食盐添加量1.4%)为研究对象,以未经UHP处理的C1组(食盐添加量2.8%)和C2组(食盐添加量1.4%)为对照,比较了不同压力(100、200、300、400 MPa)对低盐牛肉乳化肠感官品质、理化指标和微生物指标的影响。结果表明,UHP处理降低了处理组乳化肠的菌落总数(TVC)和挥发性盐基氮(TVB-N)值,当压力≥200 MPa时,乳化肠的TVC和TVB-N值均显著低于C1和C2组(P<0.05);随着压力的增大,蒸煮损失先减小后增大,100和200 MPa处理组乳化肠蒸煮损失最低,分别为3.00%和3.97%,且均显著低于C2组(P<0.05);与C2组相比,UHP处理使低盐乳化肠的硬度、弹性、咀嚼性、内聚性都有所增加,并提高了产品的咸味分数,对多汁性、总体风味及总体可接受性具有改善作用;UHP处理促进了脂质氧化,当压力为300 MPa时,硫代巴比妥酸反应产物(TBARS)值最高;亚硝酸盐含量不受UHP处理的影响,且符合肉制品亚硝酸盐残留量要求。综上,UHP处理能够改善低盐牛肉乳化香肠的品质特性,这为低盐肉制品的开发提供了技术支持和理论依据。     

腌制剂对脉动压腌制咸鸡蛋的影响

为丰富咸蛋品种,改善咸蛋风味,提高咸蛋的腌制速率,应用脉动压技术,以鸡蛋为原料,选取白酒、香辛料、柠檬酸为影响因素,通过单因素及正交试验,考察咸蛋腌制中蛋质量增加率、蛋清含盐率和蛋黄含盐率的变化,对腌制禽蛋工艺进行优化。结果表明：白酒和柠檬酸对盐分渗入有促进作用,而香辛料则阻碍了盐分的渗入,影响咸蛋综合评分的因素从高到低依次为香辛料、白酒、柠檬酸,且香辛料对咸蛋综合评分的影响显著,柠檬酸对蛋清含盐率的影响显著。在高压幅值140 kPa、脉动比2.5 min/5min饱和食盐溶液中腌制96 h,风味咸蛋腌制     

食盐添加量对预制鲈鱼冷藏保鲜及热加工特性的影响

为研究不同食盐添加量(0~2.0%)对鲈鱼冷藏保鲜及热加工特性的影响,采用差示扫描量热法,研究鲈鱼鱼肉的含水率、冰点、变性温度、热焓和比热容等热特性并进行分析。研究发现,预制鲈鱼的冰点和含水率随食盐添加量的增加而逐渐降低;加热温度50℃附近吸热峰的起始温度、终止温度及变性热焓随食盐添加量的增加均逐渐降低;70℃附近吸热峰仅明显存在于新鲜鲈鱼样品中,其他食盐添加量条件下70℃附近吸热峰消失;鲈鱼鱼肉的比热容随食盐添加量的增加未呈现明显的变化趋势(P0.05),当鱼肉处于冻结状态、肌球蛋白及肌动蛋白处于变性状态时,2.0%食盐添加量鲈鱼的比热容最高,当鱼肉处于未冻结状态时,1.0%食盐添加量鲈鱼的比热容最高。研究表明:在不同食盐添加量(0~2.0%)条件下,随着食盐添加量的增多,鲈鱼冰点和含水率逐渐下降,肌球蛋白变性温度向低温方向移动,峰高逐渐降低,变性热焓逐渐下降,肌动蛋白峰消失;添加食盐的鲈鱼比热容变化皆小于新鲜鲈鱼(除1.0%食盐添加量)(P0.05);在不同食盐添加量(0~2.0%)条件下,未冻结鱼肉的比热容高于冻结鱼肉(P0.05),加工后的鱼肉的比热容高于未加工的鱼肉(P0.05)。研究结果为预制鲈鱼热加工和低温贮藏的品质控制提供参考。     

不同贮藏条件下荷花粉脂质氧化与色泽降解动力学模型

为了减少干燥后荷花粉贮藏过程中品质的劣变,该研究选用可真空和避光的包装材料,分别研究了30 d贮藏过程中温度(4、20、30℃)、光照(避光、非避光)和氧气(真空、常压)对荷花粉黄色度值(b*值)、过氧化氢值(peroxide value,POV)和硫代苯巴比妥酸反应底物值(thiobarbituric acid reactive substances,TBArs)变化动力学的影响;同时,采用零阶和一阶数学模型对试验数据进行模拟。结果表明:贮藏温度对荷花粉贮藏过程中品质劣变具有显著影响。在避光真空包装条件下,温度为20和30℃贮藏30 d,与4℃贮藏条件相比,荷花粉黄色度值显著降低(P0.05),POV值和TBArs值显著上升(P0.05);贮藏温度为4℃,真空包装贮藏发现,光照对荷花粉POV值的影响不显著(P0.05),但明显加快了脂质氧化的传播速度,非避光条件下贮藏30 d,TBArs值上升了7.42 mg/kg;零阶模型可较好的预测荷花粉贮藏过程中脂质TBArs值的变化,一阶模型可较好的预测荷花粉贮藏过程中黄色度和脂质POV值的变化规律。研究结果为脱水后荷花粉贮藏过程中品质劣变规律的探索及贮藏条件的选择提供了一定的基础。     

微咸水滴灌条件下沙穴种植的土壤水盐二维空间分布规律

河套灌区重度盐碱土具有结构性差、导水率低的特点,且该地区淡水资源短缺,为提高土壤水入渗性能,合理开发利用微咸水资源,可在滴头下方设置沙穴并利用微咸水灌溉。为探明不同矿化度微咸水滴灌的沙穴种植条件下二维土壤水盐分布规律,采用室内50 cm×50 cm二维土槽模拟试验,设置蒸馏水(0 g/L),2.0,3.0,4.0 g/L 4种不同矿化度处理,试验历时100 h。结果表明:在深度5 cm距滴头两侧15~20 cm及滴头下方25 cm的盐碱土处,土壤含水量较高,沙土土壤含水率随着矿化度的增加而增加,盐碱土土壤含水率随着矿化度的增加呈现先增加后降低的趋势,采用3.0 g/L灌溉水滴灌时,盐碱土含水率最大(变异系数为7.64%),说明利用3.0 g/L微咸水灌溉可有效提高沙穴种植条件下土壤含水率;入渗100 h后盐分主要聚集在滴头下方25~30 cm处,沙穴结构试验中,灌溉水矿化度为4.0 g/L的情况下土壤平均电导率最大(变异系数为50.59%),水平方向盐分淋洗效果优于垂直方向,且灌溉水矿化度越低,淋洗效果越显著,蒸馏水处理脱盐率为13.99%,灌溉水矿化度为2.0,3.0,4.0 g/L时积盐率分别为7.93%,14.57%,30.05%,脱盐半径随矿化度的增大而减小,3.0 g/L与2.0 g/L积盐量差异不显著(P=0.460>0.05),与4.0 g/L处理下积盐量差异显著(P=0.024<0.05)。结合土壤水盐空间分布规律,利用3.0 g/L微咸水可提高盐碱土土壤含水率,控制沙穴种植结构土壤积盐量,提高根系层土壤保水性。     

放养条件下密度和补饲量对蛋鸡生产性能及蛋黄胆固醇含量的影响

选择45周龄体重接近的健康本地鸡441只,随机分为7组,在山西省太谷县生态养鸡场进行2(补饲量)×3(密度)两因子放养试验,研究林下种植苜蓿不同放养密度与补饲量对蛋鸡生产性能和蛋黄胆固醇含量的影响。补饲量设自由采食量50%、70%两个处理,密度为每667m2 100只、250只、400只3个处理,以笼养全程自由采食为对照,每组3个重复,每重复3个小区用于轮牧,小区面积为62 m2;预试期7 d,正试期70 d。结果表明:补饲量和放养密度互作对平均产蛋率影响极显著(P0.01),对蛋重和料蛋比影响不显著(P0.05)。笼养+自由采食组(CK)与补饲量70%、100只·667m-2组蛋重、平均产蛋率及料蛋比差异不显著(P0.05),但产蛋率显著高于其他各组(P0.05),蛋重显著高于补饲量50%、100只·667m-2组(P0.05),料蛋比显著低于补饲量50%组(P0.05)。补饲量和放养密度互作对蛋黄重、蛋黄胆固醇含量和全蛋胆固醇含量影响不显著(P0.05);放养密度对全蛋胆固醇含量影响极显著(P0.01)。笼养+自由采食组蛋黄重极显著高于补饲量50%、100只·667m-2组(P0.01),蛋黄胆固醇含量和全蛋胆固醇含量显著高于100只·667m-2组(P0.05)。补饲量70%下,100只·667m-2放养密度对牧草的破坏性小于其他放养密度。结合产蛋性能、蛋黄胆固醇含量以及草地保护,以70%补饲量+100只·667m-2组养殖模式较好,效果较佳。     

A comparison of two modified Kjeldahl digestion techniques for multi‐element plant analysis with conventional wet and dry ashing methods

Abstract

The efficiency of two modified Kjeldahl procedures (H₂SO₄‐H₂‐O₂‐Li₂SO₄‐Se and H₂SO₄‐Na₂SO₄) for digestion of plant tissue for analysis of P, K, Ca and Mg contents was compared with a conventional wet (HNO₃‐HClO₄) and a dry ashing procedure. Six plant tissues were chosen as test material: leaves of Malus pumila Mill., Medicago sativa L., Dactylis glomerata L., fruit and wood tissue of M. pumila and Nothofagus mensiesii Oerst. leaf litter. Apart from low P contents of M. pumila wood tissue by dry ashing, the mean P, K, Ca and Mg contents as determined after the four digestion procedures were in good agreement. Furthermore, the precision of the data for each element was generally quite similar for each of the digestion methods. The N contents determined by the two modified and a conventional Kjeldahl procedure (H₂SO₄‐K₂SO₄‐CuSO₄‐Se) also agreed closely.     

草坪缓冲带限制斜坡上葡萄园敌草隆向地表水和地下水迁移效果的研究

Trichloroethylene (TCE), as one of the most common chlorinated organic compounds in soils and aquifers at many industrial sites, is carcinogenic and often recalcitrant in environment. TCE degradation in artificially contaminated soil samples was conducted using Fenton-like processes, i.e., by addition of excess hydrogen peroxide (H2O2 ). H 2 O 2 could directly oxidize TCE without addition of ferrous iron in contaminated soil. Under the optimal condition (H2O2 concentration of 300 mg kg 1 , pH at 5.0, and reaction time of 30 min), the removal efficiency of TCE in the soil was up to 92.3%. When the initial TCE concentration increased from 30 to 480 mg kg 1 in soil, the TCE removal rates varied from 89.2% to 86.6%; while the residual TCE in soil ranged from 2.28 to 47.57 mg kg 1 . Results from successive oxidations showed that the TCE removal rate with the TCE concentration of 180 mg kg 1 increased slightly from 91.6% to 96.2% as the number of successive oxidation cycle increased from one to four. Therefore, increasing the frequency of H2O2 oxidation was perhaps a feasible way to increase TCE removal rate for TCE-contaminated soil.     

冷藏和冻藏对牦牛瘤胃平滑肌氧化稳定性及加工品质的影响

为探明4℃冷藏和-18℃冻藏对牦牛瘤胃平滑肌脂肪和蛋白质氧化及其加工特性的影响,以PE薄膜和PE真空包装的牦牛瘤胃为研究对象,分别测定其在贮藏过程中的脂肪氧化(硫代巴比妥酸)、蛋白质氧化(羰基值、总巯基、表面疏水性)和加工品质(失水率、蒸煮损失率、剪切力、质构特性)的变化。结果表明,不同贮藏温度和包装方式下的瘤胃均发生了不同程度的脂肪和蛋白质氧化,与薄膜包装相比,真空包装可延缓牦牛瘤胃脂肪和蛋白质氧化的发生,且-18℃冻藏下更为显著。此外,冷(冻)藏条件下不同包装牦牛瘤胃的失水率和蒸煮损失率均显著增大(P<0.05),剪切力值显著降低(P<0.05),硬度先减小后增大,且薄膜包装在冷藏0~5 d和冻藏0~28 d时,其加工特性均优于真空包装。综上表明,2种包装下的牦牛瘤胃在冷(冻)藏过程中均发生了脂肪和蛋白质氧化,但真空包装可以有效地延缓氧化反应的发生。此外,在冷藏0~5 d和冻藏0~28 d时,薄膜包装更有利于改善瘤胃的加工特性,增加其嫩度和弹性,但长时间贮藏会导致瘤胃加工特性下降,冷藏条件下薄膜包装瘤胃的变化表现最为显著。本研究可为瘤胃贮藏过程中食用品质的控制提供参考。     

不同土壤水分状况下遮蔽对棉花叶片气体交换的影响

An incubation experiment was carried out in laboratory to study the effect of temperature,moisture,phosphorus,organic matter,cropping and previous elemental sulfur application on elemental sulfur oxidation in four selected soils,fluvo-aquic soil,black soil,yellow-brown soil and red soil,In all the soils tested,sulfur oxidation rate was influenced by temperature and the temperature coefficient(Q10) values at the range from 10 to 30℃ were 4.41,,6.19 and 3.71 for the four soils,respectively.The rate of sulfur oxidation was parabolically related to soil water content.The optimum moisture content for the maximum oxiation rate was different among soils,Phosphorus increased the oxidation rate of elemental sulfur by 57.7%,33.1%,21.7% and 26.4% for the above four soils,respectively,compared with the control (no phosphorus applied).Organic material of corn straw which was gound and passed through a 0.5-mm sieve also increased th oxidation rate of elemental sulfur in the four soils by 59.8%,7.8%,39.2% and 540.4%,respectively.Elemental sulfur which was applied previously to soils significantly enhanced the oxidation of elemental sulfur subsequently added and increased sulfur-oxidizing populations such as autotrophic elemental sulfur oxidizers with pH optimum 6.8,autotrophic thiosufate oxidizers with pH optimum 6.8,heterotrophic thiosulfate oxidizers and heterotrophic sulfate producers.Cropping had little effect on elemental sulfur-oxidizing potentiality of soils.     

围垦对崇明东滩湿地全程氨氧化微生物的影响

全程氨氧化微生物（comammox）的发现根本改变了学术界对硝化过程的认识，但其地理分异规律及对氮转化过程的贡献仍不清楚。本研究选择长江口崇明东滩不同围垦年限（0、27、51、86年）稻田表层耕作土壤，采用好氧培养试验测定土壤硝化潜力；通过标靶功能基因amoA实时荧光定量硝化微生物的数量变异特征，包括全程氨氧化细菌（comammox）、氨氧化细菌（AOB）和古菌（AOA）。结果表明，与围垦0年的自然滩涂湿地相比，围垦27、51、86年的水稻土净硝化速率从2.24mg N /(kg·d)分别增加至19.3、11.6和11.4mg N /(kg·d)，增幅高达5.1-8.7倍。土壤氨氧化古菌AOA的丰度与围垦年限显著正相关。自然滩涂湿地中氨氧化古菌AOA和AOB的数量分别为0.34×107 copies/g和1.14×107 copies/g，围垦86年后增幅最高可达27.9倍。自然滩涂湿地中comammox Clade A和Clade B amoA基因拷贝数高于围垦稻田土壤，且Clade A随着围垦年限增加其丰度显著增加。统计分析发现，氨氧化细菌AOB与土壤硝化速率显著正相关，可能在围垦水稻土氨氧化过程中发挥了重要作用；而全程硝化细菌comammox Clade A和Clade B与土壤总有机碳（TOC）、铵含量（NH4+）呈显著负相关关系，可能更适应于营养贫瘠的滩涂自然湿地土壤。     

甲烷厌氧氧化微生物的研究进展

甲烷是一种重要的温室气体,其对全球气候变暖的贡献率约占20%。微生物进行的甲烷厌氧氧化(Anaerobic oxidation of methane,AOM)是减少自然环境中该温室气体排放的重要生物途径。根据耦联反应的不同,可将AOM分为两类,即硫酸盐还原型甲烷厌氧氧化(Sulphate-dependent anaerobic methane oxida-tion,SAMO)和反硝化型甲烷厌氧氧化(Denitrification-dependent anaerobic methane oxidation,DAMO),前者以SO42-作为AOM的最终电子受体,后者以NO2-/NO3-作为AOM的最终电子受体。深入了解这两种类型AOM的发生机理,有助于更好地理解该生物过程的重要性,为AOM工艺的开发提供理论依据。鉴此,本文简要介绍了不同类型的AOM及其参与的微生物,着重阐述了其发生机理,并探讨了AOM未来的研究方向与应用前景。     

Micro nutrient toxicity in French marigold

The influence of elevated levels of micronutrients on the growth and flowering of French marigold (Tagetes patula L.) was investigated. Plants were grown with nutrient solution containing 0.25, 0.5, 1, 2, 3, 4, 5, or 6 mM boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn) and toxicity development was monitored. The threshold micronutrient concentrations that induced visible foliar toxicity symptoms were 0.5 mM B, 4 mM Cu, 4 mM Fe, 2 mM Mn, 1 mM Mo, and 5 mM Zn. The dry matter yields during the 5 week experimental period were reduced when micronutrient concentrations exceeded 0.5 mM B, 3 mM Cu, 3 mM Fe, 6 mM Mn, 0.5 mM Mo, and 5 mM Zn in the fertilizer solution. Leaf chlorophyll contents decreased when the nutrient solution concentrations of Cu, Fe, and Mn were greater than 0.5 mM, 3 mM, and 2 mM, respectively. Visual toxicity symptoms of the six micronutrients were characterized.     

Modes of action of nitrification inhibitors

 In recent years, substantial progress has been made towards understanding the modes of action for the specific inhibition of autotrophic NH₃ oxidation. This has included demonstrating that NH₃ monooxygenase (AMO) has a broad substrate range for catalytic oxidation, and the inhibitory effects of many compounds are due to competition for the active site. Other compounds, such as acetylenes, are oxidized by the normal catalytic cycle of AMO to highly reactive products which covalently bind the enzyme causing irreversible inhibition. Substantial evidence has shown the important role of Cu in the activity of AMO, and indicated that a large class of compounds containing thiono-S inhibit AMO activity by binding with Cu within the active site. Heterocyclic N compounds form another important class of nitrification inhibitors with little known about their mode of action, although evidence suggests that their inhibitory influence is closely related to the presence of ring N. Received: 21 July 1998     

Microbial ethylene production and inhibition of methanotrophic activity in a deciduous forest soil

Production of C₂H₄, but not of CH₄, was observed in anoxically incubated soil samples (cambisol on loamy sand) from a deciduous forest. Ethylene production was prevented by autoclaving, indicating its microbial origin. Ethylene production gradually decreased from 4 to 12 cm soil depth and was not affected by moisture or addition of methionine, a possible precursor of C₂H₄. Oxidation of atmospheric CH₄ in soil samples was inhibited by C₂H₄. Ethylene concentrations of 3, 6 and 10 μl l⁻¹ decreased CH₄ uptake by 21, 63 and 98%, respectively. Methionine and methanethiol, a possible product of methionine degradation, also inhibited CH₄ oxidation. Under oxic conditions, C₂H₄ was consumed in the soil samples. Ethylene oxidation kinetics exhibited two apparent K_m values of 40 μl l⁻¹ and 12,600 μl l⁻¹ suggesting the presence of two different types of C₂H₄-oxidizing microorganisms. Methanotrophic bacteria were most probably not responsible for C₂H₄ oxidation, since the maximum of C₂H₄ oxidation activity was localized in soil layers (2-8 cm depth) above those (8-10 cm depth) of CH₄ oxidation activity. Our observations suggest that C₂H₄ production in the upper soil layers inhibits CH₄ oxidation, thus being one reason for the localization of methanotrophic activity in deeper soil layers.     

Short-term kinetic response of enhanced methane oxidation in landfill cover soils to environmental factors

 This paper aims at a better understanding of methane oxidation under conditions that are representative of landfill cover soils. The kinetics of methane oxidation were studied in landfill cover soils that had been exposed to high methane mixing ratios. This was done in batch experiments, under various environmental conditions. V _max increased exponentially with temperature in the range 5–35  °C, with a Q ₁₀ value of 2.8. K _m increased approximately linearly in this range from 1.2 μM to 7 μM. Consequently, the influence of temperature on methane consumption was more pronounced at high concentrations than at low concentrations. The inhibition by ammonium of methane consumption was much stronger after 6–7 months of exposure to high methane mixing ratios than after 5–7 weeks of exposure, indicating that there was a shift of dominating methanotrophic species in soils after long exposure times. Additions of nitrifying sludge or compost to soils initially inhibited methane oxidation, followed by a stimulation after a few days. Received: 19 May 2000