The effect of dietary supplementation with Aurantiochytrium limacinum on lactating dairy cows in terms of animal health,productivity and milk composition

The aim of this study was to investigate the effect of dietary supplementation with the docosahexaenoic acid (DHA )‐rich microalgae, Aurantiochytrium limacinum (AURA ), on a variety of health and productivity parameters in lactating cows. Twenty‐four cows were blocked by parity and number of days in milk and then randomly assigned to a control (CON ; n  = 12) group with no algal supplementation, or a treatment group (AURA ; n  = 12) provided with 100 g AURA  cow^?1 day^?1 or 16 g DHA  cow^?1 day^?1. A variety of health and productivity measurements were taken, and results indicated that supplementation had no negative effects on animal health in terms of somatic cell count, haematological and biochemical blood parameters, while body condition was marginally improved by algal supplementation. No differences were found for the various production parameters measured; however, a tendency towards increased milk production was observed for the AURA group during the final stage of the study (+4.5 kg cow^?1 day^?1, day 78–84). The fatty acid profile of milk was improved by supplementation, with significantly lower saturated fatty acids, significantly higher omega‐3 fatty acids and an improved omega‐3/omega‐6 ratio observed when compared to the control group. The amount of DHA in the milk of cows provided 105 g AURA  head^?1 day^?1 was 4.7 mg/100 g milk with a peak transfer efficiency from feed to milk at day 49 of 8.3%. These results indicate that supplementation with 105 g AURA  head^?1 day^?1 resulted in the successful enrichment of milk with DHA without negatively impacting the health or productivity of the animals.     

Effects of a DHA‐rich unextracted microalgae as a dietary supplement on performance,carcass traits and meat fatty acid profile in growing‐finishing pigs

Two 125‐day experiments of the same design were conducted to evaluate the effects of a heterotrophically grown microalgae (AURA) containing docosahexaenoic acid (DHA) on pig performance, carcass traits and the fatty acid composition of lean and adipose tissue. In each experiment, 144 Hypor pigs were blocked by sex, allocated to three treatment groups, and fed 0, 0.25% or 0.50% AURA in isonutritive, isocaloric diets. Pigs were weighed on days 0, 28, 56, 84 and 112. Feed and water intakes were measured every 28 days. Pigs were slaughtered on day 125. Data from the two studies were analysed as a single data set. Performance and carcass traits did not differ between treatments. Both microalgae treatment levels enriched (p < .05) Longissimus lumborum (LL) and backfat in DHA and improved (p < .05) their ratios of n‐6 to n‐3 fatty acids.     

Salt Effect on the Antioxidant Activity of Red Microalgal Sulfated Polysaccharides in Soy-Bean Formula

Sulfated polysaccharides produced by microalgae, which are known to exhibit various biological activities, may potentially serve as natural antioxidant sources. To date, only a few studies have examined the antioxidant bioactivity of red microalgal polysaccharides. In this research, the effect of different salts on the antioxidant activities of two red microalgal sulfated polysaccharides derived from Porphyridium sp. and Porphyridium aerugineum were studied in a soy bean-based infant milk formula. Salt composition and concentration were both shown to affect the polysaccharides’ antioxidant activity. It can be postulated that the salt ions intefer with the polysaccharide chains’ interactions and alter their structure, leading to a new three-dimensional structure that better exposes antiooxidant sites in comparison to the polysaccharide without salt supplement. Among the cations that were studied, Ca²⁺ had the strongest enhancement effect on antioxidant activities of both polysaccharides. Understanding the effect of salts on polysaccharides’ stucture, in addition to furthering knowledge on polysaccharide bioactivities, may also shed light on the position of the antioxidant active sites.     

Digestion of lipids and carbohydrates from microalgae (Chaetoceros muelleri Lemmermann and Isochrysis aff. galbana clone T‐ISO) in juvenile scallops (Pecten maximus L.)

The digestion of laminaran and neutral lipids from the microalgae Chaetoceros muelleri or mixtures of C. muelleri and Isochrysis galbana clone T‐ISO in 4‐mm scallops Pecten maximus were studied. The microalgae were cultivated at fixed low and high growth rate (5% and 60% of μ_max). The cultivation method clearly affected the lipid and carbohydrate contents, as well as their enzyme activity. Chaetoceros muelleri and T‐ISO grown at low growth rate exhibited a considerably higher content of lipids and carbohydrates than those algae grown at high growth rate. The specific activity of laminaranase and neutral lipase was the highest in C. muelleri grown at the low growth rate. Growth rate of scallops was best when they were fed a mono‐species diet of C. muelleri grown at low growth rate. The growth rate of the scallops was positively correlated to the dietary carbohydrate content as well as to the specific activity of neutral lipase and laminaranase in the diet. The capacity to digest carbohydrates (laminaran) might be limiting for the young scallops, and the content of carbohydrates and enzymatic activities of laminaran in the diet should be considered when formulating an optimal diet, both when the diet consist of live microalgae and formulated diets.     

Potential Anti-Obesity,Anti-Steatosis,and Anti-Inflammatory Properties of Extracts from the Microalgae Chlorella vulgaris and Chlorococcum amblystomatis under Different Growth Conditions

Microalgae are known as a producer of proteins and lipids, but also of valuable compounds for human health benefits (e.g., polyunsaturated fatty acids (PUFAs); minerals, vitamins, or other compounds). The overall objective of this research was to prospect novel products, such as nutraceuticals from microalgae, for application in human health, particularly for metabolic diseases. Chlorella vulgaris and Chlorococcum amblystomatis were grown autotrophically, and C. vulgaris was additionally grown heterotrophically. Microalgae biomass was extracted using organic solvents (dichloromethane, ethanol, ethanol with ultrasound-assisted extraction). Those extracts were evaluated for their bioactivities, toxicity, and metabolite profile. Some of the extracts reduced the neutral lipid content using the zebrafish larvae fat metabolism assay, reduced lipid accumulation in fatty-acid-overloaded HepG2 liver cells, or decreased the LPS-induced inflammation reaction in RAW264.7 macrophages. Toxicity was not observed in the MTT assay in vitro or by the appearance of lethality or malformations in zebrafish larvae in vivo. Differences in metabolite profiles of microalgae extracts obtained by UPLC-LC-MS/MS and GNPS analyses revealed unique compounds in the active extracts, whose majority did not have a match in mass spectrometry databases and could be potentially novel compounds. In conclusion, microalgae extracts demonstrated anti-obesity, anti-steatosis, and anti-inflammatory activities and could be valuable resources for developing future nutraceuticals. In particular, the ultrasound-assisted ethanolic extract of the heterotrophic C. vulgaris significantly enhanced the anti-obesity activity and demonstrated that the alteration of culture conditions is a valuable approach to increase the production of high-value compounds.     

Digestibility of the defatted microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon,Salmo salar

The aim of the study was to investigate the apparent digestibility coefficient (ADC) of defatted biomass derived from microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon postsmolts in seawater. Two experiments, one employing cold‐pelleted and the other employing extruded pellets, were carried out to determine the ADC of dry matter (DM), protein, ash and energy. The test feeds consisted of a fishmeal‐based reference feed and the algal biomass, at a ratio of 70:30, and yttrium oxide as the inert marker. The ADC of DM and protein in fish fed microalgae‐incorporated cold‐pelleted feeds were significantly higher for Nannochloropsis sp. compared with Desmodesmus sp. The Nannochloropsis sp. inclusion in extruded feeds also led to higher ADCs of DM and energy compared with Desmodesmus sp. The extrusion processing significantly increased the ADC of ash in both defatted microalgae biomass, as well as ADCs of DM in Nannochloropsis and protein in Desmodesmus sp. In conclusion, the microalga Nannochloropsis sp. was more digestible than Desmodesmus sp., and extrusion processing can be used as a means to improve digestibility of certain nutrients.     

水生环境中细菌与微藻的相互关系及其实际应用

概括了细菌和微藻之间的相互关系及其作用机理,阐述了细菌抑制有害微藻、微藻抑制病原细菌、细菌与微藻协同净化水质的研究进展,并针对水产养殖的实际,提出菌-藻关系研究及开发应用的一些思路。     

南沙群岛海域春、秋季浮游介形类生态学特征

为了解南沙群岛海域春、秋季浮游介形类生态学特征,根据2013年春季(3月中旬至4月初)及秋季(9月)在南沙群岛开展的两个航次生态环境综合调查资料,对该海域浮游介形类生态学特征进行分析研究。结果显示:(1)南沙群岛海域浮游介形类物种组成较为丰富,记录 45种隶属于2科、4亚科、19属。其中,春季有21种,秋季38种,两季均出现的共有种有14个;(2)春、秋两季浮游介形类优势种差异明显,春季优势种组成较为单一,数量低,主要生态类群为外海暖水类群和广温暖水类群,秋季优势种组成较为复杂,数量多,主要为外海暖水类群。春季优势种由后圆真浮萤、葱萤、尖头毛浮萤组成,秋季由纳米海萤、双叉真浮萤、刺喙葱萤、短形小浮萤、粗大后浮萤组成。研究表明:(1)春秋两季浮游介形类密度差异显著,密度分布不均,局部区域密度较高,与该海域局部环流密切相关;(2)浮游介形类两季平均丰富度、多样性指数和均匀度分别为0.59、1.37和0.55,秋季高于春季;(3)春季及秋季均分为岛礁群落和外海群落,群落分布随洋流改变呈季节性变化;(4)受季风影响的大环流及局部环流是浮游介形类种类组成、数量分布及多样性呈明显季节差异的主要因素。     

气升式光生物反应器培养微藻溶氧和pH值变化规律研究

为了解决在光生物反应器养殖微藻过程中,溶解氧和pH值2个培养工艺参数的控制问题,分别在80 L、350 L和900 L的3种规格气升式光生物反应器中培养湛江等鞭金藻(lsochrysis zhanjiangensis),高藻细胞浓度分别达到900×104,700×104,500×104cell/mL,测定其中溶氧和pH值的日变化。结果显示,在光照度4 000 lx以上时,湛江等鞭金藻光合作用强,表现为反应器中藻液溶氧较高,日最高溶氧分别可达17.91 mg/L、15.84 mg/L和12.7 mg/L。所测定的藻液日pH值均在7.00~9.16变化。     

蜡样芽孢杆菌及其生物被膜对有机酸及乙醇的抗性比较

为比较蜡样芽孢杆菌及其生物被膜对环境压力的抗性,该文主要研究了4种有机酸（乙酸、柠檬酸、乳酸和苹果酸）和乙醇对蜡样芽孢杆菌及其生物被膜存活率的影响。结果表明：生物被膜态蜡样芽孢杆菌对乙酸的抗性高于浮游态菌。扫描电镜结果显示,经乙酸处理后,浮游态蜡样芽孢杆菌的细胞表面严重受损,而生物被膜态菌的表面形态未发生明显变化。在柠檬酸、乳酸、苹果酸和乙醇存在的条件下,生物被膜态蜡样芽孢杆菌比浮游态菌表现出更强的压力抗性,特别是在高浓度（有机酸16%～20%,乙醇50%～60%）的情况下,该现象尤为显著。因此,在食品工业中控制被膜态蜡样芽孢杆菌对预防和阻止食品腐败非常重要。该研究结果为实际生产中有效控制蜡样芽孢杆菌及其生物被膜的形成提供参考。