Effect of copper on phospholipid fatty acid composition of microbial communities in two red soils

The phospholipid fatty acid （PLFA） composition was analyzed in two red soils experimentally contaminated with copper at different concentrations. The total amounts ofphospholipid fatty acids （PLFAs） in both red soils were significantly correlated with soil microbial biomass C and N, which decreased consistently with increasing levels of copper. The relative quantities of the PLFAs 17：0 （10 Me）, i16：0, il 5：0 and 16：1w5c, decreased with increasing heavy metal concentration, while those of cyl7：0, which is an indicator of gram-negative bacteria, increased. The Shannon index calculated from the PLFA data indicated that Cu addition in the red soils decreased the population diversity of soil microbial communities. Multivariate analysis of PLFA data demonstrated that high levels of Cu application had a significant impact on microbial community structure and there is a threshold metal concentration for PLFA composition. Comparatively higher toxic effect on microbial biomass and community structure were found in the red sandy soil than those in the red clayey soil. The differential effect of Cu addition on microbial communities in the two soils may be due to differences in soil texture and cation exchange capacity.

Using Phospholipid FattyAcid Technique toAnalysis the Rhizosphere Specific Microbial Community of Seven Hybrid Rice Cultivars

To analyze the intrinsic relationship between rhizosphere microbial community structure and variety of rice, the microbial community structures in rhizosphere of different hybrid rice cultivars were determined with phospholipid fatty acids （PLFA） analysis. Three series of new-breeding hybrid rice cultivars in China were tested in the experiment, Ilyouming 86 （II-32A/Minghui 86）, Ilyouhang 1 （II-32A/Hang 1）, and Ilyouhang 2 （II-32A/Hang 2） with H-32A as female parent, XinyouHK02 （XinA/HK02） and YiyouHK02 （YXA/HK02） with HK02 as male parent, Chuanyou 167 （ChuanxiangA/MR167） and 44you167 （Hunan44A/MR167） with MR167 as male parent. The results showed that the microbial community in rhizosphere of the hybrid rice comprised bacteria, fungi, actinomycetes, and protozoa, according to the 40 PLFA biomarkers detected. Bacteria were more abundant than fungi and actinomycetes in rhizosphere of the hybrid rice tested. Both sulfate-reducing and methane-oxidizing bacteria were found to exist in the hybrid rice rhizosphere. It was also found that the characteristics of PLFA biomarkers had correlation with the biological traits of rice. The cluster analysis suggested that microbial community structure and activity in rhizosphere were associated with genetic background of the rice cultivar.

Phospholipid Fatty Acid Profiles of Chinese Red Soils with Varying Fertility Levels and Land Use Histories

Analysis of phospholipid fatty acids (PLFAs) was used to estimate the microbial community structures of eight Chinese red soils with different fertility levels and land use histories. The total amounts of PLFAs in the soils were significantly correlated with soil organic carbon, total nitrogen, microbial biomass C and basal respiration, indicating that total PLFA was closely related to fertility and sustainability in these highly weathered soils. Soils for the eroded wasteland were rich in Gram-positive species. When the eroded soils were planted with citrus trees, the soil microbial population had changed little in 4 years but took up to 8-12 years before it reached a significantly different population. Multivariate analysis of PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure. However, the difference of soil microbial community structure in the paddy field compared to other land uses was not larger than expected in this experiment.

Long-Term Effects of Docosahexaenoic Acid-Bound Phospholipids and the Combination of Docosahexaenoic Acid-Bound Triglyceride and Egg Yolk Phospholipid on Lipid Metabolism in Mice

The bioavailability of docosahexaenoic acid(DHA) and eicosapentaenoic acid(EPA) depends on their chemical forms. This study investigated the long-term effects of DHA-bound triglyceride(TG-DHA), DHA-bound phospholipid(PL-DHA), and the combination of TG-DHA and egg yolk phospholipid(Egg-PL) on lipid metabolism in mice fed with a high-fat diet(fat levels of 22.5%). Male C57BL/6J mice were fed with different formulations containing 0.5% DHA, including TG-DHA, PL-DHA, and the combination of TG-DHA and Egg-PL, for 6 weeks. Serum, hepatic, and cerebral lipid concentrations and the fatty acid compositions of the liver and brain were determined. The concentrations of serum total triglyceride(TG), total cholesterol(TC), high-density lipoprotein cholesterol(HDL-c), and hepatic TG in the PL-DHA group and the combination group were significantly lower than those in the high-fat(HF) group(P < 0.05). Atherogenic index(AI) of the PL-DHA group was significantly lower than that of the combination group(P < 0.05). Hepatic TC level in the combination group was significantly lower than that in the HF group(P < 0.05), but no significant difference was observed between the combination group and the PL-DHA group. Both the PL-DHA and the combination groups showed significantly increased DHA levels in the liver compared with the HF group(P < 0.05). However, there were no obvious increases in the cerebral DHA levels in all DHA diet groups. These results suggest that PL-DHA was superior to the combination of TG-DHA and Egg-PL in decreasing the AI. Long-term dietary supplementation with low amount of DHA(0.5%) may improve hepatic DHA levels, although cerebral DHA levels may not be enhanced.

Temperature-Dependent Fatty Acid Composition Change of Phospholipid in Steelhead Trout (Oncorhynchus mykiss) Tissues

In this study, the changes of the fatty acid composition of phospholipid in different tissues(muscle, heart, brain and spleen) of steelhead trout(Oncorhynchus mykiss) were analyzed when the water temperature decreased gradually from 16 to 12℃℃, 8℃, 6℃, 4℃, 2 and 1℃℃. Three fish individuals each tank(average weight 70.32 g ± 9.12 g) were collected and used to analysis at each designed temperatures. At normal temperature(16℃), the fatty acid composition of phospholipid of muscle and heart was similar each other. The highest concentration of saturate fatty acids(SFA) was found in the phospholipid of spleen. The brain phospholipid contained higher oleic acid(18:1 n9) than the phospholipid of other tissues at 16℃. When the environmental temperature decreased, the concentration of unsaturated fatty acids of phospholipids in all tissues increased, and accordingly the ratio pf the unsaturated to saturated fatty acids(U/S) and unsaturation index(UI) increased, indicating that steelhead trout can compensate temperature-dependent changes in membrane fluidity by remodeling the fatty acid composition of phospholipids. The changes in the fatty acid composition of phospholipid were tissue-specific. At the early stages of the experiment(16 to 8℃℃), the fatty acid composition of phospholipid changed remarkably in muscle, heart, and spleen. When temperature decreased to less than 8℃, an obvious response of phospholipid fatty acid was observed in all tissues. The change of phospholipid composition of steelhead trout tissues may be affected by both cold stress and starvation when the temperature decreased to 2℃, and the change of phospholipid composition of muscle was very obvious.

The effect of high fat food on erythrocyte phospholipids, fatty acids composition and glutathione redox-system of rats with alimentary dyslipidemia

To evaluate the effects of high fat food consisted of tallow (19% of total diets) and cholesterol (2%) on modification of erythrocyte phospholipids, fatty acids composition and glutathione redox- system of male Wistar rats with alimentary dysli- pidemia. The results demonstrated that after 30 and 180 days of high-fat feed erythrocyte phos- phatidylinositol and phosphatidylcholine levels were reduced, phosphatidylserine were in-creased. Only on the 90 days of the experiment phosphatidylinositol level increased. In all grow- ups the erythrocyte 18:0 saturated fatty acids and 20:4n6, 22:4n6 polyunsaturated fatty acids (PUFA) were increased. Deficit of n3 PUFA- 20:5n3 and 22:6n3 after 90 and 180 days high fat feed promoted compensatory synthesis from 18:1n9 on 20:3n9. Erythrocyte maleic dialde-hyde increased, glutathione level decreased in all groups of rats after fed with high-fat feed. Glutathione reductase and glutathione peroxi-dase activity decreased in erythrocytes after 30 and 180 days of high-fat feed. In conclusion: high-fat diet during 30-90 days started adaptive answer in lipids of membrane and glutathione redox-system. Important mechanism of adapta-tion of a cellular membrane to high-fat diet is increase major, structuring a membrane phos-phatidylethanolamine and minor, most meta-bolic significant fractions phospholipids (phos- phatidylinositol), keeps homeostasis of 18:2n6 and 22:6n3, 20:3n9 compensatory synthesis, decrease in activity of processes lipid peroxi-dation, activation of enzymes of redox-system glutathione. But prolonging the high-fat feeding (180 days and more) formed failure compensa-tory processes (dysadaptation). It is a risk factor of developmening atherosclerosis, diabetes, steatogepatitis and other diseases.

Olive and Corn Oil Enriched Diets Changed the Phospholipid Fatty Acid Composition in Mice Liver after One-Thirds Hepatectomy

We examined the effect of dietary fats on the kinetics of liver regeneration after one-third partial hepatectomy (PH) in male Balb/c mice. Corn and olive supplemented diets were chosen as a model of n-6 and n-9 diets. Phospholipid fatty acids were determined by gas chromatography (GC) after previous fractionation by solid-phase extraction using aminopropyl (NH2) column, and data were analysed by nonparametric Kruskal-Wallis test. Diet enriched with corn and olive oil did not affect the balance of lipid disorders during liver regeneration after 1/3 PH. Desaturases activity direction has changed depending on the used diet. The key role in the alteration of the polar fatty acids profile at all stages of liver regeneration and examined dietary fats is played by activity of stearoyl-CoA desaturase (SCD).

Comparison of the fatty acid composition of the serum phospholipids of controls, prediabetics and adults with type 2 diabetes

Objective: Although abnormalities in the fatty acid composition of serum and red cell membrane phospholipids of patients with type 2 diabetes are well-documented, lacking are studies of this issue in prediabetic individuals. Materials/Methods: For this cross-sectional study, we recruited 180 subjects (30 - 80 years), 56 of whom were normal with regard to glucose control (HbA1c, 6.5%). Serum phospholipids were isolated and analyzed for fatty acids. Results: Most importantly, the fatty acid compositions of the controls and prediabetic subjects were not different for 19 fatty acids. However, the fatty acid profile of the phospholipids of the patients with diabetes differed from the other two groups;the 14 to 18-carbon saturated fatty acids were decreased by 12% - 26% whereas the unsaturated fatty acids 16:1n-7, 18:1n-9, 18:2n-6, 20:3n-6 and 20:4n-6 were increased by 45% - 64%. Of note, the docosahexaenoic acid (DHA) status of individuals in all three study groups was remarkably low compared with international values, as indicated by DHA proportions in the 1.62% - 2.07% range, and there were no differences between groups. The mean melting point of the phospholipid fatty acids of the diabetic patients (32.2℃) was significantly lower (p < 0.001) than that of the prediabetic subjects (38.1℃) and the controls (39.9℃) which were not different from each other. Conclusion: These observations indicate that the fatty acid changes associated with type 2 diabetes follow the onset of the disease as opposed to being a causative factor of poor glucose control and insulin insensitivity.

Plasma Phospholipid Omega-3 Fatty Acids and Freshwater Fish Consumption in the Brazilian Amazon

Background: Amazonian riverside communities consume large quantities of freshwater fish, comparable to marine fish consumption of Inuit, Scandinavian and Japanese populations. Few studies have considered the relation of high freshwater fish consumption and intake of omega-3 fatty acids (FA). Objective: The objective of the present study was to determine the profile of the concentrations of plasma phospholipid FAs and its relation with freshwater fish intake in 12 riverside communities in the Tapajós River basin (State of Pará, Brazilian Amazon). Design: This cross-sectional study included 333 adults (15 - 86 years old). Fish meal frequency was determined using a 7-day interview-administered dietary recall questionnaire. Fish were categorized as piscivorous and non-piscivorous fish on trophic level. Plasma phospholipid FAs were measured by capillary gas-liquid chromatography. Results: Participants consumed 5 to 6 fish meals a week, with twice as many non-piscivorous fish than piscivorous fish (4.4 fish/week vs 2.2 fish/week, respectively). The omega-3 FA levels in plasma phospholipids were low (EPA + DHA = 31.21 mg/L;%EPA + DHA = 2.59%). Omega-3 FAs increased with frequency of fish intake, and particularly with piscivorous fish, controlling for sociodemographic, anthropometric and lifestyle characteristics. DHA levels were greater in women than in men. Conclusions: Omega-3 FA in this Amazonian population increased with fish consumption, but although they consumed freshwater fish almost daily, the concentrations of omega-3 FA were relatively low and comparable to fish-eater communities for which fish is not a dietary mainstay. It is possible that nutrients present in marine, but not in certain freshwater fish species, may facilitate absorption of omega-3 FA. Sex and/or gender differences must be taken into account when assessing the relationship between fish consumption and plasma phospholipid omega-3 FA levels.

Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory(Carya cathayensis Sarg.)is an important economic forest in Southeastern China.A large amount of hickory husk waste is generated every year but with a low proportion of returning.Meanwhile,intensive management has resulted in soil degradation of Chinese hickory plantations.This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment,including soil acidity,soil nutrition,and microbial community.The field experiment carried out four treatments:control(CK),hickory husk mulching(HM),hickory husk biochar(BC),and hickory husk organic fertilizer(OF).The phospholipid fatty acid(PLFA)biomarker method was employed to determine the soil microbial community.After one year of treatment,the results showed that:(i)HM and BC significantly increased soil pH by 0.33 and 1.71 units,respectively;(ii)HM,BC and OF treatments significantly increased the soil organic carbon,alkaline nitrogen,available phosphorous,and available potassium.The OF treatment demonstrated the most significant improvement in the soil nutrient;(iii)The soil microbial biomass significantly increased in the HM,BC and OF treatments,and all microbial groups showed an increasing trend.HM treatment increased the fungal/bacterial ratio(F/B).The OF treatment significantly decreased the Shannon-Wiener diversity(H’)and evenness index(J)of the microbial community(P<0.05).Considering the treatments effects,costs,and ease of operation,our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.

Effects of Dietary Phospholipids on Na^+-K^+-ATPase Activity and Cell Membrane Fatty Acid Composition in Gill of Catfish (Pangasius sutchi)

[ Objective] The aim of this study was to determine the effects of dietary phospholipids on Na＋ - K＋ - ATPase activity and cell mem- brane fatty acid composition in the gill of catfish （Pangasius sutchi）. [Method] 900 healthy catfish （1.4 ±0.08 g of average weight） were randomly divided into five groups. Dietary phospholipids level of group PL0 was 0%, and 1%, 2%, 3%, 4% for group PL1, PL2, PL3, PL4, respectively. The experiment lasted for 56 days. [Result] The results showed that the Na＋ -K＋ -ATPase activity in gill decreased gradually with the increase of the dietary phospholipids level （ P 〈0.05）. Cell membrane fatty acid composition was affected significantly by dietary phospholipids. The content of saturated fatty acids and monounsaturated fatty acids of group PLO was the highest （ P 〈 0.05）, however, it had the lowest content of highlyunsatu- rated fatty acids （ P 〈 0.05）. The content of polyunsaturated fatty acids of group 3 was higher than group 0 and group 1 （ P 〈 0.05）. E Conclusion] The results indicated that there is obvious compensation effects on Na＋ -K＋ -ATPase activity with phospholipids content changes in gills of catfish （ Pangasius sutchi） to maintain stable physiological level and normal basal metabolism and the increase of HUFA and ∑PUFA is necessary for gill cell membrane to better maintain and perform normal physiological function.

林分改变驱动的优势菌根真菌类型变化影响土壤有机碳积累

马尾松林(PinusmassonianaLamb.)是典型的外生菌根(Ectomycorrhiza,ECM)优势林,但是近年来受到松材线虫病的影响,生态服务功能下降,逐渐被丛枝菌根(Arbuscularmycorrhiza,AM)占优势的阔叶林所替代,但亚热带地区马尾松林转变为阔叶林过程中,优势菌根类型的改变对土壤有机碳积累的影响仍不清楚。以建德市马尾松林和阔叶林为研究对象,通过高效液相色谱和中性脂肪酸、磷脂脂肪酸等技术,测定优势菌根真菌生物量、球囊霉素相关土壤蛋白(GRSP)含量以及土壤胞外酶活性和微生物群落特征。结果表明:AM真菌占优势的阔叶林(AMD)取代ECM真菌占优势的马尾松林(ECMD),土壤有机碳显著提高了36.81%,微生物碳利用效率(CUE)显著提高了53.85%,AM真菌生物量提高了25.57%,ECM真菌生物量下降45.04%,并且ECM真菌占优势的马尾松林受到更严重的氮限制。磷脂脂肪酸分析显示,相比于AM真菌占优势的阔叶林,ECM真菌占优势的马尾松林革兰氏阳性细菌(G^(+))以及革兰氏阳性与阴性细菌之比(G^(+)/G^(–))分别显著下降了21.47%和6.46%。冗余分析(Redundancy analysis,RDA)结果表明,AM真菌占优势和ECM真菌占优势的森林之间土壤微生物群落结构存在显著差异(P<0.05),其中AM真菌生物量和土壤有机碳与微生物群落结构变异显著相关。GRSP含量下降以及不同类型菌根真菌招募微生物类群不同是导致ECM真菌占优势森林土壤有机碳下降的重要原因。因此,亚热带地区马尾松林被阔叶林替代后增加森林土壤有机碳含量,提高森林碳汇功能。

膨腹海马脂质及其脂肪酸组成分析

为揭示雌、雄膨腹海马的脂质成分,该研究采用改良后的Folch法分别提取雌、雄海马总脂并解析其基本脂质组成;采取薄层层析法分离并制备不同的脂质成分,通过气相色谱技术比较分析各脂质成分的脂肪酸组成差异。试验结果显示:膨腹海马的脂质含量丰富,雌、雄海马总脂含量分别为57.8、65.8 mg/g干重,且以磷脂、游离脂肪酸为主,甘油三酯、胆固醇含量较低,除胆固醇含量雄性明显高于雌性以外,其他成分雌雄几乎无区别;雌、雄海马总脂脂肪酸组成接近,不饱和脂肪酸含量均高于饱和脂肪酸,且海洋特征性n-3多不饱和脂肪酸二十二碳六烯酸(docosahexaenoic acid,DHA)、二十碳五烯酸(eicosapentaenoic acid,EPA)含量超过18%;不同脂质组分中,甘油三酯、磷脂、游离脂肪酸主要含有饱和脂肪酸,而胆固醇酯则以单不饱和脂肪酸为主。

酵母磷脂的制备与组分分析

酵母磷脂是从酵母中提取的磷脂类混合物,是全新的磷脂来源,具有重要的研究价值。文章以酿酒酵母CCTCC M2016418为原料,通过对提取溶剂筛选,不同料液比和混合溶剂萃取优化,建立了酵母磷脂提取和制备工艺,并与大豆磷脂组分进行了比较。结果显示,采用料液比为1∶10(g∶mL),乙醇与石油醚依次萃取的方法,最高酵母磷提取率为31.09%。组分分析表明大豆磷脂中磷脂酰胆碱和多不饱和脂肪酸质量分数是酵母磷脂的2.19倍和13.67倍,酵母磷脂中磷脂酰乙醇胺和单不饱和脂肪酸质量分数是大豆磷脂的1.45倍和1.27倍,预示2种磷脂不同的应用效果。

辛酸结构大豆磷脂酶法改性工艺优化

为了改善天然磷脂的理化性质以及拓宽其应用范围,以辛酸和大豆磷脂为底物,采用酶法对大豆磷脂进行改性。筛选了改性大豆磷脂的脂肪酶,考察了反应温度、反应时间、脂肪酶用量、底物质量比对辛酸结构大豆磷脂改性工艺的影响,在此基础上,采用正交试验优化大豆磷脂的酶法改性工艺条件,并考察了脂肪酶的重复利用性。结果表明:Novozym 435脂肪酶的催化效果优于Lipozyme RM IM和Lipozyme TL IM;大豆磷脂酶法改性的最优条件为反应温度55℃、Novozym 435用量25%、底物质量比(辛酸与大豆磷脂质量比)7∶1、反应时间36 h,在此条件下辛酸结合率可达(78.79±0.81)%;Novozym 435经过4次重复利用后,辛酸结合率仍能达到(63.67±1.50)%。综上,Novozym 435可作为催化磷脂改性的优选脂肪酶。

长期不同施肥措施对盐碱地稻田土壤微生物数量和群落结构的影响

为阐明盐碱地稻田长期不同施肥对表层土壤微生物数量和群落结构的影响,以大安站盐碱地水稻长期定位施肥试验土壤为对象,采用磷脂脂肪酸(PLFA)分析法研究了单施氮肥(N)、无机肥配施(NPK)、有机肥单施(M)、有机肥与无机肥配施(MNPK)和秸秆还田配施无机肥(RNPK)对土壤微生物数量和群落结构的影响。结果表明:不同施肥处理土壤中共检测出57种PLFA生物标记,M、MNPK、RNPK和NPK处理的PLFA含量较N处理分别增加26.47%、29.76%、25.07%和13.20%,其中M、MNPK和RNPK处理显著高于N处理(P<0.05)。MNPK处理土壤中的真菌/细菌的比值最大,较二者之比最小的M处理高6.00%,说明有机肥配施化肥对盐碱地稻田土壤生态系统的稳定性具有更好的改善作用。RNPK处理土壤中革兰氏阳性菌与革兰氏阴性菌之比最小,较二者之比最大的M处理降低了13.71%,说明秸秆还田配施化肥处理的土壤营养胁迫小,能有效改善土壤的营养状况。不同施肥处理微生物群落多样性大小表现为N处理土壤的Shannon-Wiener多样性指数(H)、Pielou均匀度指数(J)和Simpson优势度指数(D)最大,分别较3项指数最小的NPK处理增加10.91%、12.00%和13.79%。冗余分析结果表明,盐分电导率(EC)、有机质和pH对土壤微生物群落变化具有显著影响,解释量分别为54.8%、39.8%和33.1%。因此,长期有机肥与化肥配施、有机肥单施和秸秆还田配施无机肥能有效增加土壤微生物生物量并优化微生物群落结构,进而改善土壤生态环境。

草原苏尼特羊脑中磷脂型DHA萃取及其结构特性研究

旨在为绿色天然草原羊脑中磷脂型二十二碳六烯酸(DHA-PL)的开发利用提供科学数据,以苏尼特冻干羊脑为原料,采用溶剂萃取其中的粗脂肪,用冰丙酮沉淀得到磷脂,再采用硅胶柱层析法分离其中的磷脂酰胆碱(PC)和磷脂酰丝氨酸(PS)。测定了粗脂肪中胆固醇含量,以及磷脂中PC和PS的含量,分析了粗脂肪、磷脂、PC和PS中DHA含量,以及PC和PS中sn-2位的DHA含量。结果表明:采用体积比2∶1乙醇-正己烷萃取冻干苏尼特羊脑中粗脂肪,粗脂肪得率较高,为45%;羊脑粗脂肪中胆固醇含量为29.42mg/g,粗脂肪的脂肪酸组成中DHA含量为8.89%;磷脂的脂肪酸组成中DHA含量为11.41%;磷脂中PC和PS含量分别为27.67μg/g和10.69μg/g,PC和PS的sn-2位脂肪酸组成中DHA含量分别为8.06%和2.59%。综上,可以从苏尼特羊脑中制备易于吸收的DHA-PL。

云南金沙江干热河谷土壤微生物群落结构特征及影响因素

金沙江干热河谷区是长江上游重要的生态屏障和典型生态脆弱区,对金沙江干热河谷土壤微生物群落结构变异特征及其驱动因素的了解仍不清楚。沿着金沙江选择5个地点的典型干热河谷植被,采用磷脂脂肪酸法研究了土壤微生物生物量和群落结构的空间变异,并探讨了气候、植被因子和土壤性质等对土壤微生物群落结构的影响。结果表明:不同研究点土壤总微生物生物量介于4.30—13.20 nmol/g,以细菌为主,其中革兰氏阳性菌(G+)占26.22%—33.65%,革兰氏阴性菌(G-)占18.35%—23.67%;真菌占9.02%—15.13%。不同研究点土壤微生物生物量、真菌/细菌和G+/G-差异显著,并且非度量多维尺度分析形成不同聚类,表明土壤微生物群落结构在研究点间发生了变化。方差分解结果揭示了土壤微生物群落结构的变异主要受土壤因子的驱动,其次是植被和气候因素。草本生物量、土壤硝态氮、全碳、pH和含水量对土壤微生物群落结构具有显著影响。气候因素中年均降雨量对微生物生物量呈负影响效应。揭示了不同研究点通过土壤性质驱动了土壤微生物群落结构的变异,并发现了草本生物量在其中的重要作用,对干热河谷区植被恢复具有重要的意义。

福建海岸沙地5种防护林土壤微生物群落特征

[目的]探明福建海岸沙地不同防护林对土壤微生物群落的影响及机制,为海岸带防护林森林质量提升提供科学依据。[方法]选择5种主要防护林为对象,分别为次生林、木麻黄(Casuarina equisetifolia)人工林、湿地松(Pinus elliottii)人工林、厚荚相思(Acacia crassicarpa)人工林和尾巨桉(Eucalyptus urophylla×E.grandis)人工林,采用磷脂脂肪酸法(Phospholipids fatty acid, PLFA)比较了不同防护林的土壤微生物群落结构。[结果](1)海岸沙地不同防护林土壤中共检测到18种PLFA生物标记,在尾巨桉和次生林中种类最多,湿地松和厚荚相思人工林最少。(2)土壤总磷脂脂肪酸、革兰氏阳性细菌和革兰氏阴性细菌含量均表现为尾巨桉和次生林较高,厚荚相思和木麻黄人工林较低,土壤真菌含量为尾巨桉林最高,丛枝菌根菌含量为次生林最高,真菌和丛枝菌根菌含量在其他防护林间无显著差异。(3)次生林的土壤微生物多样性和均匀度均高于4种人工林。(4)土壤pH、细根碳氮含量为土壤微生物群落的主要影响因子,其次为土壤全氮和硝态氮含量以及凋落物木质素/氮和细根碳氮比。[结论]不同防护林对土壤微生物群落的影响存在显著差异,在海岸带木麻黄防护林中引种尾巨桉和乡土树种,可以增加土壤微生物多样性,提高森林生态功能。

芝麻脱皮对芝麻香油自然沉降过程的影响

在芝麻香油精制过程中,自然沉降规律受诸多因素影响,为探索提升芝麻香油精制效率的技术手段,以脱皮和未脱皮芝麻所得芝麻香油为研究对象,通过测定芝麻原油与沉淀物组成,并结合沉降过程中沉淀物含量、磷脂含量、酸值、过氧化值、沉淀物压缩速度的变化规律,考察芝麻脱皮对芝麻香油自然沉降过程的影响。结果表明:相比未脱皮芝麻香油,脱皮芝麻香油在线性沉降阶段的沉降效率高约5百分点;芝麻香油沉淀物的90%以上是粗脂肪,还有少量水分、磷脂、蛋白质、糖形成的胶杂,水和磷脂发生明显聚集;沉淀物的酸值远高于芝麻香油,但过氧化值变化不明显;芝麻香油磷脂含量与沉淀物含量变化呈现相似的趋势,上、下层油中磷脂含量和酸值在线性沉降阶段后差异较小;脱皮芝麻香油沉淀物初始高度远低于未脱皮芝麻香油,且在线性沉降阶段压缩速度快于未脱皮芝麻香油,最终成品油得率高于未脱皮芝麻香油约3百分点。综上,脱皮有利于芝麻香油的自然沉降以及获得更高的得率。