富硒乳酸菌筛选及其富硒工艺初探

首先对含有嗜酸乳杆菌(La),保加利亚乳杆菌(Lb),嗜热链球菌(St)的分离样品进行分离,纯化,筛选出纯菌种,然后分别进行富硒试验,通过抗性筛选和三角瓶发酵培养获得富硒能力优良的菌株和富硒条件。试验结果表明,嗜酸乳杆菌(La)富硒能力最强,其富硒条件初步确定为:选用番茄汁液体培养基,亚硒酸钠添加量为18μg/mL,pH6.6,37℃,培养24h,富硒能力为62.22%。     

富硒乳酸菌种的筛选

本实验从样品中分离,纯化,筛选出嗜酸乳杆菌(Lactobacillus acidophilus,简称 LA),保加利亚乳杆菌(Lactobacillus Bulgaria,简称 LB),嗜热链球菌(Streptococcus thermopiles,简称 ST)。通过富硒抗性筛选,确定了 LA 为耐硒菌种。通过对其发酵培养获得富硒能力优良的菌株和富硒条件,试验结果表明:选用番茄汁液体培养基,接种量 10%,加硒量 18μg/ml,pH 6.8,37℃培养 24h,有机硒含量可达 12.99μg/ml,转化率为 72.17%。     

富硒乳酸菌种的筛选

本实验从样品中分离，纯化，筛选出嗜酸乳杆菌(Lactobacillus acidophilus，简称LA)，保加利亚乳杆菌(Lactobacillus Bulgaria,简称LB)，嗜热链球菌(Streptococcus thermopiles，简称ST)。通过富硒抗性筛选，确定了LA为耐硒菌种。通过对其发酵培养获得富硒能力优良的菌株和富硒条件，试验结果表明：选用番茄汁液体培养基，接种量10％，加硒量18ug／ml，pH6．8，37℃培养24h，有机硒含量可达12．99μg／ml，转化率为72．17％。     

富硒乳酸菌的制备

课题以嗜酸乳杆菌(Lactobacillus acidophilus)、动物双歧杆菌(Bifidobacterium animals)、植物乳杆菌(Lactobacillus plantarum)、嗜热链球菌(Streptococcus thermopiles)作为供试菌株,进行富硒发酵试验,测定菌株的富硒能力及确定其适宜硒浓度。采用单因素试验和正交试验优化了益生菌的培养基组成。采用响应面法研究了富硒益生菌的发酵工艺,获得了富硒菌粉。结果显示:(1)在选购的4种乳酸菌中,嗜酸乳杆菌的富硒能力最强,且硒添加量为0～1 000 mg/kg时,嗜酸乳杆菌冻干粉的活菌数均能达到千亿级(即1×1012);优化的益生菌的培养基配方为蔗糖5%、蛋白胨与酵母膏的总添加量0.35%、蛋白胨-酵母膏比例3∶2、K2HPO4的总添加量0.1%;(2)优化嗜酸乳杆菌的最佳富硒工艺,并进行验证试验:菌种硒含量为2 902.81 mg/kg,加硒量为15.30 mg/kg,加硒时间为6.64 h。在此条件下,富硒益生菌产品得率为498.46 mg/kg,硒含量为13 039.62 mg/kg。     

富硒乳酸菌的分离、筛选、驯化及富硒研究

从酸奶中分离纯化出保加利亚杆菌(LactobacillusBulgaria,LB)和嗜热链球菌(StreptocociusThermopiles,ST),通过耐硒筛选,确定嗜热链球菌为耐硒菌种,以浓度梯度法对其驯化,从而得到富硒菌株,并进行富硒实验。初步确定富硒条件为:采用蕃茄酵母培养基,接种量10%,培养温度39℃,pH7,第6小时时加硒,硒浓度为15μg/mL,培养11h,富硒率为72.8%。     

水苏糖对山羊乳发酵的影响

以鲜羊乳为原料,保加利亚乳杆菌(LB)、嗜热链球菌(ST)和嗜酸乳杆菌(LA)为发酵剂,研究了添加水苏糖对普通酸羊乳(LB︰ST=2︰1)和嗜酸乳杆菌发酵乳(LA︰LB︰ST=1︰2︰1)发酵的影响。结果表明:普通酸羊乳的最佳水苏糖添加量为8%,在此添加量下,酸度最高为141.8°T,总菌数为1.60×109 CFU·mL~(-1),pH最低为3.68;嗜酸乳杆菌发酵羊乳的最佳水苏糖添加量为4%,发酵4.5 h后,发酵乳的酸度和pH分别为111.60°T和4.59,总菌数为1.52×109 CFU·mL~(-1),嗜酸乳杆菌活菌数为3.00×107 CFU·mL~(-1)。     

嗜热链球菌的分离筛选及与嗜酸乳杆菌共发酵制备酸奶的工艺研究

研究嗜热链球菌与嗜酸乳杆菌的生物学特性及共生作用。采用稀释涂布法和平板划线法,分离纯化嗜热链球菌,并鉴定和筛选优良发酵菌株。发酵条件为:加糖量7%,球杆菌混合比例l∶4,接种量4%(V/V),发酵温度40℃,效果最好。以嗜酸乳杆菌代替保加利亚乳杆菌与嗜热链球菌共发酵,通过优化的发酵工艺生产酸奶,可使酸奶的益生功能进一步增强。     

热休克法提高嗜酸乳杆菌的抗冻干胁迫作用

将乳酸菌在冷冻干燥前做热休克处理,可以提高其抗冻干胁迫能力。以菌体收集时期、热休克温度和热休克时间为热休克处理条件,通过单因素试验初步获得热休克对嗜酸乳杆菌抗冻干胁迫作用的影响,并以嗜酸乳杆菌冷冻干燥存活率为响应值,利用响应面分析获得热休克的最佳条件,即:嗜酸乳杆菌培养10.5 h,46℃热休克处理30 min。经此条件的热休克处理后,嗜酸乳杆菌冷冻干燥的存活率为56.77%,比未热休克处理的对照组存活率(37.68%)提高了50.66%。     

富硒短小芽孢杆菌D1-019的筛选与鉴定（英文）

将无机硒耐受性筛选和"红硒法"筛选相结合,经过4轮筛选,从前期分离的119株来源于鸭食的菌株中,筛选到1株富硒菌株D1-019。基于菌落形态观察、革兰氏染色、16SrDNA序列分析和系统发育树分析,D1-019菌株被鉴定为益生菌短小芽孢杆菌。采用正交试验设计方法,获得的最佳富硒条件为培养基初始pH5,30℃培养48h,培养6 h时加入质量浓度为20μg/mL的亚硒酸钠。在该富硒条件下,短小芽孢杆菌D1-019对培养基中亚硒酸钠的转化率为100%,菌体有机硒含量为(1 327±113)mg/kg,优于已报道富硒微生物。结果表明,短小芽孢杆菌D1-019有潜力开发成为一个可应用于食品领域的新富硒益生菌源。     

以麦麸为原料固态发酵开发多菌种微生态制剂的研究

试验以麦麸为主要原料,采用固态发酵技术,以纳豆芽孢杆菌和嗜酸乳杆菌为发酵菌种,以活茵数为指标,通过单因素和L9(34)正交试验确定了双菌混合发酵的最佳条件.结果表明:先接入纳豆芽孢杆菌,发酵3 d后接入嗜酸乳杆菌再共同培养3 d、培养基初始含水量80%、pH值7.0、纳豆芽孢杆菌和嗜酸乳杆菌接种比例为4:6、接种量10%、发酵温度37℃的发酵效果最好.在此条件下发酵后,纳豆芽孢杆茵数为9.8×109cfu/g,嗜酸乳杆菌数为7.1×109cfu/g.     

Selenium Content of Bison, Elk and Mule Deer

Selenium (Se) content of elk, mule deer, bison and beef skeletal muscle was measured and compared. Selenium content was determined by graphite furnace after wet nitric acid digestion. Game samples did not differ in Se content but contained more Se than beef (wet weight) (P<0.05). On dry weight basis, deer contained more Se than elk, bison or beef (P<0.05). Within samples from male elk and deer, and elk and bison of both genders, there were interactions between species and muscles (P<0.05). Type of muscle and gender did not influence Se content (P<0.05). Selenium toxicity from consuming game that foraged in high selenium environments is remote.     

Interactions of aqueous selenium (-II) and (IV) with metallic sulfide surfaces

The present study was initiated to determine the capacity of sulfide minerals (pyrite FeS2 and chalcopyrite CuFeS2) to delay the migration of inorganic selenium species in geological formations. Interactions between Se(IV) and Se(-II) and synthetic and natural sulfide minerals were investigated under anoxic conditions using the batch method. Significant sorption of selenium occurred under acidic conditions. Analysis of the solids after Se sorption using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) demonstrated the presence of reduced selenium species on the metallic sulfide surfaces, thus suggesting an oxido-reduction process coupled with sorption. Selenium reduction occurred concomitantly with the oxidation of pyritic sulfur, whereas metallic species (Fe, Cu) were not involved in the redox process. Formation of ferroselite (FeSe2) was postulated to take place on the synthetic solid while surface complexation or ionic exchange processes were more likely on the natural solids.     

饮用水中硒的形态分析——2,3-二氨基萘光度法测定硒(Ⅳ)、硒(Ⅵ)及总硒含量

应用２,３－二氨基萘（ＤＡＮ）对硒（Ⅳ）的选择性反应,生成的４,５－苯并苤硒脑经甲苯萃取,用分光光度法测定其吸光度,以研究饮用水中硒的存在形态。水样用ＨＮＯ３－ＨＣｌＯ４（５∶２）消化,将硒（Ⅱ）、硒（０）氧化为硒（Ⅵ）。用ＨＢｒ作还原剂,将硒（Ⅵ）还原为硒（Ⅳ）,然后进行测定,用差减法求得硒（Ⅳ）、硒（Ⅵ）及总硒的含量。     

Effects of dietary microalgae,other lipid sources,inorganic selenium and iodine on yolk n‐3 fatty acid composition,selenium content and quality of eggs in laying hens

BACKGROUND: This aim of this study was to investigate the effects of supplementing laying hen diets with different n‐3 fatty acid sources (linseed oil, fish oil and microalgae) on egg quality and fatty acid profile. The addition of inorganic selenium (Se) and iodine (I) and their effects on egg characteristics and Se concentration were also evaluated. RESULTS: A significantly lower egg weight was found in the control group and in groups fed a diet containing fish oil or a diet containing microalgae plus Se and I. Yolks from all supplemented diet groups exhibited a significant reduction in n‐6 fatty acid content compared with the control group. The docosahexaenoic acid (DHA) content of yolks was higher (P < 0.01) in all supplemented diet groups. Selenium supplementation increased the Se concentration (P < 0.001) in eggs. CONCLUSION: The results of this study provide evidence that an improvement in egg weight and in the DHA content of yolks can be achieved by feeding hens a microalgae‐rich diet, which avoids the unpleasant flavours associated with fish oil supplementation. Dietary inorganic Se, especially in combination with I, can enhance the concentration of Se in eggs. Copyright © 2009 Society of Chemical Industry     

Microscopically focused synchrotron X-ray investigation of selenium speciation in soils developing on reclaimed mine lands

Chemical speciation determines Se solubility and therefore its bioavailability and potential for transport in the environment. In this study we investigated the speciation of Se in soil developed on reclaimed mine sites in the U.S. Western Phosphate Resource Area (WPRA) using micro-X-ray absorption near-edge structure (micro-XANES) spectroscopy and micro-X-ray fluorescence (micro-XRF) mapping. Selenium was nonuniformly distributed in the soils and positively correlated with Fe, Mn, Cu, Zn, and Ni. Sixteen points of interest (POI) from three soil samples were analyzed with micro-XANES spectroscopy. The XANES data indicated that Se is present in the soils in at least three oxidation states, Se(-II, 0), Se(IV), and Se(VI). Selenides or elemental Se dominated 7 of the 16 POI. Selenate was the dominant species at only one of the POI. The remaining eight POI were composed of both Se(IV) and Se(VI), with minor Se(-II, 0) contributions. The results of this research suggest that the reduced Se species in the soil parent material are oxidizing to Se(VI), one of the more mobile species of Se in the environment. This information can be used to better predict and manage Se availability in soils.     

Chemical speciation and bioavailability of selenium in the rhizosphere of Symphyotrichum eatonii from reclaimed mine soils

Knowledge of rhizosphere influences on Se speciation and bioavailability is required to predict Se bioavailability to plants. In the present study, plant-availability of Se to aster (Symphyotrichum eatonii (A. Gray) G.L. Nesom) was compared in rhizosphere soils and nonrhizosphere (bulk) soils collected from a reclaimed mine site in southeastern Idaho, U.S. X-ray spectroscopy was used to characterize the oxidation state and elemental distribution of Se in aster roots, rhizosphere soils, and bulk soils. Percent extractable Se in aster rhizosphere soil was greater than extractable Se in corresponding bulk soils in all samples (n = 4, p = 0.042, 0.051, and 0.052 for three extractions). Selenium oxidation state mapping of 28 regions within the samples and X-ray absorption near edge structure (XANES) spectra from 26 points within the samples indicated that the rhizosphere and bulk soil Se species was predominantly reduced Se(-II,0), while in the aster roots, high concentrations of Se(VI) were present. Results show that within the rhizosphere, enhanced Se bioavailability is occurring via oxidation of reduced soil Se to more soluble Se(VI) species.     

Current knowledge in species-related bioavailability of selenium in food

Selenium is an essential trace element that has raised interest because of its antioxidant and anticancer properties. The beneficial or toxic effect of Se is not only dose-dependent, but also relates to the chemical form of the element and its bioavailability. In this review, recently published data is summarised concerning both Se speciation and Se relative bioavailability in various foodstuffs. In addition, Se bioavailability is discussed in relation to the species-dependent metabolism in humans. In this way, the understanding of the potential health impact of Se species in commonly consumed food is aimed to be improved. It is strongly suggested on the basis of a higher retention and a lower toxicity, that organic Se (especially SeMet, the major species in food) is more recommendable than inorganic Se in the frame of a balanced diet. Further research is however desirable concerning the characterisation of unidentified Se species and determination of their health effects.     

Selenium in cereals: Insight into species of the element from total amount

Selenium (Se) is a trace mineral micronutrient essential for human health. The diet is the main source of Se intake. Se-deficiency is associated with many diseases, and up to 1 billion people suffer from Se-deficiency worldwide. Cereals are considered a good choice for Se intake due to their daily consumption as staple foods. Much attention has been paid to the contents of Se in cereals and other foods. Se-enriched cereals are produced by biofortification. Notably, the gap between the nutritional and toxic levels of Se is fairly narrow. The chemical structures of Se compounds, rather than their total contents, contribute to the bioavailability, bioactivity, and toxicity of Se. Organic Se species show better bioavailability, higher nutritional value, and less toxicity than inorganic species. In this paper, we reviewed the total content of Se in cereals, Se speciation methods, and the biological effects of Se species on human health. Selenomethionine (SeMet) is generally the most prevalent and important Se species in cereal grains. In conclusion, Se species should be considered in addition to the total Se content when evaluating the nutritional and toxic values of foods such as cereals.     

Study of selenocompounds from selenium-enriched culture of edible sprouts

Selenium is recognised as an essential micronutrient for humans and animals. One of the main sources of selenocompounds in the human diet is vegetables. Therefore, this study deals with the Se species present in different edible sprouts grown in Se-enriched media. We grew alfalfa, lentil and soy in a hydroponic system amended with soluble salts, containing the same proportion of Se, in the form of Se(VI) and Se(IV). Total Se in the sprouts was determined by acidic digestion in a microwave system and by ICP/MS. Se speciation was carried out by enzymatic extraction (Protease XIV) and measured by LC-ICP/MS. The study shows that the Se content of plants depends on the content in the growth culture, and that part of the inorganic Se was biotransformed mainly into SeMet. These results contribute to our understanding of the uptake of inorganic Se and its biotransformation by edible plants.     

Selenium speciation in kerogen from two Chinese selenium deposits: environmental implications

Selenium is an essential trace element for humans, animals, and vegetation. Its occurrence in the environment is characterized by specific chemical and biochemical properties that control its elemental solubility, toxicity, and environmental behavior. The Laerma Se-Au deposit and Yutangba Se deposit are two important Se-bearing deposits found recently in China. In one of these areas (Yutangba), a serious environmental impact happened involving Se poisoning. Previous studies have shown that Se in both deposits is closely related to organic matter, especially kerogen fractions, but detailed relationships between Se and kerogen and Se chemical forms were not reported. In this study, the different speciation of Se is identified by transmission electron microscopy (TEM) and other geochemical techniques (infrared spectra (IS) and X-ray diffraction (XRD)) from kerogen samples extracted from ore rocks of both deposits. The occurrence of organically bound Se in the Laerma deposit and elemental Se nanograins in the Yutangba deposit is observed, indicating the diversity of formation mechanisms and possible chemical forms of Se in Se-rich rocks. The formation of elemental Se associated with organic matter is likely related to redox conditions, whereas organic species are related to the higher sulfur content of kerogen and possibly result from S-Se substitutions. This discovery provides new evidence with which to assess potential Se mobility during weathering of ore-bearing rocks. In an altered rock, the elemental Se in kerogen is more steadily mobilized and is potentially accumulated by vegetation, which may explain the sudden prevalence of Se poisoning in the Yutangba area. In contrast, organically bound Se seems more resistant to chemical alteration compared to other Se species so that its bioavailability may be very restricted.