Assessment of antioxidant activity of cane brown sugars by ABTS and DPPH radical scavenging assays: determination of their polyphenolic and volatile constituents

Seven cane brown sugars (four from La Réunion, two from Mauritius, and one from France) were investigated for their polyphenol content and volatile composition in relation to their free radical scavenging capacity determined by ABTS and DPPH assays. The thin layer coated on the sugar crystal was extracted by Soxhlet extractor with dichloromethane. The volatile compounds of brown sugars were studied by GC-MS, and 43 compounds were identified. The total phenolic content of brown sugars was determined according to the Folin-Ciocalteu method. Phenolic compounds were quantified in the brown sugar extracts by LC-UV-ESI-MS. Brown sugar aqueous solutions exhibited weak free radical scavenging activity in the DPPH assay and higher antioxidant activity in the ABTS assay at relatively high concentration. The brown sugar extracts showed interesting free radical scavenging properties despite the low concentration of phenolic and volatile compounds. Sugar is a common foodstuff traditionally used for its sweetening properties, which might be accompanied by antioxidant properties arising from molecules (polyphenols, Maillard products) other than sucrose of the cane brown sugars.     

Transformation of organic rhizodepositions by rhizosphere bacteria and its influence on the availability of tertiary calcium phosphate

This study assesses the influence of saccharides in the rhizodeposition on the phosphate solubilizing ability of rhizosphere bacteria. Water‐soluble rhizodeposits were analyzed of ¹⁴C‐labeled pea plants (Pisum sativum, cv. ‘Grapis’) which were grown at two different levels of P‐nutrition. The sugars produced were fed in vitro either as single compounds or as synthetic mixtures to three bacterial strains and the ability of the bacteria to mobilize Ca₃(PO₄)₂ was measured. The relative glucose proportion of pea exudates decreased under P deficiency while the content of galactose, ribose, xylose and fucose increased. In vitro feeding of single sugars and sugar mixtures showed that the ability of Pseudomonas fluorescens (PsIA12) to dissolve tertiary calcium phosphate was lower with pentoses and the mixed sugars of the P‐deficient plants than with glucose. On the other hand, the shifted sugar pattern observed under P deficiency increased the phosphate mobilization ability of Pantoea agglomerans (D5/23) and Azospirillum sp. (CC 322) considerably. This observation can only partly be explained by the acidification of the nutrient medium. Bacteria also produced different carboxylic anions depending on sugar supply. In addition to low‐molecular mono‐, di‐, and tricarboxylic acids which are known as P‐solubilizing substances, sugar acids also played an important role in cultures D 5/23 and CC 322.     

Anthocyanin glycosides from berry fruit are absorbed and excreted unmetabolized by both humans and rats

Anthocyanins, the red/blue pigments found in plants, are polyphenolic compounds consumed by humans and are part of a normal diet. Recent studies have shown that anthocyanins have substantial bioactivity including antioxidant activity and therefore may have beneficial effects on human health. Anthocyanins are a group of over 500 compounds of diverse structures containing different core phenolic aglycons and conjugated with sugars in a variety of glycosylation patterns. In this study, we have investigated the bioabsorption of 15 anthocyanins with structures containing different aglycons and conjugated sugars extracted from blueberry, boysenberry, black raspberry, and blackcurrant in both humans and rats. Intact and unmetabolized anthocyanins were detected in urine of rats and humans following dosing for all molecular structures investigated, thus demonstrating that anthocyanins with diverse molecular structure and from different dietary sources are bioavailable at diet relevant dosage rates. In addition, the relative concentrations of anthocyanins detected in urine following dosing varied, indicating that differences in bioavailability are due to variations in chemical structure. Our results suggest that the nature of the sugar conjugate and the phenolic aglycon are both important determinants of anthocyanin absorption and excretion in rats and humans.     

The extraction and characterization of soil polysaccharide by whole soil methylation

A soil of the Countesswells series was repeatedly methylated by the Hakomori procedure and a chloroform-soluble product isolated after each methylation. Ninety-two per cent of the material engendered by seven methylations was released during the first four methylations. This had a methoxyl content of about 20% and contained 2% N. Later fractions had lower methoxyl and N contents. Residual carbohydrate in the soil had reducing sugar content on hydrolysis, equivalent to about 3% of the original value. The extracted material had the infrared spectrum of a methylated soil polysaccharide and, on hydrolysis by 2 m trifluoracetic acid, released methylated sugar derivatives of which 68 were characterised by GC-MS. Derivatives corresponding to (1→4) linked sugars predominated for both hexose and pentose sugars but there was also a large proportion of (1→3) linkages, (1→3) linkages predominated for the deoxyhexose sugars. There were more sugars with only one or two methylated hydroxyl groups than could be accounted for as branching points because of the relatively small numbers of end groups. Prior reduction of the soil with sodium borohydride had no measurable effect on the nature or yield of the methylated product. This indicates that amino acid sugar linkages susceptible to β-elimination reactions can have only a very small influence on the reaction. The isolated sugar derivatives accounted for 70% of the total soil sugars. The methylated material before hydrolysis had a low nominal molecular weight on diafiltration, with 68% < 10000. Some of the sugars unaccounted for were probably lost during the dialysis stage necessary to remove dimethyl sulphoxide.     

Effect of food models and low-temperature storage on the adhesion of Lactobacillus rhamnosus GG to Caco-2 cells

This study evaluated the effects of fat and sugar levels on the surface properties of Lactobacillus rhamnosus GG during storage in food model systems, simulating yogurt and ice cream, and related them with the ability of the bacterial cells to adhere to Caco-2 cells. Freeze-dried L. rhamnosus GG cells were added to the model food systems and stored for 7 days. The bacterial cells were analyzed for cell viability, hydrophobicity, ζ potential, and their ability to adhere to Caco-2 cells. The results indicated that the food type and its composition affected the surface and adhesion properties of the bacterial cells during storage, with yogurt being a better delivery vehicle than ice cream in terms of bacterial adhesion to Caco-2 cells. The most important factor influencing bacterial adhesion was the storage time rather than the levels of fats and sugars, indicating that conformational changes were taking place on the surface of the bacterial cells during storage.     

Evaluation of the site specific protein glycation and antioxidant capacity of rare sugar-protein/peptide conjugates

Protein-sugar conjugates generated in nonenzymatic glycation of alpha-lactalbumin (LA) with rare sugars [D-allose (All) and D-psicose (Psi)] and alimentary sugars as controls [D-glucose (Glc) and D-fructose (Fru)] were qualitatively determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Mass spectra revealed that the extent of glycation at lysine residues on LA with D-aldose molecules was very much higher than that of glycation with d-ketose molecules. To identify the specific site of glycation, the peptide mapping was established from protease V8 digestion, using a combination of computational cutting of proteins and MALDI-TOF-MS. As compared to peptide mapping, three and seven glycation sites were located in the primary structure of LA-ketose and LA-aldose conjugates, respectively. On the other hand, the antioxidant activities of protein-sugar conjugates and their peptic hydrolysates were investigated by 1,1-diphenyl-2-picrylhydrazyl radical scavenging method. The antioxidant activities of proteins/peptides glycated with rare sugars were significantly higher than those modified with the control sugars. The results indicated that the glycation degree and position were not markedly different between rare sugar and corresponding control sugar, but the antioxidant properties of protein and its hydrolysate were significantly enhanced by modifying with rare sugar.     

Mass spectrometric characterization of amino sugar aldononitrile acetate derivatives used for isotope enrichment assessment of microbial residues

Identifying the transformation of amino sugars in soils is essential in understanding microbial contribution to soil organic matter turnover and sequestration. Using a recently developed method, combining gas chromatograph/mass spectrometry (GC/MS) with laboratory incubation of substrates containing ¹³C or ¹⁵N isotopes, we were able to trace isotopic changes in amino sugar compounds. This allows us to quantitatively evaluate C or N enrichment in amino sugars during transformation in soils using the fragment (F) abundance ratio of m/z F + n to F (n is original skeleton atom number in each fragment). However, there is still lack of detail structural and substitutional information for each ion fragment. In order to improve the interpretation and increase our ability to study amino sugar turnover, we grew labeled amino sugars in lab-cultured organisms. We spectrometrically investigated the ion structures and original skeleton C number (mass shift n) in major ion fragments based on applying multiple representative isotope labels. Our results categorically confirm that previously made assumptions were correct regarding the substitutional number “n” of the glucosamine (He et al., 2006). Our study also added valuable structural information for aldononitrile acetate derivatized glucosamine and muramic acid upon electron impact ionization in MS.     

Fate of microbial residues in sandy soils of the South African Highveld as influenced by prolonged arable cropping

Long‐term cultivation of former grassland soils results in a significant decline of both living and dead microbial biomass. We evaluated the effect of duration of cropping on the preservation of fungal and bacterial residues in the coarse‐textured soils of the South African Highveld. Composite samples were taken from the top 20 cm of soils (Plinthustalfs) that have been cropped for periods varying from 0 to 98 years in each of three different agro‐ecosystems in the Free State Province. Amino sugars were determined as markers for the microbial residues in bulk soil and its particle‐size fractions. Long‐term cultivation reduced N in the soil by 55% and the contents of amino sugars by 60%. Loss rates of amino sugars followed bi‐exponential functions, suggesting that they comprised both labile and stable fractions. With increased duration of cropping the amino sugars attached to silt dissipated faster than those associated with the clay. This dissipation was in part because silt was preferentially lost through erosion, while clay particles (and their associated microbial residues) remained. Erosion was not solely responsible for the reduction in amino sugar concentrations, however. Bacterial amino sugars were lost in preference to fungal ones as a result of cultivation, and this effect was evident in both silt‐ and clay‐sized separates. This shift from fungal to bacterial residues was most pronounced within the first 20 years after converting the native grassland to arable cropland, but continued after 98 years of cultivation.     

Experimental assessment of habitat preference and dispersal ability of soil springtails

Beside biotic interactions, habitat preference and dispersal ability of species play a prominent role in the building of animal species assemblages. However, these traits are usually very poorly documented for soil organisms. A soil transfer experiment was designed to study habitat preference (including land-use and soil preference) and dispersal ability of soil springtail species living in a meadow and in an adjoining deciduous forest. The study was performed in the Morvan Regional Natural Park (Central France), using untreated or defaunated soil blocks, transferred to another land-use or replaced in their original land-use. Land-use preference was quantified in untreated and untransferred samples from meadow and forest. Dispersal ability was estimated from the time at which species colonized defaunated samples in their own habitat. Soil preference was estimated from the colonization rate of defaunated samples by comparing transferred and untransferred soil blocks. Results showed that in the community, 6% of species were land-use generalists, 30% were soil generalists and 36% recolonized defaunated soil blocks within a week. Land-use preference, soil preference and dispersal ability were largely independent components of species characteristics. Although our experiment dealt only with small-scale colonization, comparisons between species showed that the dispersal type based on anatomical features (legs, antenna, furcula, visual apparatus) does not allow predicting the dispersal ability of these species. Discrepancies between land-use preference and soil preference suggest that other habitat features must be relevant for Collembola, and that a trade-off exists between eco-physiological and biotic interactions (including food requirements).     

Enhancement of the foaming properties of protein dried in the presence of trehalose

Surface tension, foamability, and foam stability kinetics have been measured for the pure proteins bovine serum albumin (BSA) and beta-lactoglobulin, before and after aqueous solutions of the proteins had been subjected to different drying conditions, and also for whey protein concentrate (WPC). Pure proteins were air-dried, at 78 or 88 degrees C, in the presence and absence of sucrose or trehalose, at a mass ratio of 5:1 sugar/protein. WPC was spray-dried in the presence of various sugars: trehalose, sucrose, lactose, and lactitol. Spray-drying WPC without sugars resulted in a dramatic decrease in the foam stability, whereas drying in the presence of sugars gave better retention of the original foaming properties. Trehalose in particular resulted in almost complete retention of the foam stability observed for the nondried WPC. Pure beta-lactoglobulin showed similar behavior, but trehalose did not seem to afford the same protection to BSA.     

外源氮添加对土壤微生物残体积累动态的影响－基于Meta分析

微生物残体是土壤有机碳库的重要贡献者。为明确外源氮添加对土壤微生物残体积累动态的影响,本文收集整理了1980—2020年已发表的文献,共选取122组试验观测数据,利用整合分析方法（Meta-analysis）,以微生物残体标识物－氨基糖为目标组分,定量分析了不同种类和数量的外源氮添加对土壤中微生物来源细胞残体积累数量和组成比例的影响,并系统解析其主要影响因素。结果表明:外源氮添加（0 ~ 6000 kg hm?1）对微生物细胞残体的积累有显著的促进作用,并能引起土壤中真菌和细菌来源细胞残体相对比例发生明显变化。与不加氮对照相比,氮添加使土壤氨基糖总量增加27%,其中氨基葡萄糖、氨基半乳糖和胞壁酸含量分别增加22.5%、29.8%和19.0%。同时,不同种类外源氮素添加对氨基糖积累特征的影响也有所不同,表现为有机氮（如动物厩肥）比无机氮添加对氨基糖积累的促进作用更大。此外,氮添加对氨基糖的影响程度还与土壤自身的碳氮比、土地利用类型和自然降雨量等环境因子密切相关。其中是否添加碳源对微生物残体的响应有较大影响,表现为:无碳源添加会降低土壤氨基糖葡萄糖和胞壁酸对氮添加的响应,削弱了微生物残体对土壤有机质的贡献比例;而氮源同时配合碳源添加条件下,土壤氨基糖积累量显著高于单一氮源添加的处理,说明氮添加对微生物残体积累的影响存在着碳氮耦合效应。     

Hypoglycemic health benefits of D-psicose

Diabetes is an emerging health problem worldwide. The incidence of type 2 diabetes has dramatically increased and is expected to increase more rapidly in the future. Most patients with type 2 diabetes suffer from obesity and diabetes-related complications, including cardiovascular disease and hepatic steatosis. It has been proposed that simple sugar consumption is one of the major risk factors in the development of diabetes. Hence, the replacement of sugars with a low glycemic response would be an effective strategy to prevent type 2 diabetes. Accumulating evidence demonstrates that D-psicose, which has 70% the sweetness of sucrose and no calories, is a functional sugar exerting several health benefits preventing the development of diabetes. Although D-psicose presents in small amounts in natural products, a recent new technique using biocatalyst sources enables large-scale D-psicose production. More importantly, several clinical and animal studies demonstrated that D-psicose has hypoglycemic, hypolipidemic, and antioxidant activities, which make it an ideal candidate for preventing diabetes and related health concerns. This review will summarize the protective effects of D-psicose against type 2 diabetes and its complications, suggesting its potential benefits as a sucrose substitute.     

Microbial residues as indicators of soil restoration in South African secondary pastures

Prolonged intensive arable cropping of semiarid grassland soils in the South African Highveld resulted in a significant loss of C, N and associated living and dead microbial biomass. To regenerate their soils, farmers converted degraded arable sites back into secondary pastures. The objective of this study was to clarify the contribution of microorganisms to the sequestration of C and N in soil during this regeneration phase. Composite samples were taken from the topsoils of former arable land, namely Plinthustalfs, which had been converted to pastures 1-31 years ago. Amino sugars were determined as markers for microbial residues in the bulk soil and in selected particle-size fractions. The results showed that when C and N contents increased during the secondary pasture usage, the amino sugar concentration in the bulk soil (0-5 cm) recovered at similar magnitude and reached a new steady-state level after approximately 90 years, which corresponded only to 90% of the amino sugar level in the primary grassland. The amino sugar concentration in the clay-sized fraction recovered to a higher end level than in the bulk soil, and also at a faster annual rate. This confirms that especially the finer particles contained a high amount of amino sugars and were responsible, thus, for the restoration of microbially derived C and N. The incomplete recovery of amino sugars in bulk soil can only in parts be attributed to a slightly coarser texture of secondary grassland that had lost silt through wind erosion. The soils particularly had also lost the ability to restore microbial residues below 5 cm soil depth. Overall, the ratios of glucosamine to muramic acid also increased with increasing duration of pasture usage, suggesting that fungi dominated the microbial sequestration of C and N whereas the re-accumulation of bacterial cell wall residues was less pronounced. However, the glucosamine-to-muramic acid ratios finally even exceeded those of the primary grassland, indicating that there remained some irreversible changes of the soil microbial community by former intensive crop management.     

真空冷冻干燥果胶-纤维素-小分子糖气凝胶质构研究

为探究不同小分子糖对真空冷冻干燥(FD)果蔬质构的影响,并寻找蔗糖的替代品,本试验通过建立FD果蔬天然网络结构模拟体系——果胶-纤维素气凝胶体系,并在该多孔骨架结构上搭载11种小分子糖,考察了不同小分子糖对FD气凝胶的微观结构、质构、吸湿性和玻璃化转变温度(T_g)等品质的影响。结果表明,添加果糖、水苏糖、麦芽糖醇样品的硬度显著高于添加蔗糖样品,而添加海藻糖和低聚异麦芽糖样品的硬度显著低于添加蔗糖样品;所有样品中,仅果糖样品的脆度显著高于蔗糖样品;低聚果糖样品的外观、质构以及吸湿性品质均与蔗糖样品相近,且T_g较高。因此,在FD果蔬工业生产中,低聚果糖是极具发展前景的一种蔗糖取代糖。本研究结果证实了小分子糖是果胶-纤维素气凝胶形成硬度和脆度的物质基础,可为FD果蔬生产过程中小分子糖的选择提供理论依据。     

Sugars in soil and sweets for microorganisms: Review of origin,content, composition and fate

Sugars are the most abundant organic compounds in the biosphere because they are monomers of all polysaccharides. We summarize the results of the last 40 years on the sources, content, composition and fate of sugars in soil and discuss their main functions. We especially focus on sugar uptake, utilization and recycling by microorganisms as this is by far the dominating process of sugar transformation in soil compared to sorption, leaching or plant uptake. Moreover, sugars are the most important carbon (C) and energy source for soil microorganisms.Two databases have been created. The 1st database focused on the contents of cellulose, non-cellulose, hot-water and cold-water extractable sugars in soils (348 data, 32 studies). This enabled determining the primary (plant-derived) and secondary (microbially and soil organic matter (SOM) derived) sources of carbohydrates in soil based on the galactose + mannose/arabinose + xylose (GM/AX) ratio. The 2nd database focused on the fate of sugar C in soils (734 data pairs, 32 studies using ¹³C or ¹⁴C labeled sugars). ¹³C and ¹⁴C dynamics enabled calculating the: 1) initial rate of sugar mineralization, 2) mean residence time (MRT) of C of the applied sugars, and 3) MRT of sugar C incorporated into 3a) microbial biomass and 3b) SOM.The content of hexoses was 3–4 times higher than pentoses, because hexoses originate from plants and microorganisms. The GM/AX ratio of non-cellulose sugars revealed a lower contribution of hexoses in cropland and grassland (ratio 0.7–1) compare to forest (ratio 1.5) soils.¹³C and ¹⁴C studies showed very high initial rate of glucose mineralization (1.1% min⁻¹) and much higher rate of sugars uptake by microorganisms from the soil solution. Considering this rate along with the glucose input from plants and its content in soil solution, we estimate that only about 20% of all sugars in soil originate from the primary source – decomposition of plant litter and rhizodeposits. The remaining 80% originates from the secondary source – microorganisms and their residues. The estimated MRT of sugar C in microbial biomass was about 230 days, showing intense and efficient internal recycling within microorganisms. The assessed MRT of sugar C in SOM was about 360 days, reflecting the considerable accumulation of sugar C in microbial residues and its comparatively slow external recycling.The very rapid uptake of sugars by microorganisms and intensive recycling clearly demonstrate the importance of sugars for microbes in soil. We speculate that the most important functions of sugars in soil are to maintain and stimulate microbial activities in the rhizosphere and detritusphere leading to mobilization of nutrients by accelerated SOM decomposition – priming effects. We conclude that the actual contribution of sugar C (not only whole sugar molecules, which are usually determined) to SOM is much higher than the 10 ± 5% commonly measured based on their content.     

Effect of plant materials on microbial transformation of amino sugars in three soil microcosms

Amino sugars, being predominantly of microbial origin, can help elucidate the role of microbes in carbon and nitrogen cycling in soils. However, little is known about the microbial degradation and synthesis of soil amino sugars as affected by plant-derived organic materials. We conducted a 30-week microcosm study using three soils amended with soybean leaf or maize stalk to investigate changes in the amounts and patterns of amino sugars over time. The total soil amino sugar content initially increased during the incubation, but later decreased. Amino sugar content of soil amended with maize stalk peaked at an earlier time than it did for soybean leaf, suggesting nutrient quantity and substrate composition influence microbial transformation. Temporal dynamics of the proportion of total soil amino sugar to organic matter after plant material addition conformed to parabolic models (r > 0.8; p < 0.01), which tended to converge over time. The models predicted that the proportions would ultimately approach the initial values as determined before amendment. These findings suggest that soil organic matter has the ability to maintain a baseline steady-state level of amino sugars, and support the interpretation of soil amino sugar reservoir as two components: the Stable Pool (SP) and the Transition Pool (TP).     

“风味2号”甜瓜果实成熟过程中的品质变化

以60Coγ射线育出甜瓜新品种"风味2号"为材料,研究其果实发育和品质形成的动态变化。结果表明,从授粉后第5天开始果实快速膨大,第30天时鲜重达最大。从授粉后第29天开始,果肉可溶性糖含量迅速增加,其后保持稳定,至第34天显著降低。可滴定酸含量随果实的发育逐渐增加,糖酸比的高峰出现在授粉后第30-34天。气相色谱表明,"风味2号"果实中主要可溶性糖为果糖、葡萄糖和蔗糖,有机酸为苹果酸和柠檬酸,其中柠檬酸是主要有机酸。气相色谱-质谱联用分析显示:果实有35种挥发性物质,其中酯类占35.24%,酸类占19.21%,醇类为14.28%,醛类为11.71%。     

Heavy metal uptake by wheat seedlings grown in fly ash-amended soils

A bioassay technique was used to investigate heavy metals uptake by wheat seedlings grown in fly ash-amended soils. No negative effect of fly ash on the growth of wheat seedlings was found. The addition of the fly ash generally decreased the heavy metal concentration in the wheat seedlings. The total accumulation largely depended on the soil characteristics. The variation in the soil pH induced by the fly ash treatment could be considered the most important parameter that influenced heavy metals uptake. In the soil with a higher increase of pH (2 units) total accumulation of heavy metals decreased with increasing fly ash addition. In the other soils where the pH variation was lower (0.4 units), total accumulation of some heavy metals increased. These obtained data provide useful information which is required before the agronomic use of fly ash can be recommended in Italian soils.     

Improved characterization of the botanical origin of sugar by carbon-13 SNIF-NMR applied to ethanol

Until now, no analytical method, not even isotopic ones, had been able to differentiate between sugars coming from C4-metabolism plants (cane, maize, etc.) and some crassulacean acid metabolism plants (e.g., pineapple, agave) because in both cases the isotope distributions of the overall carbon-13/carbon-12 and site-specific deuterium/hydrogen isotope ratios are very similar. Following recent advances in the field of quantitative isotopic carbon-13 NMR measurements, a procedure for the analysis of the positional carbon-13/carbon-12 isotope ratios of ethanol derived from the sugars of pineapples and agave using the site-specific natural isotopic fractionation-nuclear magnetic resonance (SNIF-NMR) method is presented. It is shown that reproducible results can be obtained when appropriate analytical conditions are used. When applied to pineapple juice, this new method demonstrates a unique ability to detect cane and maize sugar, which are major potential adulterants, with a detection limit in the order of 15% of the total sugars, which provides an efficient mean of controlling the authenticity of juices made from this specific fruit. When applied to tequila products, this new method demonstrates a unique ability to unambiguously differentiate authentic 100% agave tequila, as well as misto tequila (made from at least 51% agave), from products made from a larger proportion of cane or maize sugar and therefore not complying with the legal definition of tequila.     

外源氮素和凋落物添加对温带森林土壤氨基糖转化特征的影响

【目的】温带森林土壤氨基糖的转化特征对外源氮素和凋落物加入的响应研究,对于温带森林土壤氮素管理和缓解氮沉降所带来的负面影响具有重要的意义。【方法】采用室内恒温恒湿模拟培养的方法,研究了外源氮素和凋落物添加条件下温带森林土壤有机层中3种微生物来源的氨基糖含量的变化特征,并利用真菌和细菌来源氨基糖的比值（氨基葡萄糖/胞壁酸）,分析了外源物质添加条件下真菌和细菌残留物对土壤氮素转化和积累的相对贡献。【结果】温带森林有机层土壤中不同微生物来源氨基糖对外源物质加入的响应不同。单施氮素以及氮素与凋落物同时添加均有利于细菌残留物胞壁酸的积累,但是单施氮素添加对真菌残留物氨基葡萄糖含量的积累没有影响,且氮素与凋落物同时添加不利于氨基葡萄糖含量的积累。氨基半乳糖对外源物质添加的响应较小。真菌残留物的稳定性高于细菌残留物,氮素与凋落同时加入时不利于土壤微生物残留物的稳定性。此外,土壤中真菌和细菌来源氨基糖的比值受到外源物质加入的影响,单施氮素以及氮素与凋落物添加降低了氨基葡萄糖/胞壁酸比值（分别降低28.3%和30.5%）,两种外源物质加入时细菌残留物对氮素转化的相对贡献大于真菌残留物。【结论】外源氮素和...