Biodegradability of Poly (lactic acid), Preparation and Characterization of PLA/Gum Arabic Blends

In this study, the biodegradation of PLA films using microorganisms from Lake Bogoria (Kenya) were investigated. The biodegradation tests done using certain strains of thermophilic bacteria showed faster biodegradation rates and demonstrated temperature dependency. The biodegradation of the PLA films was studied using Gel Permeation Chromatography (GPC) and light microscopy. The biodegradation of PLA was demonstrated by decrease in molecular weight. The preparation and characterization of PLA/Gum Arabic blends were also investigated using DSC, TGA, TMA and NMR. In summary, the results obtained in this research show that PLA films undergo fast biodegradation using thermophiles isolated from Lake Bogoria. The PLA/GA blends studies show it is possible to prepare films of varying hydrophobic–hydrophilic properties for various applications.     

耐热乳杆菌的分离及在食物垃圾乳酸发酵中的应用

食物垃圾在我国城市生活垃圾中占有较大比重.发酵食物垃圾生产乳酸是实现其资源化的有效方法.从厌氧发酵的食物垃圾中分离到一株耐热乳酸菌TY50,根据形态、生理生化特征和16S rDNA序列,确定该菌株属于乳杆菌属的干酪乳杆菌组群(Lactobacillus casei group),其最高生长温度为52℃.TY50发酵食物垃圾生产乳酸的最佳同液比为1:12,最适温度为45 ℃.在pH 5.5～6.0条件下,发酵食物垃圾产生36.29 g/L的乳酸,乳酸体积产牢和转化率(乳峻/垃圾干重)分别达到1.01 g/(L·h)和0.44.     

改性粉煤灰在酸雾治理方面的研究

为去除化工生产等过程中产生的酸雾废气,首先用水作用法、微波法和传统湿法对粉煤灰进行改性试验,结果显示:传统湿法中的碱法效果最佳,改性后粉煤灰的BET比表面积是改性前的8.23倍.再用改性后的粉煤灰与廉价易得的天然矿物沸石和熟石灰作为活性组分,制得一种新型的复合吸附剂.常温常压下,动态吸附盐酸雾,实验结果表明:由改性粉煤灰制作的吸附剂G对盐酸雾的吸附性能比未经改性的吸附剂W有所提高,在文中所述条件下,饱和吸附量由改性前的331.4 mg/g提高到改性后的445.2 mg/g.     

低分子有机酸对土壤氟吸附的影响

用等温平衡吸附法研究了柠檬酸、草酸对砂姜黑土和潮土氟吸附的影响 ,提出了有机酸影响氟吸附的可能机理。实验结果表明 ,有机酸对土壤氟吸附有较大的影响 :(1)当有机酸处于低浓度时 ,土壤氟吸附量随浓度升高而增加 ;高浓度时 ,土壤氟吸附量随有机酸浓度升高而降低 ;(2 )在有机酸存在条件下 ,土壤氟的吸附量与平衡氟浓度间呈极显著的直线正相关或负相关     

Jasmonic acid treatment and mammalian herbivory differentially affect chemical defenses and growth of wild mustard (Brassica kaber)

Summary. Jasmonic acid (JA) is a wound-related hormone found in most plants that, when applied exogenously, can induce increases in levels of chemical defenses in patterns similar to those induced by mechanical damage or insect feeding. Relative to responses to insect and pathogen attack, chemical responses of herbaceous plants to mammalian herbivore attack have been little studied. In a field experiment, we compared the effects of JA treatment and naturally occurring mammalian herbivory on the expression of trypsin inhibitors, glucosinolates, peroxidase activity and growth of wild mustard (Brassica kaber). Exogenous JA significantly increased trypsin inhibitor activity and glucosinolate concentration, and moderately increased peroxidase activity in the eighth true leaves of five-week-old plants, relative to untreated controls. In contrast, levels of these chemical defenses in the eighth true leaves or in regrowth foliage of plants that had ∼80% of their leaf area removed by groundhogs (Marmota monax) did not differ from that in undamaged and untreated controls. Although exogenous JA significantly elevated levels of chemical defenses, it did not affect height of plants through the season and only slightly reduced time to first flower. Groundhog herbivory significantly reduced height and delayed or abolished flowering, but these effects were not substantial unless coupled with apical meristem removal. We hypothesize that the lack of effect of groundhog herbivory on chemical defenses may be due in part to the speed and pattern of leaf area removal by groundhogs, or physiological constraints caused by leaf area loss. Despite having no effect on chemical defense production, leaf area loss by groundhogs was more costly to growth and fitness than the effects of JA application in this study, but only substantially so if coupled with apical meristem removal. We suggest that in general, costs of defense production in plants are likely to be minimal when compared to the risk of losing large amounts of leaf area or primary meristematic tissue. Thus, if they are effective at deterring herbivory, the benefits of inducible defense production likely outweigh the costs in most cases. Received 20 December 2000; accepted 3 May 2001     

Benzoic acid, a stimulant of odorant receptors of Bombyx mori, is rapidly metabolized to N-benzoylserine on the antennae

Summary. Benzoic acid is a known stimulant of olfactory receptor cells in trichoid sensilla on the antennae of adult females of Bombyx mori. Exposure of freshly excised antennae, from B. mori females and males, to vapours of [¹⁴C]-benzoic acid revealed that the adsorbed acid is rapidly metabolized (15% conversion in 10 s), suggesting the presence of a highly active enzymatic system. The major product could be identified as N-benzoylserine by use of [²H₅]-benzoic acid, and mass spectrometry linked to a gas chromatograph (GC-MS) or a liquid chromatograph (LC-MS), for analysis of the metabolites. The conjugation of benzoic acid with an amino acid apparently represents a novel mode for the rapid deactivation of odorant molecules. Received 26 March 2001.     

蒽醌染料中间体溴氨酸降解酶的特性

从污染地分离筛选出的菌株BX26对蒽醌染料中间体溴氨酸有显著的降解脱色作用,降解过程受降解酶的控制,试验结果表明,降解酶为溴氨酸诱导的胞外酶,该酶在温度高于50℃处理后失活,盐度对该酶失活有影响,盐度高于1%会显著降低该酶活力,酶对溴氨酸的催化脱色要有氧参加,氮气气氛中酶活受抑制。     

硫酸含汞问题的追踪研究

以辽宁省最大的硫酸生产企业（辽西某锌厂）为研究对象,剖析了硫酸含汞问题的来源,论述了该厂原料、中间产品、最终产品、车间内外环境汞的污染状况。并论述了使用该厂硫酸的十大企业的中间产品、最终产品的含汞状况,给出了厂内外环境受汞污染的测定结果,研究表明含汞硫酸污染问题是急待解决的重要问题。     

间歇-阶段性酸雨入侵对填埋稳定化飞灰中重金属浸出行为影响

以间歇-分阶段进水方式进行了模拟酸雨柱式动态淋溶实验.结果表明,间歇-阶段性酸雨入侵会影响填埋飞灰中Pb、Zn、Cu、Cr和Ni的浸出行为;尤其间歇停滞期后的初期酸雨入侵会增加多数重金属的再浸出水平,且该部分重金属的释放主要源于前阶段酸雨侵蚀过程中所形成的非稳定性(弱酸态)重金属.各酸雨侵蚀阶段,部分重金属(如Pb-Zn)的浸出行为具有相关性,这与各重金属在飞灰基质内的赋存形态、矿物相稳定性及酸性侵蚀程度等有关.各阶段酸雨入侵会相继溶出飞灰中的可溶性(NaCl、KCl等)、难溶性氯盐(CaClOH)以及微溶性钙盐(CaSO₄),并增加CaCO₃和Ca-Al-Si-O等矿物的峰强.各阶段酸雨入侵会使初始飞灰表面的团簇状结构逐渐被酸性(H⁺)侵蚀作用破坏,并暴露出大量棒状或条形状CaCO₃晶体,且随着酸雨入侵次数的增加,CaCO₃也将逐渐被侵蚀破坏.本研究为非连续酸性降雨条件下填埋稳定化飞灰的重金属浸出行为评价及风险管控提供了科学依据.     

pH值调控柠檬酸污泥厌氧发酵产酸及碳源潜力研究

以柠檬酸废水厌氧颗粒污泥为接种物,在不同pH值调控条件下开展柠檬酸生产废水剩余活性污泥厌氧发酵产酸研究.通过对发酵液挥发性脂肪酸(VFAs)、有机质、氮磷和污泥脱水性能的分析,探讨了柠檬酸污泥厌氧产酸机制.结果表明,pH≥10的碱性条件更有利于有机质的溶出从而促进VFAs的产生.三维荧光光谱分析发现在恒定pH值下腐殖酸(HA)和富里酸(FA)会大量溶出降低VFAs的产量.初始pH=10是柠檬酸污泥厌氧产酸的最佳p H值,发酵4d的VFAs浓度最高达(6681.47±126.82)mgCOD/L,是文献报道中市政污泥产酸量的近2倍,其中乙酸占比49.8%,发酵后产酸功能菌Chloroflexi、Bacteroidota的相对丰度分别由初始的9.52%、10.87%增至16.84%、14.39%,污泥归一化毛细吸水时间(nCST)为(11.34±0.27)s·L/g,脱水性能良好,发酵液TP浓度为(20.45±0.33) mg/L.研究表明,利用柠檬酸剩余活性污泥碱性厌氧发酵产酸作为污水处理过程中的外加碳源具有较大潜力.