Stability and Antioxidant Activity of Food-Grade Phycocyanin Isolated from Spirulina platensis

Food-grade phycocyanin was obtained from Spirulina platensis cultured in seawater-based medium and purified by ammonium sulfate precipitation. The stability of phycocyanin under different conditions, including different pH, temperature, light, and edible stabilizing agents, was systematically investigated by spectroscopy methods. The optimum pH range for phycocyanin was found to be 5.0–6.0. Phycocyanin was kept stable at temperatures up to 45ºC over short time periods (i.e., no significant changes were observed in the relative concentration of phycocyanin, C_R). In contrast, incubation at a relatively high temperature resulted in a decrease in the C_R and half-life in a temperature-dependent manner. Constant exposure to light at 100 μmol m^–2 s^–1 for 36 h, decreased the C_R value of phycocyanin (pH5.0) to 78.4%. Sodium chloride was an effective stabilizing agent for phycocyanin, and its efficacy increased in a concentration-dependent manner for all concentration ranges assessed in this study. Moreover, phycocyanin exhibited concentration-dependent antioxidant activities in 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) and α,α-Diphenyl-β-pricrylhydrazyl assays. Taken together, our results suggest that the optimal conditions for preserving the stability of food-grade phycocyanin isolated from S. platensis are a pH of 5.0–6.0, low temperature, darkness, and the addition of edible stabilizing agents.     

The antioxidant properties of alcoholic extracts from Sambucus nigra L. (antioxidant properties of extracts)

The antioxidant properties of alcoholic extracts from the leaves, berries and flowers of Sambucus nigra L. are estimated by means of DPPH and β-carotene/linoleic acid methods, and considered in relation to the extraction temperature (in the range 20-200 °C) and to the level of flavonoids most representative for this plant. The extracts of S. nigra act as antioxidants neutralizing the activities of free radicals and inhibiting the co-oxidation reactions of linoleic acid and β-carotene. There is no direct correlation between the level of flavonoids in the extracts and their antioxidant activity. The data presented show that the extraction temperature strongly influences the antioxidant properties of the extracts, especially in the case of leaves.     

钝顶螺旋藻藻蓝蛋白的脉冲超声辅助提取技术

探讨钝顶螺旋藻藻蓝蛋白的脉冲超声辅助提取方法,并将脉冲超声辅助提取技术与传统提取方法——冻融法进行了对比。以钝顶螺旋藻为原料,采用脉冲超声辅助提取技术提取藻蓝蛋白,选定料液比、提取全程时间、循环泵转速、超声功率、超声发出时间和超声间歇时间作为参考因素,进行单因素和正交试验,优化得到的脉冲超声辅助提取最优工艺参数为:超声全程时间90min、超声功率1400W、超声发出时间6s、超声间歇时间9s、循环泵转速12r/s、提取温度20℃,当投料量为20g时,藻蓝蛋白的提取得率为13.45%,比冻融提取法高10.26%。这表明脉冲超声辅助提取法是一种高效分离钝顶螺旋藻藻蓝蛋白的方法。     

超声-微波协同提取螺旋藻中的叶绿素

研究了超声-微波协同提取螺旋藻中叶绿素的工艺。通过单因素试验确定了影响提取叶绿素的主要因素及最佳水平范围,通过正交试验确定的最佳提取工艺为提取温度55 ℃,超声提取时间300 s,料液比1∶14（g∶mL）。在此最佳条件下,螺旋藻中叶绿素的总提取率为1.141%。     

Antioxidant activity of Spirulina platensis extracts by supercritical carbon dioxide extraction

Supercritical CO₂ extraction of antioxidants from Spirulina platensis was optimized using response surface methodology. About 10.26 g/kg of extracts from S. platensis could be obtained under the optimum conditions of 48 °C at 20 MPa over a 4 h period. The antioxidant activity of the extracts prepared under the optimized condition, determined by linoleic acid peroxidation inhibition method, was lower compared with BHT and Trolox, but significantly higher than α-tocopherol in 300 min and became similar to α-tocopherol after that. The components of the extracts were further analyzed, and the results showed that the extracts contained 85.1 g/kg of flavonoids, 77.8 g/kg of β-carotene, 113.2 g/kg of vitamin A and 3.4 g/kg of α-tocopherol, which may contribute greatly to their high antioxidant activity. The main fatty acids in the extracts were palmitic acid (35.32%), linolenic acid (21.66%) and linoleic acid (20.58%).     

Influence of a Spirulina platensis biomass on the microflora of fermented ABT milks during storage (R1)

The objective of this research was to investigate the effect of a cyanobacterial (Spirulina platensis) biomass on the microflora of a probiotic fermented dairy product during storage at two temperatures. Spirulina-enriched and control (plain) fermented acidophilus-bifidus-thermophilus (ABT) milks were produced using a fast fermentation starter culture (ABT-4) as the source of Lactobacillus acidophilus (A), bifidobacteria (B), and Streptococcus thermophilus (T). Incubation took 6 h at 40 degrees C. As for the cyanobacterial product, the S. platensis biomass was added to the process milk during stirring at pH 4.5 to 4.6. Thereafter, the ABT-type fermented milks were cooled to 25 degrees C in ice water, filled into sterile, tightly capped centrifuge tubes, further cooled at 4 degrees C for 24 h, and then stored either at 15 degrees C for 18 d or at 4 degrees C for 42 d. Microbiological analyses and acidity measurements were performed at regular intervals. Our results showed that the counts of the starter organisms were satisfactory during the entire storage period at both temperatures applied in this research. The S. platensis biomass had a beneficial effect on the survival of ABT starter bacteria regardless of storage temperature. Postacidification was observed at 15 degrees C, whereas pH remained stable during refrigerated storage at 4 degrees C. The abundance of bioactive substances in S. platensis is of great importance from a nutritional point of view because thus the cyanobacterial biomass provides a new opportunity for the manufacture of functional dairy foods.     

酶法脱蛋白技术用于螺旋藻多糖提取工艺的研究

本文探讨了酶法脱蛋白技术在螺旋藻多糖提取工艺中的应用。研究结果表明，采用酶法脱蛋白可降低有机试剂的用量，缩短提取时间，效果优于Ｓｅｖａｇ脱蛋白法。     

Green processes based on the extraction with pressurized fluids to obtain potent antimicrobials from Haematococcus pluvialis microalgae

In the present work, the antimicrobial activity of different pressurized liquid extracts obtained from Haematococcus pluvialis microalga was tested against several microorganisms of importance for the food industry (Escherichia coli, Staphylococcus aureus, Candida albicans and Aspergillus niger). Extractions were performed with hexane and ethanol at four different temperatures (50, 100, 150 and 200 °C) for 20 min. The results showed that extracts obtained with both solvents (hexane and ethanol) from the green motile cells of the microalgae (green phase) presented a low antimicrobial activity against all the microorganisms tested. However, the antimicrobial activity of the extracts obtained from the red hematocysts without flagella (red phase) was totally different depending on the solvent used for the extraction. Hexane extracts showed an antimicrobial activity quite similar to that obtained with the green microalgae, while the antimicrobial activity of ethanol extracts was much higher. This fact seems to indicate that compounds related to antimicrobial activity of this microalga are found in higher quantities in the red phase of the microalgae and could be relatively polar compounds. Moreover, ethanol extracts from the red phase obtained at 100 °C presented the highest antimicrobial activity. In order to identify the compounds responsible for the antimicrobial activity, a GC-MS characterization of the extracts obtained with both hexane and ethanol at 100 °C, for Haematococcus pluvialis in the green and red phases was also performed. Therefore, the highest antimicrobial activity of the ethanol extract corresponding to red Haematococcus can be associated with the presence in this extract of short-chain fatty acids, which have been previously described to possess antimicrobial activity.     

Supercritical fluid extraction of antioxidant and antimicrobial compounds from Laurus nobilis L. Chemical and functional characterization

Extraction of laurel leaves by using supercritical carbon dioxide was carried out on a supercritical fluid (SF) pilot-scale plant. The extraction pressure and temperature were set to 250 bar and 60°C, respectively, using a 4% of ethanol as modifier. The employed apparatus, owing to a two-stage separation, allowed us to obtain two different fractions (F1 and F2), whose antioxidant and antimicrobial activities were investigated. Two different methods, β-carotene bleaching test and DPPH^• free radical–scavenging assay, were carried out to determine the antioxidant activity. Moreover, antimicrobial activity of laurel fractions was tested against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 10145, Escherichia coli ATCC 11775, Candida albicans ATCC 60193 and Aspergillus niger ATCC 16404. Minimum inhibitory concentration (MIC) and minimal bactericidal and fungicidal concentration (MBC) were obtained. Both fractions showed a similar antioxidant activity, although it was slightly higher for the fraction recovered in separator 2. However, antimicrobial activity against the microorganisms tested was only found when fraction 2 was used. Staphylococcus aureus was the most sensitive microorganism to this fraction, with maximal inhibition zones (25 mm) and the lowest MBC values (1.25 mg/ml), whereas the least susceptible was the fungi Aspergillus niger. In order to determine the compounds responsible for the antimicrobial activity, fraction 2 was analysed by GC–MS; results obtained showed that most of the compounds identified in the supercritical extract have been previously described to show antimicrobial activity; among them, the major compound found in the supercritical extract corresponded to a sesquiterpene lactone of the germacrolide type (6-epi-desacetyllaurenobiolide) previously described in laurel.     

钝顶螺旋藻藻蓝蛋白的提取工艺研究

为了研究钝顶螺旋藻藻蓝蛋白提取工艺的最佳条件,本文以钝顶螺旋藻干粉为原料,探讨高速匀浆法提取藻蓝蛋白过程中的各因素对其得率和产品纯度的影响。通过单因素与正交试验,确定最佳提取条件。结果表明:采用pH 7.0的PBS缓冲液为提取溶剂时,藻蓝蛋白得率最高为157.75 mg/g。经优化,当缓冲液溶剂添加量20倍,提取温度30℃,分3次匀浆提取共40 min时藻蓝蛋白得率达213.32 mg/g。比较乙醇沉淀法、酸沉淀法和盐沉淀法对藻蓝蛋白回收率的影响,结果表明采用50%的硫酸铵沉淀法藻蓝蛋白回收率达97.10%,藻蓝蛋白的纯度最高。采用高速匀浆法处理提取藻蓝蛋白,采用30%和50%分步盐析回收藻蓝蛋白,以本方法可获得纯度0.7以上的藻蓝蛋白239.70 mg/g干粉。经紫外可见光谱扫描显示,提取的藻蓝蛋白与藻蓝蛋白标品光谱特征一致。     

一株螺旋藻溶藻菌的分离、鉴定及溶藻特性初步研究

从黄化的螺旋藻体中分离出一株溶藻菌ES1,经形态、生理生化、16S rDNA序列分析鉴定为盐单胞菌属(Halomonas sp.)。该菌对螺旋藻有较好的溶解效果,能在24h使螺旋藻絮凝成团、黄化死亡,加入15%体积分数的菌液2d后螺旋藻去除率就可达到70.71%。实验表明,经0.22μm的微孔滤膜过滤,高温、低温灭菌处理的滤液,仍能强烈抑制螺旋藻生长,说明起溶藻作用的是ES1菌株的代谢产物,且该代谢产物在高温121℃和低温-80℃下稳定。ES1菌株生长速度快,对盐、碱有较强的耐受性,并能通过自身代谢产物调节pH至适合其生长的9.2左右,该菌的存在会使螺旋藻在短时间内大量死亡,对螺旋藻的大规模工业化养殖危害极大。     

Simultaneous determination of nine lignans using pressurized liquid extraction and HPLC-DAD in the fruits of Schisandra chinensis

The pressurized liquid extraction and HPLC-DAD was developed for extraction and determination of bioactive lignans in Schisandra chinensis. The efficient PLE conditions employed methanol as extraction solvent, 125 °C of extraction temperature, 5 min of static extraction time and only one cycle. A rapid HPLC-DAD method was described for simultaneous determination of nine lignans, including schisandrol A, gomisin J, schisandrol B, tigloylgomisin H, angeloylgomisin H, schisandrin A, γ-schisandrin, gomisin N and schisandrin C. The extraction efficiency of PLE was observed to be comparable with reflux and sonication. In addition, the contents of nine lignans in S. chinensis from different regions were analysed by PLE and HPLC-DAD method.     

Optimization and economic evaluation of pressurized liquid extraction of phenolic compounds from jabuticaba skins

The optimization of the extraction of anthocyanins and other phenolic compounds from jabuticaba skins, a promising Brazilian source of these compounds, was studied using pressurized liquid extraction (PLE). An optimization study was performed using ethanol as a solvent and with extraction pressure (5-10 MPa), temperature (313-393 K) and static extraction time (3-15 min) as independent variables. The optimum PLE conditions for all response variables were estimated; however, PLE conditions resulting in the highest recovery of anthocyanins (5 MPa, 553 K and 9 min of static extraction time) were chosen for comparison with a conventional low-pressure solvent extraction (LPSE). The attributes compared were yield, content of anthocyanins and phenolic compounds and economic feasibility. Similar extraction yields were obtained by LPSE and PLE under optimized conditions; however 2.15 and 1.66-fold more anthocyanins and total phenolic compounds, respectively, were extracted using PLE, while the cost of manufacturing (COM) obtained for the PLE extract was 40-fold lower.     

High performance liquid chromatographic analysis of phenolic compounds and their antioxidant activities in rice varieties

The analytical method for the determination of phenolic compounds in rice varieties was developed. The method consisted of extraction of phenolic compounds from rice before analysis by high performance liquid chromatography (HPLC). Reversed phase HPLC equipped with photodiode array detection was used and the separation condition was optimized. Under the optimum condition, twelve phenolic compounds were separated within 24 min. Pressurized liquid extraction (PLE) was used to extract free phenolic compounds from rice with the optimum extraction condition of 70% methanol and extraction time of 15 min. While, bound phenolic compounds were extracted using alkaline hydrolysis for 15 min. Six varieties of Thai rice including pigment and non-pigment rice in their brown and polished forms were investigated. All of 12 phenolic compounds were detected as free phenolic compounds in all samples. Ferulic acid was the most abundant free phenolic compounds in all samples, while ferulic acid and p-coumaric acid were found as bound phenolic compounds in some samples. The content of phenolic compounds, total flavonoid and antioxidant activity detected in pigment rice and brown form were higher than non-pigment rice and polished form.     

Protective effect of Spirulina platensis enriched in phenolic compounds against hepatotoxicity induced by CCl4

Phenolic compounds make up the major secondary metabolites with high pharmaceutical potential. Microalgae were reported to contain low amounts of phenolic compounds. The present study aimed to investigate the hepatoprotective potential of biomass of Spirulina platensis enriched in phenolic compounds. The protective effects of the biomass of S. platensis with low amounts of phenolics (SP1) and with high amounts of phenolics (SP2) against CCl₄-induced acute hepatotoxicity were evaluated in rats. The increased levels of ALT, AST and MDA along with decreased activities of SOD and CAT were significantly (p < 0.01) ameliorated by SP2. Histological examinations revealed that SP2 was more potent than SP1 in protecting the liver from toxic injury of CCl₄ and preserving the hepatocyte ultrastructure. The lesions including necrosis, lymphocyte infiltration, ballooning degeneration and hepatocyte injury as irregular lamellar organisation, dilations in endoplasmic reticulums and the presence of great number of cytoplasmic vacuolization were healed by SP2.