Optimization of lipase-catalyzed regioselective acylation of pyridoxine (vitamin B6)

Response surface methodology was successfully applied to optimize lipase-catalyzed regioselective esterification of pyridoxine (PN). Effects of various reaction conditions, including reaction temperature, time, enzyme loading, substrate molar ratio, and water activity, were investigated. A central composite design was employed to search for the optimal conversion of PN. A quadratic polynomial regression model was used for analysis of the experimental data at a 95% level (p < 0.05). The analysis confirmed that the water activity was the most significant factor affecting the conversion of PN. It was also suggested that the conversion was strongly affected by independent variables of temperature, time, substrate molar ratio, and water activity as well as interaction terms of temperature and enzyme loading/substrate molar ratio/water activity, time and enzyme loading/substrate molar ratio, substrate molar ratio, and water activity. The coefficient of determination of the model was found to be 0.963. Three sets of optimum reaction conditions were established, and the verified experimental trials were performed for validating the optimum points. A scale-up experiment was also done under the first set of optimal conditions.     

Comparison of various extraction methods for policosanol from rice bran wax and establishment of chromatographic fingerprint of policosanol

A capillary gas chromatographic (GC) method has been developed for the separation and determination of policosanol components extracted from rice bran wax. A Varian CP-sil 8 CB column was employed, and an oven temperature was programmed. Gas chromatography-mass spectrometry (GC-MS) was used to identify the composition of policosanol. Quantitative analysis was carried out by means of hydrogen flame ionization detector (FID) with dinonyl phthalate (DNP) as internal standard. The results indicated that the extract obtained by dry saponification has the highest contents of octacosanol and triacontanol among extracts by all used extraction methods including dry saponification, saponification in alcohol, saponification in water (neutralized and non-neutralized), and transesterification. Meanwhile, the GC-MS fingerprint of policosanol extracted by dry saponification has been established. Euclidean distance similarity calculation showed remarkable consistency of compositions and contents among 12 batches of policosanol from a rice bran wax variety. This protocol provided a rapid and feasible method for quality control of policosanol products.     

Effect of the molecular mass and degree of substitution of oleoylchitosan on the structure, rheological properties, and formation of nanoparticles

Oleoylchitosans (O-chitosans), with different molecular masses and degrees of substitution (DS), were synthesized by reacting chitosan with oleoyl chloride. The FT-IR suggested the formation of an amide linkage between amino groups of chitosan and carboxyl groups of oleic acid. The viscosity of O-chitosan sharply increased with the increase of concentration, whereas that of unmodified chitosan rose only slightly. This increase was stronger as the increase of hydrophobicity (DS) and molecular mass of the polymer. The critical aggregation concentration (CAC) of O-chitosans with DS 5, 11, and 27% were 79.43, 31.6, 10 mg/L, respectively, and the CAC of samples with molecular masses of 20, 38, 300, and 1100 kDa were 50.1, 74.93, 125.9, and 630.9 mg/L, respectively. All of the O-chitosans could reduce surface tension slightly. Nanoparticles were prepared using an O/W emulsification method. Mean diameters of the polymeric amphiphilic nanoparticles of O-chitosans with DS 5 and 11% were around 327.4 and 275.3 nm, respectively.     

Synthesis and characterization of a molecularly imprinted silica gel sorbent for the on-line determination of trace Sudan I in Chilli powder through high-performance liquid chromatography

A highly selective imprinted polymer was synthesized by a surface molecular imprinting technique in combination with a sol-gel process. The imprinted polymer was evaluated by FT-IR and static and kinetic adsorption experiments. The results showed that the imprinted sorbent exhibited good recognition and selective ability, offered a faster kinetics for the adsorption and desorption of Sudan I than the non-imprinted sorbent, a saturated binding capacity (Qmax) that reached 33.47 mg g-1. The prepared sorbent was applied for the determination of trace Sudan I through on-line solid-phase coupled with high-performance liquid chromatography (SPE-HPLC). With a loading flow rate of 1.5 mL min-1 for sampling 50 mL, an enrichment factor of 1266 was achieved. The detection limit (S/N = 3) was 1.2 ng L-1, and the peak area precision (RSD) for five replicate detections of 0.01 microg L-1 Sudan I was 3.66%. The Sudan I in the chilli powder from the local market was determined at three levels (0.25, 0.5, and 1.0 ng g-1) with recoveries ranging from 80.31 to 94.02%.     

Determination of 10 carcinogenic polycyclic aromatic hydrocarbons in mainstream cigarette smoke

Polycyclic aromatic hydrocarbons (PAHs) are one class of chemical compounds that (1) are present at low to trace levels in unburned cigarette filler, and (2) are predominantly generated during combustion. According to a recent report of the International Agency for Research on Cancer, 10 carcinogenic PAHs together with 53 other known carcinogens are present in cigarette smoke. Accurate quantification of these chemicals helps assess public health risk to both smokers and nonsmokers exposed to second-hand smoke. We have developed and validated a specific and sensitive method for measuring these 10 carcinogenic PAHs in the particulate phase of mainstream tobacco smoke. Cigarette smoke particulate, produced using standard machine smoking protocols, was collected on glass fiber Cambridge filter pads. The particulate matter was solvent extracted, purified by solid-phase extraction, and analyzed by liquid chromatography/atmospheric pressure photoionization tandem mass spectrometry using isotopically labeled analogues as internal standards. Our method's limits of detection ranged from 11 to 166 pg and achieved sufficient reproducibility and accuracy to provide useful information on a range of cigarettes having dramatically different machine-smoked tar and nicotine deliveries. The identity of each PAH analyte was established from chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of the product/precursor ion pairs. This new method provides higher sensitivity, specificity, and throughput than did earlier methods. We found relatively consistent PAH levels among a selection of domestic full-flavor cigarettes. The PAH levels in smoke from highly ventilated light and ultralight cigarettes were low when smoked using ISO (International Organization for Standardization) conditions. However, if highly ventilated cigarettes were smoked under more intense conditions (e.g., larger or more frequent puffs, vents blocked), their PAH levels equaled or exceeded their full-flavor counterparts under ISO conditions.     

桂林毛村不同地质背景主要元素迁移特征及与植物蒸腾作用的相关性

对桂林毛村不同地质背景(石灰岩、白云岩和砂页岩)土壤中Ca、Mg、Cu、Fe、Mn、Zn等主要元素的迁移特征进行了研究,结果表明母岩的地球化学背景对岩溶土壤系统的元素迁移具有重要影响.同时,以不同地质背景生长的典型植物黄荆为例,研究了上述元素的迁聚与植物蒸腾作用的相关性.结果表明,植物蒸腾作用对土壤中Ca、Mg、Cu、Fe、Mn、Zn等主要元素迁聚的影响程度因不同地质背景以及不同元素而有明显差异.植物蒸腾作用对Mn、Cu等较难迁移元素的迁移具有一定促进作用.土壤中Cu、Fe、Mn、Zn等微量元素的迁聚对植物吸收系数的影响程度因不同地质背景而有显著差异.岩溶山区进行植被恢复时必须考虑不同地质背景的差异,因地制宜地选择合适的植物品种.     

不同土壤和氮钾肥配比对莴笋的营养效应研究

通过田间小区试验研究了不同N、K肥料配比对酸性和碱性土壤上两个莴笋品种(科兴 3 号和双尖莴笋)产量及品质的影响.结果表明,不同土壤上施用不同N、K配比肥料对双尖莴笋和科兴 3 号的产量影响不同.在酸性土壤上,对照(N15K10)是适宜两种莴笋高产的最佳N、K肥配比处理.在碱性土壤上种植双尖莴笋时,可以考虑在对照基础上适当地降低N肥用量.在碱性土壤上两种莴笋的产量均高于酸性土壤.减N和增K处理有利于降低莴笋的硝酸盐含量.在酸性土壤上莴笋中的硝酸盐含量高于碱性土壤.莴笋采收后期茎的硝酸盐含量高于叶片.不同施肥处理对两种土壤上科兴3号和双尖莴笋营养品质的作用不一致.在酸性土壤上增施K肥或提高N肥的用量对莴笋营养品质的改善更有效果.莴笋的Vc含量以叶片＞茎,且酸性土壤＞碱性土壤.除双尖莴笋在增K处理(N15K15、N20K15)中茎的可溶性糖含量表现为酸性土＜碱性土以外,其他处理莴笋茎叶中的可溶性糖均为酸性土＞碱性土.不同处理莴笋的氨基酸含量均表现为茎＞叶.     

不同因子对兰州百合组培小鳞茎诱导及膨大的影响研究

为了缩短兰州百合生长周期,提高百合品质,以兰州百合组培小鳞茎为材料,研究了大量元素、NAA、6-BA、培养基状态、蔗糖、2,4-D等单一因素对百合试管鳞茎形成和膨大的影响。结果表明,高浓度的大量元素有利于鳞茎的膨大,而不利于鳞茎的诱导;大量元素浓度为2MS时鳞茎平均直径最大,但新增鳞茎数下降到4.56个;NAA浓度为0.2 mg/L时新增鳞茎数最多且鳞茎平均直径最大;6-BA浓度为0.1 mg/L时最有利于鳞茎的形成和膨大,新增鳞茎数5.25个,鳞茎平均直径10.642 mm;固体培养基对鳞茎的形成效果明显,而半固体更有利于鳞茎的膨大;蔗糖浓度为90 g/L时新增鳞茎数最多,120 g/L时鳞茎平均直径最大;2,4-D浓度0.02 mg/L处理对鳞茎的形成和膨大效果更好。     

泰山引种竹子生长调查

“南竹北移”是将在南方生长良好的竹类品种移植到北方适宜地区,以满足北方地区常绿植物品种种植和生态工程建设的需要。“适宜”是“南竹北移”的必要条件。泰山处于暖温带气候区,温湿度适宜,海拔1 300 m以下土体湿润度大,一般土层较厚,为“南竹北移”提供了有利条件。文章分析了泰山竹类的种植历史、引种种类、生长现状等。     

加工番茄系统抗性诱导促生菌的筛选鉴定及其促生防病效果

【目的】 筛选具有诱导番茄系统抗性的促生菌并验证其对加工番茄早疫病、灰霉病的防效,为新疆加工番茄病害的生物防治提供理论依据和菌种资源。【方法】 采用稀释涂布法,分离番茄等作物的根部土壤细菌,以无菌生理盐水和稀释至10⁴倍数未接菌的NB培养基为空白对照,利用发芽实验初筛加工番茄促生菌;用菌株发酵液灌根处理加工番茄幼苗,以清水处理为空白对照,测量叶片中茉莉酸含量,复筛系统抗性诱导菌株,分别挑战接种番茄早疫病、灰霉病病原菌,统计疫情指数和诱抗效果。测定菌株16S rDNA序列,初步进行菌种鉴定。【结果】 共分离到147株细菌,筛选得到19株显著(P<0.05)促进加工番茄种子萌发、增加根长的促生菌,有4株促生菌显著(P<0.05)提高加工番茄叶片中茉莉酸含量,防病验证最终得到3株能同时有效防治加工番茄早疫病、灰霉病的菌株,诱抗防效在27.59%~39.44%。菌株FY10、FY12、FY93鉴定为Bacillus atrophaeus,Pseudomonas wadenswilerensis和Bacillus pumilus。【结论】 获得3株具有系统抗性诱导功能且有效防治加工番茄早疫病、灰霉病的促生菌。