Current knowledge on the extraction,purification, identification,and validation of bioactive peptides from seaweed

Seaweed (macroalgae) is considered as a sustainable bioresource rich in high-quality nutrients such as protein. Seaweed protein can be used as an alternative to other protein sources. Furthermore, these proteins are natural reservoirs of bioactive peptides (BAPs) associated with various health benefits such as antioxidant, antihypertensive, and antidiabetic activities. However, seaweed-derived BAPs remain underexploited due to challenges that arise during protein extraction from algal biomass. Coupled with this, limited proteomic information exists regarding certain seaweed species. This review highlights the current state of the art of seaweed protein extraction techniques, e.g., liquid, ultrasound, microwave, pulsed electric field, and high hydrostatic pressure assisted extraction. The review also focuses on the enzymatic hydrolysis of seaweed proteins and characterization of the resultant hydrolysates/peptides using electrophoretic and chromatographic techniques. This includes reference to methods employed for separation, fractionation, and purification of seaweed BAPs, as well as the methodologies used for identification, e.g., analysis by mass spectrometry. Furthermore, a bioinformatics or in silico approach to aid discovery of seaweed BAPs is discussed herein. Based on the information available to date, it is suggested that further research is required in this area for the development of seaweed BAPs for nutraceutical applications.     

烟用有机肥中氯离子含量测定方法的比较

为科学指导烟草栽培中有机肥的施用,以保证烟叶氯含量在适宜范围内,保障烟叶质量,研究比较了离子色谱法、连续流动分析法、硝酸银滴定法和佛尔哈德法测定烟用有机肥中氯离子含量.几种测定氯离子含量的方法比较结果为:离子色谱法和连续流动分析法测定烟用有机肥中氯离子含量的结果均较好,且方法不存在显著差异;硝酸银滴定法对低含量样品的检测偏差较大;佛尔哈德法不适宜用于测定烟用有机肥中氯离子含量.离子色谱法和连续流动分析法的平均回收率分别为102.4％、103.1％,方法检出限分别为0.05mg/L、0.30mg/L,对样品测定的平均相对标准偏差分别为2.41％和2.77％.     

石墨炉原子吸收光谱法测定海藻制品中的砷

应用石墨炉原子吸收光谱技术建立了在海藻制品中测定总砷和三价无机砷的方法,为开展海藻制品中无机砷的监测和食品安全风险评估提供准确的检测方法。采用湿法消解和微波消解为测定总砷的前处理方式,9m ol/L盐酸浸泡后乙酸丁酯萃取和纯水反萃取作为海藻制品中三价无机砷的提取方式,分别利用塞曼扣背景和氘灯扣背景的石墨炉原子吸收光谱法测定总砷和三价无机砷。塞曼扣背景测定砷的线性范围为3.0—60μg/L,定量限(LOQ)为2.9μg/L,精密度为3.6%,回收率为90%—102%;氘灯扣背景测定砷的线性范围为4.0—80μg/L,定量限(LOQ)为3.6μg/L,精密度为4.1%,回收率为88%—109%。本法对三价无机砷的提取方法简便实用、提取效率高。原子吸收光谱法的两种背景校正方式测定总砷及三价无机砷的结果准确可靠。为基层实验室开展食品中总砷以及三价无机砷的测定提供实用、可靠的分析方法。     

改进的QGA-ELM算法水稻叶面积指数反演模型

为了通过植被指数（VI）准确、可靠的获取不同施肥梯度、不同品种的水稻叶面积指数（LAI）,提出了一种基于改进的QGA-ELM算法应用于水稻LAI反演。首先通过8折交叉验证确定极限学习机(ELM)最佳的隐含层神经元个数与隐含层激活函数类型,再通过引入组合动态旋转角策略、单点混沌交叉操作、混沌变异操作、确定性选择策略、量子灾变操作对量子遗传算法（QGA）进行改进,最后使用改进后的QGA算法优化ELM神经网络输入层到隐含层的连接权值和隐含层的阈值。为了验证该模型普适性和有效性,依次建立多元线性回归、BP、ELM、QGA-ELM、改进的QGA-ELM算法5种模型,并在不同数据集上进行反演效果比较,结果表明：（1）对比QGA-ELM算法和改进的QGA-ELM算法进化过程,改进的算法能有效提升模型寻优能力,避免算法早熟,且能寻得更优结果。（2）对比五种算法在不同数据集上的反演效果,验证了NDVI,RVI与LAI之间主要为非线性关系,且ELM神经网络模型反演效果要优于BP神经网络模型和多元线性回归模型。（3）对比五种算法在不同数据集上的反演效果,改进的QGA-ELM算法绝大部分情况下拥有最高的反演精度和最低的误差,改进后的算法反演精度得到了明显提升,泛化性能也得到了增强。（4）改进的QGA-ELM算法在各种施肥梯度上均具有最高反演精度和最低误差,且精度较高,能为不同生长状况水稻LAI反演提供依据。（5）五种模型对庆和香LAI反演精度均要高于龙稻18,而改进的QGA-ELM算法在不同水稻品种上依然具有较高的反演精度,且在不同水稻品种上反演精度相差极小,远低于其他四种模型,能很好适应不同水稻品种LAI反演要求,极大提升模型的稳定性性,为不同水稻品种反演提供参考意义。     

Determination of Inorganic Ions in Fertilizer Industry Wastewater by Ion Chromatography

The aim of this work is development of methodology for analysis of inorganic cations (sodium, ammonium, potassium, magnesium and calcium) in fertilizer industry wastewater. Method development includes optimization of eluent flow rate and concentration of eluent competing ion in order to obtain optimal separation within reasonable analysis time. For that purpose artificial neural network retention model was developed and used in combination with normalized resolution product criteria function. Developed artificial neural network retention model shows good predictive ability R² ≥ 0.9983. The determined ion chromatographic parameters enable baseline separation of all components of interest. By performing validation procedure and number of statistical tests it is shown that developed ion chromatographic method has superior performance characteristic: linearity R² ≥ 0.9984, recovery = 99.81% − 99.44%, repeatability RSD ≤ 0.52%. That result proves that proposed method can be used for routine monitoring analysis in fertilizer industry.     

连续流动分析仪法测定水溶肥中氧化钾

采用连续流动分析仪法测定水溶肥中氧化钾含量,并与NY/T 1977-2010进行比较。结果表明,样品溶液中氧化钾在0～400mg/L范围内线性良好,相关系数r=0.9995,与四苯硼酸钾重量法结果比对结果接近,绝对偏差小于0.23%,准确度高,加标回收率在98.2%～100.6%之间,重现性良好,10次重复测定相对标准偏差为0.22%。     

Novel monohydrogenphosphate sensor based on vanadyl salophen

A novel PVC-based membrane sensor based on vanadyl salophen (VNSP) for determination of trace amounts of monohydrogenphosphate (MHP) ions is introduced. The electrode revealed Nernstian response towards monohydrogenphosphate over the wide concentration range from 1.0×10⁻¹ to 1.0×10⁻⁶ M at the pH of 8.2. The effect of solvent mediator, cationic additives and amount of ion-carrier on the behavior of the sensor was investigated. The sensor shows a short response time (<20 s) in the whole concentration ranges. The selectivity of the electrode is very high, and it can be used for detection of trace amounts of monohydrogenphosphate in the presence of large amounts of other anions. The detection limit of the electrode was 5.0×10⁻⁷ M (48 ng/ml) and it could be used for 14 weeks without any measurable changes in the slope. The potentiometric selectivity coefficients data revealed negligible interference from 16 common anions. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer samples and, as an indicator electrode, in potentiometric titration of HPO₄²⁻ ion with barium nitrate.     

Improved extraction of vegetable oils under high-intensity ultrasound and/or microwaves

Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) techniques have been employed as complementary techniques to extract oils from vegetable sources, viz, soybean germ and a cultivated marine microalga rich in docosahexaenoic acid (DHA). Ultrasound (US) devices developed by ourselves, working at several frequencies (19, 25, 40 and 300 kHz), were used for US-based protocols, while a multimode microwave (MW) oven (operating with both open and closed vessels) was used for MAE. Combined treatments were also studied, such as simultaneous double sonication (at 19 and 25 kHz) and simultaneous US/MW irradiation, achieved by inserting a non-metallic horn in a MW oven. Extraction times and yields were compared with those resulting from conventional procedures. With soybean germ the best yield was obtained with a ‘cavitating tube’ prototype (19 kHz, 80 W), featuring a thin titanium cylinder instead of a conventional horn. Double sonication, carried out by inserting an immersion horn (25 kHz) in the same tube, improved the yield only slightly but halved the extraction time. Almost comparable yields were achieved by closed-vessel MAE and simultaneous US/MW irradiation. Compared with conventional methods, extraction times were reduced by up to 10-fold and yields increased by 50–500%. In the case of marine microalgae, UAE worked best, as the disruption by US of the tough algal cell wall considerably improved the extraction yield from 4.8% in soxhlet to 25.9%. Our results indicate that US and MW, either alone or combined, can greatly improve the extraction of bioactive substances, achieving higher efficiency and shorter reaction times at low or moderate costs, with minimal added toxicity.     

Application of ultrasound-assisted acid leaching procedures for major and trace elements determination in edible seaweed by inductively coupled plasma-optical emission spectrometry

A new method using diluted reagents (nitric and hydrochloric acids and oxygen peroxide) and ultrasound energy to assist metals acid leaching with from edible seaweed was optimized. The method uses a first sonication at high temperature with hydrochloric acid as a previous stage to an ultrasound-assisted acid leaching with 7 ml of an acid solution containing nitric acid, hydrochloric acid and hydrogen peroxide at concentrations of 3.7, 3.0 and 3.0 M, respectively. Optimum conditions for the first sonication step were ultrasound energy at 17 kHz, sonication temperature at 65 °C, an acid volume of 2 ml, an hydrochloric acid concentration of 6.0 M and a sonication time of 10 min. It has been found that the first sonication stage at high temperature with hydrochloric acid is necessary to obtain quantitative recoveries for As, Ba, Fe and V. Otherwise quantitative recoveries were reached for the other elements investigated (Ca, K, Na, Mg, Cd, Cr, Cu, Mn, Ni, Pb and Zn). The repeatability of the ultrasound-assisted acid leaching method was around 10% for all elements. Adequate limit of detection and limit of quantification were reached by using inductively coupled plasma-optical emission spectrometry (ICP-OES) for measurements. The method resulted accurate after analysing several seaweed certified reference materials (IAEA-140/TM, NIES-03 and NIES-09). The method was finally applied to the multi-element determination in edible seaweed samples.     

Hazardous metal geochemistry of sedimentary phosphate rock used for fertilizer (Maz?dag, SE Anatolia, Turkey)

Composition of phosphate rocks mostly depend on their type and origin. Sedimentary rocks contain high concentration of heavy metals. Phosphate rocks are mainly used for the manufacturing of phosphate fertilizers. The contents of heavy metals Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn, as well as rare earth elements Ce, La, and Th were determined in sedimentary phosphate rock used for production of fertilizer in Turkey. The Kasrik-Semikan, Mazidag (Mardin, SE Anatolia, Turkey) high-grade phosphate rock used in this study is situated near the border with Syria and was deposited during the Turonian and Senonian (Cretaceous) ages. Total phosphorus (P) concentration in the rock is 18.5% on the average. Microwave acid digestion (MW-AD) followed by ?nductively Coupled Plasma-Optical Emission Spectrophotometry (ICP-OES) was carried out for the determination of all the elements of interest in phosphate rock. The results revealed that hazardous metal content of the phosphate rock was lower in Mazidag phosphate than that in samples imported from other countries and were within the safety limits.