柠檬酸对高岭石的溶解作用

采用间歇法(batch method)研究柠檬酸对高岭石溶解的影响。结果表明:低浓度(0.02mmolL-1)柠檬酸可促进高岭石中Ca2+、Mg2+、Na+少量的释放。当柠檬酸浓度分别为1.0mmolL-1和8mmolL-1时,Ca2+,Mg2+,K+,Na+,Si,Al3+阳离子的释放量也相应地增加。释放的Ca2+、Mg2+主要来自高岭石表面的吸附,而Na+、K+则来自高岭石的溶解。     

淹水条件下有机酸(糖)对土壤磷素固定的影响

以水田土壤剖面为对象,从磷素固定的角度研究了无定型铁等主要固磷基质在淹水加有机酸(糖)条件下的变化特征及其固磷能力变化特点。结果表明,剖面各层土壤淹水条件下添加有机酸(糖)培养后均可以与Langmiur方程很好拟合,淹水不添加有机酸(糖)与添加的处理相比,所有样品的最大固磷量均表现出降低的特点。淹水后土壤无定形硅含量与淹水前相比有所降低;无定形铁淹水前后变化不大但多数以含量增加为主,加酸(糖)处理中无定形铁含量表现出下降的趋势;络合态铁增加非常明显。无定性硅的变化与土壤固磷能力的变化相关性不显著,淹水前后无定形铁含量变化与最大吸磷量变化之间的相关性达到极显著水平,但淹水加酸(糖)后的最大吸磷量与淹水前相比多数样品有所降低;络合态铁氧化物主要表现为与磷素固定能力一定的负相关。     

绿色木霉 X-13株固态发酵产酶优化条件的研究

 对绿色木霉X-13株固态发酵产纤维素酶、半纤维素酶及果胶酶的优化条件进行了研究;通过综合评分的决策方法分析表明,X-13株的产酶优化条件是:稻草粉与麸皮的比例1.5∶1,料水比1∶1.5,氮源是2.0%～2.5%硫酸铵,培养基起始pH值6.0～6.5,250 mL三角瓶中装培养基15～20 g,培养时间60 h;以0.01 mol/L,pH 7.4 PBS于室温下浸提发酵培养基2 h,所得粗酶液活性最高。     

酸梅粉和柠檬酸对植酸酶改善生长猪钙、磷消化率的影响

本试验采用4×4拉丁方设计,旨在研究酸梅粉和柠檬酸对微生物植酸酶改善生长猪钙、磷消化率的影响。结果显示,在植酸酶的基础上添加1.5%酸梅粉使植酸磷、钙和磷的消化率分别提高17.52%(P<0.05)、21.78%(P<0.05)和27.24%(P<0.05),同时使钙和磷的沉积率也分别提高25.86%(P<0.05)和33.16%(P<0.05);添加1.5%柠檬酸使植酸磷、钙和磷的消化率分别继续提高了8.14%、16.51%和13.13%(P>0.05),同时使钙和磷的沉积率也分别提高了20.94%和12.61%(P>0.05)。以上结果表明,酸梅粉和微生物植酸酶在提高生长猪饲粮植酸磷消化率及钙磷利用率方面存在互作;柠檬酸仅有进一步提高植酸酶对植酸磷的消化和对钙磷的利用的趋势。     

低磷胁迫对大豆根系生长特性及分泌 H+和有机酸的影响

以不同基因型大豆nf37和冀黄13为材料,水培法研究大豆根系周围的酸化现象,并通过对大豆根干重、根冠比以及植株中磷含量的测定来探讨不同基因型大豆对枸溶性磷肥的利用效率。结果表明,低磷胁迫下,不同基因型大豆的根系均能主动向外界环境分泌H+;经HPLC分析得出,柠檬酸、草酸、酒石酸和苹果酸是主要分泌的有机酸;当向培养介质中添加枸溶性磷肥后,不同基因型大豆均可有效利用这一难溶性磷肥。无论是H+分泌量、有机酸分泌量还是对枸溶性磷肥的利用效率,耐低磷基因型大豆（nf37）都显著高于磷敏感基因型大豆（冀黄13）。表明,低磷胁迫均导致不同基因型大豆根系向介质中分泌H+和有机酸,同时还诱导大豆根系的加速生长,各项指标在耐低磷和磷敏感大豆基因型之间表现出显著差异,这可能是不同基因型大豆对枸溶性磷肥吸收、利用效率不同的原因。     

柠檬酸对珊瑚砂溶蚀过程及机理研究

有机酸在岩石矿物溶蚀风化及土壤形成的过程中具有较强的促进作用,了解柠檬酸对珊瑚砂的溶蚀过程对我国岛礁建设具有重要意义。本文通过不同浓度、不同pH柠檬酸溶液对珊瑚砂的溶蚀试验,研究柠檬酸对珊瑚砂的溶蚀过程,探讨其溶蚀机理。结果表明,在不同浓度柠檬酸溶液中,反应初期珊瑚砂中的Ca²⁺、Mg²⁺迅速溶出,随后大量的Ca²⁺与柠檬酸反应生成柠檬酸钙沉淀。平衡时溶液中Ca²⁺、Mg²⁺浓度随着柠檬酸浓度的增加而增加。在不同初始pH柠檬酸溶液中,当pH<7时,溶液中Ca²⁺、Mg²⁺的浓度随着初始pH的升高而降低,Ca²⁺、Mg²⁺主要由碳酸盐矿物与H+反应而溶出。当初始pH≥7时,Ca²⁺、Mg²⁺与柠檬酸生成络合物促进Ca²⁺、Mg²⁺的溶出,随着pH的升高,Ca²⁺、Mg^2...     

柠檬酸对红壤磷的持续活化效应及其活化机理的探讨

采用不同浓度的柠檬酸对红壤进行磷的持续活化试验。结果表明：随着浸提次数的增加，磷的活化量逐渐降低，但仍有少量的磷释放出来，且活化强度随着柠檬酸浓度的增大而加强。浸提前后土壤样品的无机磷分级结果表明：被柠檬酸活化的磷主要来源于土壤中Al-P、Fe-P及Ca—P中的磷，也有部分来自于有机形态的磷，同时柠檬酸能够促进土壤中闭蓄态磷（Oc—P）的形成与积累。Al-P、Fe-P及Oc—P中磷的活化量，受柠檬酸浓度的影响较大。柠檬酸浓度在5mmolL^-1和10mmolL^-1时，其被活化的量大小依次为Ca—P〉Al-P〉Fe-P；而柠檬酸浓度在100mmolL^-1时，其被活化的量为Fe—P〉Al-P〉Ca—P。     

Effect of native aggregation state of soluble wheat gluten on deamidation behavior in a carboxylic acid/heat water solution

To understand the role of native aggregation state (NAS) of soluble wheat gluten and fractions during deamidation in a carboxylic acid/heat water solution, changes in conformation and deamidation behavior as function of protein concentration from dilute to semi-concentrated regimes to control NAS were investigated by physicochemical properties, SDS-PAGE, molecular force change, intrinsic fluorescence emission spectroscopy (IFES) and FTIR. Our data show that, in this solution, the deamidated proteins displayed features characteristic of more scattered and flexible polymer structure in dilute concentration than concentrated ones. Degree of deamidation (DD), HD and Zeta potential exhibited strongly oppositely with the decreasing concentration. HWM-GS, ω-gliadins and LWM-GS degraded into smaller peptides with decreasing of NAS. FTIR and IFES displayed that improved molecular flexibility with decreasing of concentration as detected by the increasing content of β-turn and β-sheet, as well as the red-shift of wheat gluten and gliadins at the expense of α-helix. Hydrophobic and hydrogen bond increased gradually and were dominant in inter-molecule as function of increasing concentration. The above information demonstrated that NAS of soluble wheat gluten dominated changes of deamidation behavior and conformation in a carboxylic acid/heat water solution.     

圆叶决明牧草料栽培金顶侧耳对其产量和品质及重金属含量的影响

以圆叶决明豆科牧草为主原料栽培金顶侧耳，研究了该原料对金顶侧耳的产量、品质及重金属含量的影响。结果表明，其子实体产量比棉子壳料栽培的对照处理提高23．98％，而且可以明显改良菇类的品质。其子实体中硬脂酸、棕榈酸和亚油酸含量分别比对照提高40．0％、10．1％和3．1％，金顶侧耳子实体的化学评分(CS)、营养指数(NI)和生物价(BV)等品质评价指数分别比对照处理(棉子壳料)提高10．7％、7．1％和12．7％，而且子实体中Cd、Pb、Cr重金属含量分别比对照下降5倍、1倍和0．5倍。以圆叶决明牧草为主原料栽培的金顶侧耳子实体饱和脂肪酸(SFA)、单不饱和脂肪酸(MUSFA)、多不饱和脂肪酸(PUSFA)均高于棉子壳栽培料的对照处理。圆叶决明牧草料栽培的子实体SFA：MUSFA：PUSFA=1：0．17：4．44，而棉子壳料栽培的子实体SFA：MUSFA：PUSFA=1：0．22：4．76，显示了一定的差异。以圆叶决明牧草料栽培的金顶侧耳子实体K、P、Cu、Zn、Fe、Mn的含量分别为2．80％、1．22％、26．90％、136．23％、135．13％、10．25％，而棉子壳料的对照处理则相应为3．16％、1．03％、29．93％、67．74％、69．71％和67．70％，两者之间呈现明显的差异。     

Aluminum complexation suppresses citrate uptake by acid forest soil microorganisms

Organo-mineral interactions have been hypothesized to play a major role in biogeochemical cycling and pedogenesis in some forest soils. These processes are likely to be controlled to some extent by their persistence in soil, however, the factors regulating their bioavailability remain poorly understood. Therefore, we investigated the microbial utilization of ¹⁴C-labeled citrate in glass bead filled bioreactors containing a biofilm developed from an inoculum from an acid forest soil. The removal of Al-citrate in the bioreactors was negligible compared to the rate of citrate removal in the absence of Al. There was no evidence that in the short-term the microbial community adapted to increase the utilization of Al-citrate. In bioreactors filled with a Picea abies forest soil (Haplic Arenosol) the rates of citrate utilization were always slightly higher than that of Al-citrate. We conclude that complexation of citrate by metals such as Al may have a significant effect on their role in soil biogeochemical cycles.