Thraustochytrids of Mangrove Habitats from Andaman Islands: Species Diversity,PUFA Profiles and Biotechnological Potential

Thraustochytrids are the most promising microbial source for the commercial production of docosahexaenoic acid (DHA) for its application in the human health, aquaculture, and nutraceutical sectors. The present study isolated 127 thraustochytrid strains from mangrove habitats of the south Andaman Islands, India to study their diversity, polyunsaturated fatty acids (PUFAs), and biotechnological potential. The predominant strains were identified as belonging to two major genera (Thraustochytrium, Aurantiochytrium) based on morphological and molecular characteristics. The strain ANVKK-06 produced the maximum biomass of 5.42 g·L⁻¹, while ANVKK-03 exhibited the maximum total lipid (71.03%). Omega-3 PUFAs such as eicosapentaenoic acid (EPA) accumulated up to 11.03% in ANVKK-04, docosapentaenoic acid (DPA) up to 8.65% in ANVKK-07, and DHA up to 47.19% in ANVKK-06. ANVKK-06 showed the maximum scavenging activity (84.79 ± 2.30%) while ANVKK-03 and ANVKK-10 displayed the highest antibacterial activity against human and fish pathogens, S. aureus (18.69 ± 1.2 mm) and V. parahaemolyticus (18.31 ± 1.0 mm), respectively. All strains were non-toxic as evident by negative blood agar hemolysis, thus, the thraustochytrids are suggested to be a potential source of DHA for application in the health care of human and fish.     

Antarctic Thraustochytrids as Sources of Carotenoids and High-Value Fatty Acids

Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and carotenoids are needed as human dietary supplements and are essential components in commercial feeds for the production of aquacultured seafood. Microorganisms such as thraustochytrids are potential natural sources of these compounds. This research reports on the lipid and carotenoid production capacity of thraustochytrids that were isolated from coastal waters of Antarctica. Of the 22 isolates, 21 produced lipids containing EPA+DHA, and the amount of these fatty acids exceeded 20% of the total fatty acids in 12 isolates. Ten isolates were shown to produce carotenoids (27.4–63.9 μg/g dry biomass). The isolate RT2316-16, identified as Thraustochytrium sp., was the best producer of biomass (7.2 g/L in five days) rich in carotenoids (63.9 μg/g) and, therefore, became the focus of this investigation. The main carotenoids in RT2316-16 were β-carotene and canthaxanthin. The content of EPA+DHA in the total lipids (34 ± 3% w/w in dry biomass) depended on the stage of growth of RT2316-16. Lipid and carotenoid content of the biomass and its concentration could be enhanced by modifying the composition of the culture medium. The estimated genome size of RT2316-16 was 44 Mb. Of the 5656 genes predicted from the genome, 4559 were annotated. These included genes of most of the enzymes in the elongation and desaturation pathway of synthesis of ω-3 polyunsaturated fatty acids. Carotenoid precursors in RT2316-16 were synthesized through the mevalonate pathway. A β-carotene synthase gene, with a different domain organization compared to the gene in other thraustochytrids, explained the carotenoid profile of RT2316-16.     

Exogenous Antioxidants Improve the Accumulation of Saturated and Polyunsaturated Fatty Acids in Schizochytrium sp. PKU#Mn4

Species of Schizochytrium are well known for their remarkable ability to produce lipids intracellularly. However, during their lipid accumulation, reactive oxygen species (ROS) are generated inevitably as byproducts, which if in excess results in lipid peroxidation. To alleviate such ROS-induced damage, seven different natural antioxidants (ascorbic acid, α-tocopherol, tea extract, melatonin, mannitol, sesamol, and butylated hydroxytoluene) were evaluated for their effects on the lipid accumulation in Schizochytrium sp. PKU#Mn4 using a fractional factorial design. Among the tested antioxidants, mannitol showed the best increment (44.98%) in total fatty acids concentration. However, the interaction effects of mannitol (1 g/L) and ascorbic acid (1 g/L) resulted in 2.26 ± 0.27 g/L and 1.45 ± 0.04 g/L of saturated and polyunsaturated fatty acids (SFA and PUFA), respectively, in batch fermentation. These concentrations were further increased to 7.68 ± 0.37 g/L (SFA) and 5.86 ± 0.03 g/L (PUFA) through fed-batch fermentation. Notably, the interaction effects yielded 103.7% and 49.6% increment in SFA and PUFA concentrations in batch fermentation. The possible mechanisms underlining those increments were an increased maximum growth rate of strain PKU#Mn4, alleviated ROS level, and the differential expression of lipid biosynthetic genes andupregulated catalase gene. This study provides an applicable strategy for improving the accumulation of SFA and PUFA in thraustochytrids by exogenous antioxidants and the underlying mechanisms.     

利用磷脂脂肪酸(PLFAs)生物标记法分析水稻根际土壤微生物多样性

采用磷脂脂肪酸(PLFAs)生物标记法,分析了4个以Ⅱ-32A为母本和3个以制5为父本的系列杂交水稻组合在同等栽培条件下根际土壤的微生物群落结构,并探讨其与水稻特性的内在联系,以期为水稻育种和品种改良提供科学依据。结果表明,水稻根际土壤磷脂脂肪酸生物标记丰富,共检测到38种PLFAs,其中完全分布的生物标记有23种,不完全分布的有15种;水稻根际土壤中PLFAs含量细菌真菌放线菌。不同水稻材料根际土壤微生物磷脂脂肪酸生物标记组成结构存在差异。对根际土壤特征磷脂脂肪酸生物标记16:0(细菌)、18:1ω9c(真菌)、10Me17:0(放线菌)、10Me16:0(硫酸盐还原细菌)和16:1ω5c(甲烷氧化菌)比较可知,制5系列组合含量高,最高的为金生优制5,Ⅱ-32A系列组合较低,含量最低的为Ⅱ优797。对PLFAs总量和水稻特性进行Pearson相关分析,结果表明,PLFAs含量与水稻有效穗数和产量呈显著正相关,但与株高呈显著负相关。对水稻根际土壤磷脂脂肪酸生物量总量进行聚类分析发现,Ⅱ-32A系列组合聚为一类,制5系列组合聚为一类,表现出水稻遗传特性在其根际PLFAs上的差异性。研究结果表明,水稻根际土壤微生物群落PLFAs结构丰富,根际土壤微生物群落结构受水稻遗传亲缘关系的影响。     

Elemental Composition and Cell Mass Quantification of Cultured Thraustochytrids Unveil Their Large Contribution to Marine Carbon Pool

The element stoichiometry of bacteria has received considerable attention because of their significant role in marine ecosystems. However, relatively little is known about the composition of major structural elements of the unicellular heterotrophic protists—thraustochytrids, despite their widely recognized contribution to marine nutrient cycling. Here, we analyze the cell volume and elemental C, N, H, and S cell content of seven cultured thraustochytrids, isolated from different marine habitats, in the exponential and stationary growth phases. We further derive the relationships between the cell volume and elemental C and N content of the cultured thraustochytrids. The cell volumes varied significantly (p < 0.001) among the isolates, with median values of 96.9 and 212.5 μm³ in the exponential and stationary phases, respectively. Our results showed a significantly higher percentage of C (64.0 to 67.5) and H (9.9 to 13.2) but a lower percentage of N (1.86 to 2.16) and S (0.34 to 0.91) in the stationary phase, along with marked variations of C and N fractions among isolates in the exponential phase. The cell C (5.7 to 203.7 pg) and N (0.65 to 6.1 pg) content exhibited a significant (p < 0.001) linear relationship with the cell volume (27.7 to 510 μm³). On further analysis of the relationship across the two growth phases, we found the equation (cell C (pg) = 0.356 × cell volume (μm³) + 20.922) for stationary phase cells more appropriate for C estimation of natural thraustochytrids. This study provides the first experimental evidence of higher cell C density than the current estimate and relatively larger C contribution of thraustochytrids than bacteria to the marine organic pool.     

花生食品脂肪酸组成含量分析

本文主要针对几种市售花生食品的脂肪酸组成含量进行ＧＣ分析，结果表明其脂肪酸组成含量有所差异，花生类食品中主要脂肪酸组成为硬脂酸、油酸，其次为棕榈酸、花生酸、二十碳烯酸、山嵛酸等。在此基础上从营养学的角度进行了分析。     

人造奶油中反式脂肪酸研究概述

反式脂肪酸含量高是制约人造奶油持续发展的重要瓶颈。本文主要从人造奶油中反式脂肪酸的来源、危害及零反式脂肪酸基料油的制备等方面进行概述,为零反式脂肪酸人造奶油产品的开发及市场推广提供理论依据。     

茶籽中脂肪酸的组成及其生物活性脂肪酸对高糖胁迫下RF/6A细胞生长的影响

采用气相色谱(GC)对茶籽的脂肪酸组成进行分析,并研究了活性脂肪酸对高浓度葡萄糖胁迫下RF/6A细胞生长的影响及其与葡萄糖对RF/6A细胞脂肪酸代谢的调节。结果表明,油酸与亚油酸为茶籽中含量最高的脂肪酸;而茶籽中脂肪酸的组成与其品种和产地有密切关系。亚油酸与亚麻酸对高浓度葡萄糖诱导的RF/6A细胞过度增殖有抑制作用。亚油酸、亚麻酸及棕榈酸对RF/6A细胞的脂肪酸代谢均具有调节作用。     

Antibacterial Bicyclic Fatty Acids from a Korean Colonial Tunicate Didemnum sp.

Five new bicyclic carboxylic acids were obtained by antibacterial activity-guided isolation from a Korean colonial tunicate Didemnum sp. Their structures were elucidated by the interpretation of NMR, MS and CD spectroscopic data. They all belong to the class of aplidic acids. Three of them were amide derivatives (1–3), and the other two were dicarboxylic derivatives (4 and 5). The absolute configurations were determined by a bisignate pattern of CD spectroscopy, which revealed that the absolute configurations of amides were opposite to those of dicarboxylates at every stereogenic centers. Compound 2 exhibited the most potent antibacterial activity (MIC, 2 μg/mL).     

市售人造奶油反式脂肪酸含量及物化特性分析

调查分析了市售人造奶油产品的反式脂肪酸含量以及感官、质构、打发性、含水率等物化特性。结果表明,市售人造奶油的质量品质普遍不佳,100%的被检样品含有反式脂肪酸,其中含量最高的达到21.50%;45.83%的被检样品含水率大于16%,不符合国家相关标准。物化分析发现,当熔点为50℃、硬度为4～6 N、粘附性为5～7 mJ、弹性为4.5～6.5 mm时,人造奶油具有较高的感官接受度。     

花生籽仁发育过程中脂肪酸积累规律研究

以高O／L花生品种8130为材料对其籽仁发育过程中脂肪酸的累积过程进行分析。结果显示,花生籽仁中,含有8种主要的脂肪酸,按含量高低依次为油酸、亚油酸、棕榈酸、硬脂酸、山嵛酸、花生酸、二十四烷酸、花生烯酸;花生籽仁发育过程中,油酸含量逐渐增多,其它脂肪酸呈逐渐降低的变化规律。饱满籽仁中亚油酸和油酸含量占全部脂肪酸的80％以上。脂肪酸总量在籽仁发育前期增加迅速,然后缓慢增长,到籽仁成熟期又迅速增加,在收获期达到峰值,油酸亚油酸比值（O／L）,随籽仁发育呈逐渐增加的变化规律,饱满籽仁达到最大。     

Biosynthesis of Polyunsaturated Fatty Acids in Marine Invertebrates: Recent Advances in Molecular Mechanisms

Virtually all polyunsaturated fatty acids (PUFA) originate from primary producers but can be modified by bioconversions as they pass up the food chain in a process termed trophic upgrading. Therefore, although the main primary producers of PUFA in the marine environment are microalgae, higher trophic levels have metabolic pathways that can produce novel and unique PUFA. However, little is known about the pathways of PUFA biosynthesis and metabolism in the levels between primary producers and fish that are largely filled by invertebrates. It has become increasingly apparent that, in addition to trophic upgrading, de novo synthesis of PUFA is possible in some lower animals. The unequivocal identification of PUFA biosynthetic pathways in many invertebrates is complicated by the presence of other organisms within them. These organisms include bacteria and algae with PUFA biosynthesis pathways, and range from intestinal flora to symbiotic relationships that can involve PUFA translocation to host organisms. This emphasizes the importance of studying biosynthetic pathways at a molecular level, and the continual expansion of genomic resources and advances in molecular analysis is facilitating this. The present paper highlights recent research into the molecular and biochemical mechanisms of PUFA biosynthesis in marine invertebrates, particularly focusing on cephalopod molluscs.     

Lipids and Fatty Acids of Nudibranch Mollusks: Potential Sources of Bioactive Compounds

The molecular diversity of chemical compounds found in marine animals offers a good chance for the discovery of novel bioactive compounds of unique structures and diverse biological activities. Nudibranch mollusks, which are not protected by a shell and produce chemicals for various ecological uses, including defense against predators, have attracted great interest for their lipid composition. Lipid analysis of eight nudibranch species revealed dominant phospholipids, sterols and monoalkyldiacylglycerols. Among polar lipids, 1-alkenyl-2-acyl glycerophospholipids (plasmalogens) and ceramide-aminoethyl phosphonates were found in the mollusks. The fatty acid compositions of the nudibranchs differed greatly from those of other marine gastropods and exhibited a wide diversity: very long chain fatty acids known as demospongic acids, a series of non-methylene-interrupted fatty acids, including unusual 21:2∆7,13, and an abundance of various odd and branched fatty acids typical of bacteria. Symbiotic bacteria revealed in some species of nudibranchs participate presumably in the production of some compounds serving as a chemical defense for the mollusks. The unique fatty acid composition of the nudibranchs is determined by food supply, inherent biosynthetic activities and intracellular symbiotic microorganisms. The potential of nudibranchs as a source of biologically active lipids and fatty acids is also discussed.     

Bioprospecting Red Sea Coastal Ecosystems for Culturable Microorganisms and Their Antimicrobial Potential

Microorganisms that inhabit unchartered unique soil such as in the highly saline and hot Red Sea lagoons on the Saudi Arabian coastline, represent untapped sources of potentially new bioactive compounds. In this study, a culture-dependent approach was applied to three types of sediments: mangrove mud (MN), microbial mat (MM), and barren soil (BS), collected from Rabigh harbor lagoon (RHL) and Al-Kharrar lagoon (AKL). The isolated bacteria were evaluated for their potential to produce bioactive compounds. The phylogenetic characterization of 251 bacterial isolates based on the 16S rRNA gene sequencing, supported their assignment to five different phyla: Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, and Planctomycetes. Fifteen putative novel species were identified based on a 16S rRNA gene sequence similarity to other strain sequences in the NCBI database, being ≤98%. We demonstrate that 49 of the 251 isolates exhibit the potential to produce antimicrobial compounds. Additionally, at least one type of biosynthetic gene sequence, responsible for the synthesis of secondary metabolites, was recovered from 25 of the 49 isolates. Moreover, 10 of the isolates had a growth inhibition effect towards Staphylococcus aureus, Salmonella typhimurium and Pseudomonas syringae. We report the previously unknown antimicrobial activity of B. borstelensis, P. dendritiformis and M. salipaludis against all three indicator pathogens. Our study demonstrates the evidence of diverse cultured microbes associated with the Red Sea harbor/lagoon environments and their potential to produce antimicrobial compounds.     

GC-MS测定绿茶及速溶绿茶的游离脂肪酸

以绿茶及速溶绿茶为材料 ,采用硫酸_甲醇甲酯化 ,经GC_MS能够较好地分离和分析茶叶中的游离脂肪酸 ,三氟硼酸甲酯化不适合茶叶脂肪酸的分析。速溶绿茶中游离脂肪酸的含量十分少 ,只有绿茶原料的0 5 %。     

水稻植株及其内生微生物磷脂脂肪酸生物标记异质性

采用改良磷脂脂肪酸法分析水稻植物自身磷脂脂肪酸和其内生微生物磷脂脂肪酸生物标记异质性。结果表明,水稻植株和其内生微生物共有磷脂脂肪酸有直链磷脂脂肪酸20∶0、12∶0、16∶0、18∶0和支链磷脂脂肪酸如18∶3ω6с(6,9,12)、19∶0 CYCLOω8с、15∶1ω6с等,且在水稻中含量均低于30μg/g,在内生微生物中的含量高于30μg/g。水稻内生微生物独有磷脂脂肪酸主要为支链磷脂脂肪酸,共有22种如i20∶0、20∶1ω9с、12∶0 3OH等,含量差异很大,为0.91～11 481.25μg/g。对水稻内生微生物独有磷脂脂肪酸对应分析CA得到,遗传距离近的水稻品种其对应距离也近,CA载荷图显示内生微生物磷脂脂肪酸对应距离小于姨2的为多元分布,即该磷脂脂肪酸分布在多个水稻品种中;大于姨2的为单一分布,即仅在特定的水稻品种中分布,表明水稻内生微生物磷脂脂肪酸分布与水稻品种遗传有关。     

Investigation of Deep-Sea Ecosystems Using Marker Fatty Acids: Sources of Essential Polyunsaturated Fatty Acids in Abyssal Megafauna

Abyssal seafloor ecosystems cover more than 50% of the Earth’s surface. Being formed by mainly heterotrophic organisms, they depend on the flux of particulate organic matter (POM) photosynthetically produced in the surface layer of the ocean. As dead phytoplankton sinks from the euphotic to the abyssal zone, the trophic value of POM and the concentration of essential polyunsaturated fatty acids (PUFA) decrease. This results in pronounced food periodicity and limitations for bottom dwellers. Deep-sea invertebrate seston eaters and surface deposit feeders consume the sinking POM. Other invertebrates utilize different food items that have undergone a trophic upgrade, with PUFA synthesized from saturated and monounsaturated FA. Foraminifera and nematodes can synthesize arachidonic acid (AA), eicosapentaenoic acid (EPA), while some barophylic bacteria produce EPA and/or docosahexaenoic acid. FA analysis of deep-sea invertebrates has shown high levels of PUFA including, in particular, arachidonic acid, bacterial FA, and a vast number of new and uncommon fatty acids such as 21:4(n-7), 22:4(n-8), 23:4(n-9), and 22:5(n-5) characteristic of foraminifera. We suppose that bacteria growing on detritus having a low trophic value provide the first trophic upgrading of organic matter for foraminifera and nematodes. In turn, these metazoans perform the second-stage upgrading for megafauna invertebrates. Deep-sea megafauna, including major members of Echinodermata, Mollusca, and Polychaeta display FA markers characteristic of bacteria, foraminifera, and nematodes and reveal new markers in the food chain.     

染料木素联合多不饱和脂肪酸对MCF-7细胞脂代谢基因表达的影响

选用不同浓度的染料木素(GEN)及二十二碳六烯酸(DHA)作用于MCF-7细胞,研究大豆中抗癌成分染料木素与不同比例的多不饱和脂肪酸(PUFAs)联用,对乳腺癌细胞MCF-7增殖及脂代谢基因表达情况的影响。根据DHA的有效浓度设定亚油酸(LA)及LA∶DHA(10∶1)混合PUFAs作用浓度。将GEN分别与DHA、LA及LA∶DHA(10∶1)联合作用细胞,检测细胞生存率,并通过qPCR方法检测细胞内过氧化物酶体增殖物激活受体γ(PPARγ)、5-脂氧合酶(5-LOX)、环氧合酶-2(COX-2)mRNA表达情况。结果表明:高浓度GEN(300,200,100μmol·L~(-1))及DHA(400,300,200μmol·L~(-1))可抑制MCF-7细胞的增殖,且随着时间增加抑制作用增强。而低浓度GEN(50,25μmol·L~(-1))及LA组及10∶1组对细胞增殖有轻度促进作用。添加GEN的G+L组和G+10∶1组细胞的生存率显著降低,同时GEN可降低G+L组细胞5-LOX mRNA的表达量,且GEN与LA∶DHA(10∶1)联用,增加了细胞内PPARγ mRNA的表达水平并抑制了COX-2 mRNA的表达。试验证实GEN可抑制高比例ω-6 PUFAs对乳腺癌细胞增殖的促进作用,其作用机制主要是通过增加PPARγ mRNA表达,抑制COX-2 mRNA表达水平实现的。大豆的抗乳腺癌作用可能是由于GEN与PUFAs在抑制乳腺癌细胞增殖方面产生了协同效应。     

响应面法优化生产高不饱和脂肪酸大豆油脂

根据Box-Behnken中心组合试验设计原理,在单因素试验的基础上,采用响应面分析法,建立了生产高不饱和脂肪酸大豆油脂的二次多项数学模型,并以产出大豆油脂的碘值为响应值做响应面和等高线,考察了结晶时间、结晶温度、回调时间和回调温度对不饱和脂肪酸含量的影响。通过自制的油脂结晶器,制得富含高不饱和脂肪酸的大豆油脂。得出最佳工艺参数为:降温速度5℃/h,结晶温度-15℃,结晶时间24h,搅拌速度20rpm。利用温度回调至-5℃的方法,使所得油脂产品高不饱和脂肪酸含量达到86.41%。     

Advances in Technologies for Highly Active Omega-3 Fatty Acids from Krill Oil: Clinical Applications

Euphausia superba, commonly known as krill, is a small marine crustacean from the Antarctic Ocean that plays an important role in the marine ecosystem, serving as feed for most fish. It is a known source of highly bioavailable omega-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid). In preclinical studies, krill oil showed metabolic, anti-inflammatory, neuroprotective and chemo preventive effects, while in clinical trials it showed significant metabolic, vascular and ergogenic actions. Solvent extraction is the most conventional method to obtain krill oil. However, different solvents must be used to extract all lipids from krill because of the diversity of the polarities of the lipid compounds in the biomass. This review aims to provide an overview of the chemical composition, bioavailability and bioaccessibility of krill oil, as well as the mechanisms of action, classic and non-conventional extraction techniques, health benefits and current applications of this marine crustacean.