Microalgal bacterial flocs originating from aquaculture wastewater treatment as diet ingredient for Litopenaeus vannamei (Boone)

Microalgal bacterial flocs (MaB‐flocs) in sequencing batch reactors are a novel and promising technology to treat aquaculture wastewater. To improve the economics of this technology, the harvested MaB‐flocs should be valorized. Therefore, we investigated if MaB‐flocs from an outdoor pilot reactor treating pikeperch (Sander lucioperca L.) wastewater can be used as a colour enhancing ingredient for shrimp diets. Considering the nutritional composition and high ash content of MaB‐flocs, five iso‐nitrogenous and iso‐lipidic shrimp diets were formulated by replacing 2–8% of the basal diet ingredients by MaB‐flocs. These diets were continuously fed to juvenile Pacific white shrimps Litopenaeus vannamei (Boone) cultured in a hybrid recirculating aquaculture system. The addition of these relatively low amounts of MaB‐flocs to shrimp diets significantly increased the pigmentation (redness and yellowness) of cooked shrimp tails. The diet modifications did not affect the shrimp survival, weight gain, size distribution and food conversion rate, nor did they affect the proximate composition and fatty acid profile of the raw shrimp muscle. This shows that MaB‐flocs originating from treatment of pikeperch wastewater can substitute 8% of diet ingredients of Pacific white shrimp while enhancing its pigmentation.     

A partial substitution of microalgae with single cell detritus produced from seaweed (Porphyra haitanensis) for the nursery culture of tropical oyster (Crassostrea belcheri)

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 10⁴ cell mL^?1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.     

Nutrient efficacy of microalgae as aquafeed additives for the adult black tiger prawn,Penaeus monodon

This study used a small amount of several lyophilized microalgae (5% of dry weight in aquafeed) to feed adult black tiger prawns Penaeus monodon for 4 weeks, aiming to promote prawn health and nutritional level. Apart from slight increases in ash content, chlorophyll and β‐carotene in the microalgae‐added feeds, there was no difference from the commercial diet in their biochemical composition. After 28 days of feeding, prawn body length, body weight, condition index and also total amount of fatty acids and amino acids of the flesh (2nd abdominal segment) were not affected by microalgae additives as compared with the control commercial diet‐fed group (P > 0.05). Prawns fed the microalgae diets, however, had a relatively better survival rate than those fed the commercial control diet, although no statistical significance was detected in any except for the diatom Melosira sp. The elevated survival rate was concomitant with a higher phagocytosis rate and superoxide dismutase (SOD) activity in the immune response analysis, and significantly a higher astaxanthin content detected in the tail muscle of microalgae diet‐fed prawns (5.36–10.78 ng of astaxanthin per gram of muscle DW). These findings demonstrated that low‐inclusion microalgal additives in prawn diets over a short feeding period (4 weeks) can result in healthier adult prawn, and hence could contribute to the development of an optimized feeding strategy for prawn aquaculture close to harvesting.     

Microalgae as Contributors to Produce Biopolymers

Biopolymers are very favorable materials produced by living organisms, with interesting properties such as biodegradability, renewability, and biocompatibility. Biopolymers have been recently considered to compete with fossil-based polymeric materials, which rase several environmental concerns. Biobased plastics are receiving growing interest for many applications including electronics, medical devices, food packaging, and energy. Biopolymers can be produced from biological sources such as plants, animals, agricultural wastes, and microbes. Studies suggest that microalgae and cyanobacteria are two of the promising sources of polyhydroxyalkanoates (PHAs), cellulose, carbohydrates (particularly starch), and proteins, as the major components of microalgae (and of certain cyanobacteria) for producing bioplastics. This review aims to summarize the potential of microalgal PHAs, polysaccharides, and proteins for bioplastic production. The findings of this review give insight into current knowledge and future direction in microalgal-based bioplastic production considering a circular economy approach. The current review is divided into three main topics, namely (i) the analysis of the main types and properties of bioplastic monomers, blends, and composites; (ii) the cultivation process to optimize the microalgae growth and accumulation of important biobased compounds to produce bioplastics; and (iii) a critical analysis of the future perspectives on the field.     

有益微生物在南美白对虾养殖中的应用研究

目前,应用于南美白对虾养殖的有益微生物主要有微生态制剂、芽孢杆菌、光合细菌、硝化细菌和微藻。概述了5种有益微生物的定义、主要作用机理及应用,同时对有益微生物在南美白对虾养殖中的应用前景提出展望。     

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。     

A New,Quick, and Simple Protocol to Evaluate Microalgae Polysaccharide Composition

In this work, a new methodological approach, relying on the high specificity of enzymes in a complex mixture, was developed to estimate the composition of bioactive polysaccharides produced by microalgae, directly in algal cultures. The objective was to set up a protocol to target oligomers commonly known to be associated with exopolysaccharides’ (EPS) nutraceutical and pharmaceutical activities (i.e., rhamnose, fucose, acidic sugars, etc.) without the constraints classically associated with chromatographic methods, while maintaining a resolution sufficiently high to enable their monitoring in the culture system. Determination of the monosaccharide content required the application of acid hydrolysis (2 M trifluoroacetic acid) followed by NaOH (2 M) neutralization. Quantification was then carried out directly on the fresh hydrolysate using enzyme kits corresponding to the main monosaccharides in a pre-determined composition of the polysaccharides under analysis. Initial results showed that the enzymes were not sensitive to the presence of TFA and NaOH, so the methodology could be carried out on fresh hydrolysate. The limits of quantification of the method were estimated as being in the order of the log of nanograms of monosaccharides per well, thus positioning it among the chromatographic methods in terms of analytical performance. A comparative analysis of the results obtained by the enzymatic method with a reference method (high-performance anion-exchange chromatography) confirmed good recovery rates, thus validating the closeness of the protocol. Finally, analyses of raw culture media were carried out and compared to the results obtained in miliQ water; no differences were observed. The new approach is a quick, functional analysis method allowing routine monitoring of the quality of bioactive polysaccharides in algal cultures grown in photobioreactors.     

微藻EPA和DHA的研究现状及前景

高度不饱和脂肪酸 (ＰＵＦＡ)在营养和医学上的重要作用 ,已引起人们广泛的兴趣 ,特别是二十碳五烯酸 (ＥＰＡ)和二十二碳六烯酸 (ＤＨＡ)两者对防治心脏疾病、动脉硬化、癌症、风湿关节炎、气喘和糖尿病等人类疾病有明显效果[1～ 3 ] ,已成为研究开发的热点。在水产上 ,ＥＰＡ和ＤＨＡ是许多鱼类幼体、对虾幼体、双壳类幼虫的必需脂肪酸 ,关系到幼虫和幼体的生长发育和存活。ＥＰＡ和ＤＨＡ虽然对有些动物不是必需的 ,但在饵料中适当添加这些物质 ,可提高投喂动物的生长速度和存活率[4～ 6] 。目前国内外对微藻中的ＥＰＡ和ＤＨＡ已进行了…     

Supplemental defatted microalgae affects egg and tissue fatty acid composition differently in laying hens fed diets containing corn and flaxseed oil

Effects of defatted microalgae (DFA) on fatty acid composition of eggs and tissues of hens have not been well studied. This experiment was to determine how low concentrations of supplemental DFA in the presence or absence of flaxseed oil (FO) altered fatty acid profiles of egg yolk, liver, adipose tissue, and plasma of layers. A total of 60 Shaver Leghorn layer hens (individually caged, 20-wk old) were allotted into 6 groups (n = 10) and fed a corn/soybean meal basal diet containing 0, 3, or 5% DFA and 0 (1.5% corn oil, CO) or 1.5% FO for 6 wk. BW, ADFI, egg production rate, and egg component weights were not affected by any of the dietary treatments at various time points, but egg yolk color was changed (P < 0.05) with increasing concentrations of DFA. The concentration of n-3 fatty acids in egg yolk and plasma were elevated by FO up to 9-fold (P < 0.05) starting at wk 1 or 2, and 39 to 83% (P < 0.05) by DFA. Supplemental DFA improved (P < 0.05) n-6/n-3 fatty acid ratios in egg yolk and plasma from 13 to 23 and 7 to 13, respectively, only in hens fed diets without FO. Fatty acid profiles of liver and adipose tissue (at wk 6) displayed responses to supplemental DFA and FO similar to those of egg yolk or plasma. In conclusion, supplemental 3 or 5% DFA caused moderate enrichments of n-3 fatty acids and decreased the n6/n3 fatty acid ratios of egg yolk and tissues in hens fed diets without FO.     

四种微藻投喂对三角帆蚌生长、产珠性能、内壳层颜色和微量元素的影响

为筛选三角帆蚌集约化养殖优质的饵料微藻,本实验采用单因子实验方法,探究投喂不同藻(小环藻、小球藻、二形栅藻、旋转单针藻和混合藻)对三角帆蚌生长、产珠性能和内壳珍珠层颜色的影响。结果显示,投喂不同藻对三角帆蚌的生长影响显著,投喂小环藻组三角帆蚌的体质量增重率、壳长、壳宽和壳高增长率最佳。二形栅藻组次之,但壳长增长率略高于小环藻组。小球藻组、旋转单针藻组和混合藻组生长较差。珍珠增重率以小环藻组最佳,显著高于其他4组。小环藻和二形栅藻组珍珠正圆率显著高于旋转单针藻组。不同饵料微藻对斧足和外套膜微量元素含量影响显著,投喂小环藻组斧足中Ca元素含量最高(12 637.30±624.39) mg/kg。不同饵料微藻对内壳色影响显著,小环藻组内壳色亮度最低、色差最小、饱和度较大;混合藻组内壳色亮度最高、色差最大、饱和度最小;二形栅藻组各值处于中间水平。综合考虑,小环藻是三角帆蚌最佳的饵料微藻,二形栅藻次之。