Selection of Culture Conditions and Cell Morphology for Biocompatible Extraction of β-Carotene from Dunaliella salina

Biocompatible extraction emerges recently as a means to reduce costs of biotechnology processing of microalgae. In this frame, this study aimed at determining how specific culture conditions and the associated cell morphology impact the biocompatibility and the extraction yield of β-carotene from the green microalga Dunaliella salina using n-decane. The results highlight the relationship between the cell disruption yield and cell volume, the circularity and the relative abundance of naturally permeabilized cells. The disruption rate increased with both the cell volume and circularity. This was particularly obvious for volume and circularity exceeding 1500 µm³ and 0.7, respectively. The extraction of β-carotene was the most biocompatible with small (600 µm³) and circular cells (0.7) stressed in photobioreactor (30% of carotenoids recovery with 15% cell disruption). The naturally permeabilized cells were disrupted first; the remaining cells seems to follow a gradual permeabilization process: reversibility (up to 20 s) then irreversibility and cell disruption. This opens new carotenoid production schemes based on growing robust β-carotene enriched cells to ensure biocompatible extraction.     

IAA对高盐废水培养微藻生长特性与氮磷去除的影响

废水中高浓度的盐会抑制微藻的生长,通过添加外源植物激素吲哚乙酸(IAA)来促进微藻在盐胁迫下的生长,同时考察不同微藻和盐离子种类对高盐废水培养微藻生长特性与氮磷去除的影响。结果表明,流加模式下培养28 d,小球藻、链带藻、四尾栅藻的最高生物量分别为0.55、0.66、0.75 g/L,总氮和氨氮去除率分别为70.7%、88.5%、79.7%和90.7%、92.6%、92.4%,总磷去除率均达到90%以上。四尾栅藻在模拟高盐废水培养24 d后,高质量浓度IAA(20 mg/L)对其生长效果最好,生物量最高可达0.403 g/L,低质量浓度IAA(≤2 mg/L)对其无明显促进作用甚至抑制生长;高质量浓度IAA(20 mg/L)的总氮和氨氮的去除效果最好,去除率分别为20%和44.1%;总磷去除率为97.2%,其余5组总磷去除率均维持在15%左右。此外,不同种盐条件下四尾栅藻生物量分别为0.667 g/L(空白组)、0.750 g/L(Cl^-组)、0.898 g/L(NH₄⁺组)和1.037 g/L(NH₄     

Carotenoid Production from Microalgae: Biosynthesis,Salinity Responses and Novel Biotechnologies

Microalgae are excellent biological factories for high-value products and contain biofunctional carotenoids. Carotenoids are a group of natural pigments with high value in social production and human health. They have been widely used in food additives, pharmaceutics and cosmetics. Astaxanthin, β-carotene and lutein are currently the three carotenoids with the largest market share. Meanwhile, other less studied pigments, such as fucoxanthin and zeaxanthin, also exist in microalgae and have great biofunctional potentials. Since carotenoid accumulation is related to environments and cultivation of microalgae in seawater is a difficult biotechnological problem, the contributions of salt stress on carotenoid accumulation in microalgae need to be revealed for large-scale production. This review comprehensively summarizes the carotenoid biosynthesis and salinity responses of microalgae. Applications of salt stress to induce carotenoid accumulation, potentials of the Internet of Things in microalgae cultivation and future aspects for seawater cultivation are also discussed. As the global market share of carotenoids is still ascending, large-scale, economical and intelligent biotechnologies for carotenoid production play vital roles in the future microalgal economy.     

Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata

Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L⁻¹ day⁻¹) compared to N-sufficiency (0.11 g L⁻¹ day⁻¹). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.     

3种微藻对池蝶蚌幼蚌的选择滤食与生长的影响

为研究3种不同藻类对池蝶蚌幼蚌的摄食率和生长的影响,进行了普通小球藻、斜生栅藻、舟形藻为影响因素,以养殖产量和相对（体重）生长率为评价指标的正交试验。结果表明：池蝶蚌幼蚌的摄食量在5 h内随着藻类浓度的增加而增加,实验组3、7、9的摄食量明显高于其他实验组;相对生长率（壳长、壳高、壳宽和蚌重）、绝对生长率和养殖产量在9组实验中均变化明显;在试验所设定的水平范围内,舟形藻对养殖产量和相对（体重）生长率影响最大,3种藻类的最佳水平组合是：普通小球藻为250个/mL,斜生栅藻为2.5×104个/mL,舟形藻2.5×104个/mL。     

富含DHA微藻对柴达木福牛生长性能和血清抗氧化指标的影响

本试验旨在研究富含二十二碳六烯酸（C22∶6n-3,DHA）的微藻对柴达木福牛生长性能、体尺指标、屠宰性能和血清抗氧化指标的影响。选用24头健康的24月龄柴达木福牛公牛,随机分为3组,每组8头。试验Ⅰ组（对照组）饲喂基础饲粮,试验Ⅱ和Ⅲ组在基础饲粮中分别添加100和200 g/d的微藻粉。预试期10 d,正试期42 d。测定生长性能、体尺指标、屠宰性能相关指标以及血清中总抗氧化能力（T-AOC）、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）活性和丙二醛（MDA）含量。试验结果表明：①试验Ⅱ组平均日增重（ADG）显著高于对照组（P<0.05）;与对照组相比,试验Ⅱ和Ⅲ组的料重比（A/G）显著降低（P<0.05）,饲粮添加富含DHA微藻对福牛的体尺指标和屠宰性能无显著影响（P>0.05）。②与对照组相比,饲粮中添加微藻可显著提高血清SOD活性和T-AOC （P<0.05）,显著降低MDA含量（P<0.05）;试验Ⅲ组的GSH-Px活性显著提高（P<0.05）。综上,在本试验条件下,添加100 g/d富含DHA微藻可显著提高柴达木福牛的饲料转化率和血清抗氧化能力。     

珠母贝浮游幼虫饵料的研究

研究了湛江等鞭金藻、等鞭金藻OA-3011、亚心形扁藻、小球藻、绿色巴夫藻、面包酵母、光合细菌单独及多种混合投喂对珠母贝浮游幼虫生长、存活和变态的影响.结果表明:单独投喂时湛江等鞭金藻、等鞭金藻OA-3011效果最好,幼虫壳长93 μm时可投喂亚心形扁藻,小球藻、绿色巴夫藻、面包酵母、光合细菌不宜单独投喂;直线铰合期、壳顶幼虫的最适日投饵量扁藻为2 400cell/mL和5 000 cell/mL,湛江等鞭金藻为3 000 cell/mL和5 500 cell/mL,光合细菌为10 000 cell/mL和15 000cell/mL湛江等鞭金藻、亚心形扁藻、光合细菌和绿色巴夫藻混合投喂对浮游幼虫生长、存活和变态有显著提高,出现壳初、眼点、附着和变态时间显著缩短.     

不同发育阶段厚壳贻贝幼虫对类胡萝卜素的吸收和代谢研究

为深入了解饵料微藻中类胡萝卜素在双壳贝类生长发育阶段中的吸收和代谢过程,本试验选择我国重要的滩涂养殖贝类——厚壳贻贝(mytilus coruscus)作为研究对象,采用液相色谱-质谱联用技术(HPLC-MS)分析饵料微藻喂养后的幼虫阶段——担轮幼虫、D形幼虫、壳顶期、眼点期和稚贝期中类胡萝卜素分布和代谢变化。结果表明,在9种饵料微藻中,叉鞭金藻和牟氏角毛藻的总类胡萝卜素含量最高,分别达到1 290.7和1 326.4 mg·kg^-1。外源摄入这两种饵料微藻后,幼虫阶段中共鉴定出5种类胡萝卜素,包括1种新合成类胡萝卜素(贻贝黄素)和4种微藻来源类胡萝卜素(α-胡萝卜素、β-胡萝卜素、岩藻黄酮醇、岩藻黄素),其中岩藻黄素的含量最高,与微藻中岩藻黄素含量高的现象一致。担轮幼虫中未检测到类胡萝卜素,而贻贝黄素仅从壳顶期开始检出。类胡萝卜素的变化与发育阶段呈正相关,从D形幼虫到壳顶期,岩藻黄酮醇、岩藻黄素、α-胡萝卜素和β-胡萝卜素的累积最为迅速,分别增加了20.3、20.3、8.0和1.5倍,并在稚贝期达到最高值。此外,与类胡萝卜素吸收代谢相关的基因ABCA1、SRB1和βCMOOX的表达量均显著上调。其中,参与合成代谢的βCMOOX表达最显著,从壳顶期到稚贝期,其表达量增加了38.2~43.3倍,表明该基因可能参与了壳顶期贻贝黄素的合成。本研究结果为了解贝类生物中类胡萝卜素的生物合成过程及代谢途径提供了基础数据。     

细胞融合法构建EPA和DHA高产异养藻株的研究

利用细胞融合技术，将富含EPA和DHA的自养微藻绿色巴夫藻和生长迅速的异养微藻四鞭藻相融合，并筛选出兼养的融合藻株，融合藻株的聪 脂，EPA，DHA和EPA／DHA等各指标均比异养亲本四鞭藻有较大提高，在兼养条件下生长速率高于亲本微藻，脂肪酸组成以多不饱和脂肪酸为主，而在异养条件下以饱和脂肪酸和单不饱和脂肪酸为主。     

基于开放式培养的微藻生物柴油生命周期环境影响评价

为定量评价以微藻为原料生产的生物柴油生命周期系统产生的各种潜在环境影响,以基于开放式培养的微藻生物柴油为研究对象,应用生命周期分析方法,以1 MJ能量的柴油产品为功能单位,对生产、使用微藻生物柴油产生的环境影响进行了分析。结果表明：微藻生物柴油生命周期最显著的环境影响类型为不可更新资源消耗,其次为光化学烟雾形成,生命周期总环境影响指数为4.63×10-4人当量,较石化柴油降低19.34%,以油菜籽为原料的生物柴油生命周期总环境影响指数是微藻生物柴油的7.19倍,微藻培养与生物柴油制取对生命周期总环境影响指数的贡献分别为27.95%与46.24%。基于开放式培养的微藻生物柴油相对于石化柴油与以油菜籽为原料的生物柴油具有较好的生命周期环境效益,控制微藻生物柴油生命周期环境影响的要点在于减少微藻培养与生物柴油制取阶段的动力消耗。