高油脂产率微藻的筛选及发酵条件的优化

本研究旨在从自然水域分离、筛选出高油脂产率的微藻藻株,对其生产油脂的发酵条件进行优化,以期为用微藻制备生物柴油的工业化生产打下基础.从不同淡水环境中分离纯化了17株微藻,根据形态特征对这些微藻进行了初步鉴定.比较了其中11株微藻的生物量、油脂含量及油脂产率.从中选取生物量和油脂含量都较高的椭圆栅藻(Scenedesmus ovalternus)、雷氏衣藻(Chlamydomonas reinhardii)和蛋白核小球藻(Chlorella pyrenoidosa)3株微藻,研究了光照、温度、pH、碳源、氮源及不同水平碳氮源组合对其比生长速率和油脂产率的影响,结果表明,添加葡萄糖作为碳源时3株微藻生长较快,油脂产率较高;其最适发酵温度为28(2;椭圆栅藻和蛋白核小球藻最适pH为7,而雷氏衣藻最适pH为9;葡萄糖和尿素分别为这3种微藻的最适碳源和氮源.从油脂产率方面考虑,椭圆栅藻的最佳碳、氮源组合为:30g/L葡萄糖和2.1 g/L尿素;蛋白核小球藻的最佳碳、氮源组合为:40 g/L葡萄糖和2.1g/L尿素;雷氏衣藻则为:30/L葡萄糖和1.2g/L尿素.雷氏衣藻和蛋白核小球藻的5 L发酵试验表明,与摇瓶培养相比,发酵培养时间由7 d缩短为5 d,OD540nm分别可达61.2和59.9,而且2株微藻生物量干重分别由11.2 g/L和8.8 g/L提高到26.58 g/L和20.19 g/L,油脂含量分别由20.3%和17.2%提高到23.2%和20.1%,油脂产率分别由0.3248 g/L/d和0.2162 g/L/a提高到1.2333 g/L/d和0.8112 g/L/a.本研究结果表明,从天然水域分离、筛选得到的两株微藻雷氏衣藻(Y7)、蛋白核小球藻(Y9)经过发酵条件优化控制油脂产率分别可达1.2333 g/L/a和0.8112 g/L/a,有望应用于利用微藻制备生物柴油的工业化生产.     

高密度高含油率微藻培养研究进展

微藻以其生长周期短、不占用农业耕地而被作为第三代生物柴油的首选原料,然而微藻培养密度偏低含油率不高是制约微藻生物柴油规模生产的主要因素。结合微藻培养的营养方式和培养系统,讨论了近年来提高微藻培养密度及油脂（主要为甘油三酯）含量的各种研究方法及成果,分析了微藻高产油率的培养模式,并就培养成本问题做了进一步探讨。最后总结了微藻生物柴油的发展方向,即在合适的培养系统下以太阳光为能源,充分利用废气、废液甚至废固培养微藻,提高藻油的生产率,从而降低生物柴油的生产成本,进而实现工业化生产。     

动物油脂热压联合提取装置设计与试验

提高病死畜禽胴体中的油脂提取率是实现病死畜禽进一步资源化的关键,为此该研究设计了一种动物油脂热压联合提取装置。首先基于静力学和热传递分析,结合动物油料特性,对关键部件压力机构和油脂提取机构进行了设计,并对加热、加压和可编程控制系统分别进行了关键参数设计和设备选型,最后选取板油进行了装置性能试验,并对提取的油脂进行了黏度测试。结果表明：在70～150℃范围内,单独温度和热压联合两种油脂提取方法的最佳温度均为130℃,在此温度下油脂提取率最高分别可达到59.15%和81.35%。相同温度下,热压联合油脂提取率较单独温度作用最高可提升31.21个百分点。减小油料规格对单独温度作用可明显提高油脂提取率,而对热压联合油脂提取率无明显影响。在高于130℃试验温度下进行热压联合油脂提取,能够达到油脂完全提取效果,所提取油脂在70～150℃温度范围内测得黏度为0.004～0.091 Pa·s,符合工业用润滑油黏度标准。     

排碱渠水中产油微藻分离鉴定及培养产油

针对新疆地区经排碱渠排放的大量盐碱水,目前仍缺乏资源化利用,不但造成水资源浪费,也对周边土壤生态环境带来严重威胁。该研究从排碱渠水中分离得到一株产油微藻WY205,经鉴定为小球藻（Chlorella sp.）,在此基础上,以排碱渠水为培养基质,考察了补充有机碳源对该藻生长及油脂积累的影响,以及微藻的盐耐受性、在半连续培养模式下该藻的生长与产油稳定性。结果表明,补充适量有机碳源可有效提高微藻生长速率和油脂产量,微藻油脂积累过程属于生长偶联型,Logistic方程和Gaden生长相关模型方程可较好地描述该藻的生长和油脂生成动力学过程,添加2.5 g/L葡萄糖可获得最大生物量（3.03 g/L）和最高油脂产量（1.26 g/L）,分别为不加糖处理的1.35、2.21倍。培养基中Na+添加至5 g/L时（折合NaCl 12.72 g/L）,微藻油脂产量比排碱渠水原液培养处理（Na+浓度2.64 g/L）提高了21.69%;继续增加Na+浓度至10 g/L（折合NaCl 25.43 g/L）,微藻油脂产量相比排碱渠水原液处理依然提高了10.84%,说明该藻具有较高的盐耐受性。经60 d共6个周期的半连续培养,该藻生物量和油脂产量无显著（P>0.05）变化,表现出良好的适应性和稳定性。该研究表明利用排碱渠水培养产油微藻可行,可为排碱渠水的资源化利用提供技术参考。     

水媒法提取食用油技术研究进展

该文提出了水媒法提油技术的概念。水媒法提油技术是指以水为主要媒介的提油技术(水媒法),可辅以或不辅以与水互溶的可食用物质(例如乙醇)、食品级酶、超声波、微波等处理以破坏油料细胞壁和/或破乳的食用油提取方法。水媒法的提油过程主要分为分成破碎、提取、破乳和分离四个阶段。水媒法发展至今60余年,已全面发展了水代法、水酶法和乙醇水提法等多种制油技术。目前水媒法的产业化还存在一些问题,如油料的预处理、酶的种类与成本等。但是,水媒法绿色健康、符合可持续发展要求,随着工艺设备、分离技术等的发展,该技术将更加完善,成为未来未来取代传统工艺的新主流。该文将水媒法研究领域的成果进行归纳总结并为其未来发展提供理论参考。     

溶剂萃取对螺旋藻水热液化生物原油储存稳定性的影响

为了研究生物原油所含不同组分对其储存稳定性的影响,该研究提出利用溶剂分步萃取法分离生物原油。采用螺旋藻为原料进行水热液化,利用极性不同的四氢呋喃、乙酸乙酯、丙酮和正己烷为萃取溶剂分离生物原油,以黏度和热值作为稳定性评价指标,利用热重分析仪、气相色谱质谱联用仪和傅立叶红外光谱仪分析生物原油的老化机理。结果表明：乙酸乙酯萃取得到的生物原油的黏度最低（316 mPa•s）,流动性最好,且在储存过程中黏度变化率最小（78.6%）,稳定性最好;利用溶剂可以分离生物原油中的重、轻组分和极性、非极性组分,生物原油的老化与极性大分子之间发生的酯化反应、聚合反应密切相关,而小分子非极性化合物的存在可显著降低生物原油的黏度,提高其流动性和稳定性;经储存后生物原油的热值降低了0.4%～6.2%,生物原油的极性组分、重组分和氮元素含量越多,黏度和热值的变化率越大。该研究可为生物质水热液化产物的定向调控及生物原油储存稳定性的提高提供参考。     

适宜提取方法提高美藤果油提取率及油品质

为了提高美藤果油的提取率以及油的品质,该文以美藤果为原料,比较了水酶法、超临界CO2萃取法、超声波辅助有机溶剂萃取法和低温冷榨法这4种不同的提取方法对美藤果油提取率和油品质的影响;并采用气相色谱-质谱联用法（gas chromatograph-mass spectrometer-computer, GC-MS）和高效液相色谱法（high performance liquid chromatography, HPLC）测定美藤果油的营养组成,以及以1,1-二苯基-2-三硝基苯肼（1,1-Diphenyl-2-picrylhydrazyl radical 2,2-Diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl,DPPH?自由基）清除率为指标比较了美藤果油与其他植物油的体外抗氧化活性。结果表明：4种提取方法中,水酶法和超声波辅助有机溶剂提取法油脂提取率较高,分别为95.1%和92.7%,其次为超临界萃取法,为86.44%。但超临界CO2萃取法提取出的油脂综合理化指标优于其他３种提取方法,其中水酶法提取出的油不溶性杂质、酸价、过氧化值和黄色值都低于超声波辅助有机溶剂萃取法和低温冷榨法,但感官品质最差。综合考虑得出：超临界萃取法为美藤果油较佳的提取方法。此方法提取的美藤果油中富含不饱和脂肪酸和生育酚、多酚等活性成分,不饱和脂肪酸质量分数高达92.37%,总生育酚和总多酚质量分数分别为59.2 mg/(100 g)、10.2 mg/(100 g),但不含有维生素A;美藤果油对DPPH·自由基的半数抑制率IC50为1.148 mg/mL,明显低于橄榄油、茶油、亚麻籽油和紫苏油（P<0.01）,说明美藤果油体外抗氧化能力较强。研究结果可为美藤果油进一步开发提供参考。     

Multiresidue method for the analysis of pesticide residues in fruits and vegetables by accelerated solvent extraction and capillary gas chromatography

An analytical procedure using accelerated solvent extraction and capillary gas chromatography with electron capture and flame photometric detections was developed to simultaneously determine residues of different pesticides in fruits and vegetables. Single laboratory validation of the method was carried out for 28 compounds selected from eight pesticide classes, in blank and fortified samples of fresh pear, cantaloupe, white potato, and cabbage. The method had to meet specific established validation criteria for regulatory purposes applicable to our laboratory. At each of the two fortification levels studied, 24 of the 28 pesticides gave recoveries of more than 70% with a coefficient of variation of less than 10%. With respect to existing procedures, the method showed acceptable limits of detection (from 0.0019 to 0.14 microg/g depending on the pesticide and matrix) while minimizing environmental concerns, time, and labor.     

Optimum methanol concentration and solvent/peanut ratio for extraction of aflatoxin from raw peanuts by modified AOAC method II

The amount of aflatoxin extracted from raw peanuts by using the water-slurry modification of AOAC Method II was determined for 49 different combinations of methanol concentrations and solvent/peanut ratio. Results indicate that the amount of aflatoxins B1 and B2 extracted from raw peanuts is a function of both methanol concentration and solvent/peanut ratio, and a cubic equation was developed, using regression techniques, to describe the combined effects. From the functional relationship, the predicted methanol concentration and solvent/peanut ratio that extracts the most aflatoxin B1 was computed to be 60.0% and 10.8 mL solvent/g peanuts, respectively. This combination extracted 12.1% more aflatoxin than did AOAC Method II.     

Impact of DNA extraction method on bacterial community composition measured by denaturing gradient gel electrophoresis

The impact of DNA extraction protocol on soil DNA yield and bacterial community composition was evaluated. Three different procedures to physically disrupt cells were compared: sonication, grinding-freezing-thawing, and bead beating. The three protocols were applied to three different topsoils. For all soils, we found that each DNA extraction method resulted in unique community patterns as measured by denaturing gradient gel electrophoresis. This indicates the importance of the DNA extraction protocol on data for evaluating soil bacterial diversity. Consistently, the bead-beating procedure gave rise to the highest number of DNA bands, indicating the highest number of bacterial species. Supplementing the bead-beating procedure with additional cell-rupture steps generally did not change the bacterial community profile. The same consistency was not observed when evaluating the efficiency of the different methods on soil DNA yield. This parameter depended on soil type. The DNA size was of highest molecular weight with the sonication and grinding-freezing-thawing procedures (approx. 20 kb). In contrast, the inclusion of bead beating resulted in more sheared DNA (approx. 6-20 kb), and the longer the bead-beating time, the higher the fraction of low-molecular weight DNA. Clearly, the choice of DNA extraction protocol depends on soil type. We found, however, that for the analysis of indigenous soil bacterial communities the bead-beating procedure was appropriate because it is fast, reproducible, and gives very pure DNA of relatively high molecular weight. And very importantly, with this protocol the highest soil bacterial diversity was obtained. We believe that the choice of DNA extraction protocol will influence not only the determined phylogenetic diversity of indigenous microbial communities, but also the obtained functional diversity. This means that the detected presence of a functional gene—and thus the indication of enzyme activity—may depend on the nature of the applied DNA extraction procedure.     

玉米单倍体种子胚部特征提取及动态识别方法

为了实现基于机器视觉方法的玉米单倍体种子识别,该文研究了一种玉米单倍体种子胚部特征提取及动态识别方法。采用一种基于B通道平均像素值的胚部特征提取方法,提取了具有Navajo标记的玉米种子的胚部图像,基于此在RGB颜色空间内提取了样本的Navajo标记图像,从而得到一套玉米单倍体种子快速识别RGB组合算法。在玉米分选试验台上进行了动态分选试验。试验结果表明,该算法对LC09124-UH400品种玉米单倍体的识别正确率为98.04%,对杂合体的识别正确率为94.44%。该文提出的玉米单倍体种子RGB组合快速识别算法与玉米分选试验台结合形成的动态分选系统,有助于实现玉米单倍体种子的自动化分选。