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Currently, nearly 36.5 million people live with Alzheimer’s disease worldwide, and acetylcholinesterase inhibition is considered the main treatment strategy against it. Seaweeds (or macroalgae) are a natural source of high-value bioactive compounds and have great potential in the production of health foods/foods, pharmaceuticals, cosmetics, animal feeds, biofertilizers, and biofuels. The most studied and applied seaweed species include red seaweed (Rhodophyta), green seaweed (Chlorophyta) and brown seaweed (Phaeophyta). This study aimed to evaluate the antioxidant and neuroprotective activities of extracts/substances isolated with solvents including ethanol 75o and 96o, water, n-hexane, ethyl acetate under normal and ultrasonic conditions (power 80W, frequency 4.7 kHz and for 1 hour) from 5 economically important seaweed species belonging to genera Caulerpa, Sargassum, Gracilaria, Ulva and Kappaphycus collected in Ninh Thuan and Khanh Hoa provinces, Vietnam. The results have shown that 05/30 extracts and substances (including SaE96S, SaH, SaHW, SaEA and fucosterol) isolated from five seaweed species exhibited high antioxidant activity through the free radical screening method using 2,2-diphenyl-1-picrylhydrazyl (DPPH) (with EC50 values < 5 mg/mL for extracts and EC50 value < 2 mM for substance) in comparison with positive control ascorbic acid (EC50 = 0.015 mg/mL); acetylcholinesterase inhibitory activity using acetylcholinesterase inhibitor screening KIT (with IC50 values of < 200 µg/mL for both extracts and substances), compared with positive control galantamine (with IC50 value of 52,8 µg/mL). The extracts/substances were able to protect the cell against cytotoxity in the C6 alzheimer’s disease cell model induced by amyloid beta-protein fragment (Aβ25-35). The results achieved from this research have proven that the extracts/substances isolated from seaweed species were a potential source of medicinal agents for the prevention and treatment of alzheimer’s disease.

The sea area of the Truong Sa Archipelago, Vietnam - outpost island region of the country has a special geographical location and plays an important role in economic development as well as security and defense of Vietnam. Here, the first time for isolation of heterotrophic marine microalgae is precious. In this paper, the results on isolation, identification, and selection of suitable culture conditions of the strain Thraustochytrium pachydermum TSL10 isolated from the sea area of Spratly Island, Truong Sa Archipelago, Vietnam in 2021 were presented. The optimal culture conditions for the growth of T. pachydermum TSL10 in the flask were M1 medium, 3% glucose, 1% yeast extract and 25 - 28 °C temperature. Dry biomass and lipid content reached the highest levels of 12.54 ± 1.23 g/L and 28.65 ± 1.11 % dry cell weight (DCW), respectively. In a 30 L fermentor, T. pachydermum TSL10 grew well in a medium containing 9% glucose and 1% industrial extract yeast. After 120 hours of cultivation, dry biomass, lipid, protein, carbohydrate, carotenoids, and astaxanthin reached the highest levels of 30.76 ± 1.32 g/L; 22.95 ± 0.28% DCW; 6.65 ± 0.19% DCW, 15.96 ± 0.021% DCW, 178.00 ± 2.43 µg/L, and 8.30 ± 0.28 µg/L, respectively. The fatty acid composition contains mainly omega - 6 and omega - 9 fatty acids, accounting for 21.69% of total fatty acids (TFA) and 34.56% of TFA. The fatty acid profile was mainly dominated by linoleic acid and oleic acid, accounting for 21.54% of TFA and 34.23% of TFA, respectively. The results showed that TSL10 biomass was suitable raw material for screening bioactive compounds.

Fucoxanthin belonging to the carotenoid family has different bioactive properties as anti-oxidant, anti-obesity, anti-diabetic, and anti-cancer effects. This study presents the results of the extraction and purification of fucoxanthin from Sargassum olygocystum Montagne, 1845 using thin-layer chromatography, column chromatography, and high-performance liquid chromatography. Furthermore, this study demonstrated the antioxidant activities, expression of antioxidant enzymes, and inhibition of acetylcholinesterase (AChE) of fucoxanthin. The chemical structure, molecular formula (C42H58O6), and molecular weight (658) of fucoxanthin were determined by nuclear magnetic resonance spectroscopy. Fucoxanthin isolated from S. olygocystum showed no cytotoxic effects, moreover, it showed potent antioxidant activity as assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method (with an IC50 value of 3.42 ± 0.15 mg mL− 1), and AchE inhibitory activity (with an IC50 value of 130.12 ± 6.65 µg mL− 1). At concentrations of 50 and 100 µg mL− 1, fucoxanthin protected against amyloid β-protein fragment 25–35 - induced neurotoxicity on the C6 neuronal cell line with the survival of C6 cells higher than 81.01 and 80.98%, respectively, compared to the control group (59%). Moreover, antioxidant enzyme activity and quantitative PCR analysis revealed that the neuroprotective effect of fucoxanthin, was possibly due to not only regulation of gene expression of antioxidant enzyme (CAT and GPx), ER pathway (caspase-3 and Bax) but also promoting expression of genes involved in PI3K/Akt signaling (GSK-3β), autophagy (p62 and ATG5) and the biosynthesis of ACh (VAChT and ChAT). Therefore, fucoxanthin extracted from the Sargassum olygocystum is a potential feedstock source for the production of health foods with neuroprotective effects.

Heterotrophic marine microalgae Thraustochytrids are commonly found in marine environments, sediments, and decaying mangrove leaves. Their ability to produce high-value products such as docosahexaenoic fatty acids (DHA, C22:6 ω-3), carotenoids, and sterols has gained increasing attention. The products are widely applied in the food, pharmaceutical, and cosmetic industries. In this paper, results on the effect of culture medium on fatty acid composition and pigment content as carotenoid and astaxanthin of Schizochytrium mangrovei TB17 strain biomass were presented. The optimal growth conditions of strain TB17 in the flask were determined including the temperature of 28 oC, the salt concentration of 15‰, glucose as carbon source with the concentration of 3%, yeast extract as nitrogen source with the concentration of 1%. Dry cell weight (DCW) and lipid content of strain TB17 reached highest values of 12.61 ± 0.16 g/L; 34.17 ± 1.92% DCW, respectively, after 120 hours of culture. The content of DHA, docosapentaenoic acid (DPA, C22:5 ω-3) and eicosapentaenoic acid (EPA, C20:5 ω-3) in biomass accounted for 36.66 ± 1.63%; 11.73 ± 1.14% and 0.48 ± 0.01% of total fatty acid (TFA), respectively. The content of total carotenoid and astaxanthin reached 35.86 ± 1.52 µg/g and 7.18 ± 0.21 µg/g DCW after 120 hours of culture. Therefore, the obtained biomass of strain TB17 was sufficient to meet the demand for the production of DHA, DPA, EPA fatty acids as well as the extraction of carotenoids, especially astaxanthin for functional food and other biotechnological applications.

One new indol, N-methoxymethyltryptophol (1), one new phenolic, (2 R)-2-(4-hydroxyphenyl)ethyl 2-hydroxy-3-phenylpropanoate (2) and fifteen known compounds (3–17) were isolated from the methanol extract of the fermentation of marine microalgae Aurantiochytrium sp. SC145. Their structures were elucidated by 1D-, 2D-NMR spectroscopic analysis, HR-ESI-MS, quantum chemical calculation methods and by comparing their NMR data with those reported in the literature. All compounds were evaluated for their antimicrobial activities against microorganisms. Compounds 2, 3 and 11 significantly exhibited antimicrobial activities on all tested Gram-(+), Gram-(-) bacteria and the yeast C. albicans with MIC values ranging from 32 to 256 µg/mL.

Microalgae are known to be a nutrient-rich feed source for many aquatic animals. It is also an important raw material source to exploit high biological activity substances for humans. This is the first study on biological characteristics and algae biomass production from the green microalgae Nannochloris atomus being carried out in Vietnam. In this study, scientific name of the strain N. atomus NT12 based on morphological characteristics and 18S rRNA gene sequence (with accession number MW007766 on the GenBank) was identified. At the best conditions for the growth (i.e. Walne medium, 3 x 106 cells/mL initial cell density, 25 -30oC growth temperature, 60 - 100 µmol/m2s light intensity, pH 7, 30‰ salinity), highest NT12 strain cell density of 30 x 106 cells/mL was obtained after 30 days of culture. The microalgae N. atomus NT12 was also successfully cultured on a pilot scale in the plastic bottle 10 L and closed photobioreactors 20 – 50 L resulting in a high biomass productivity of 209 mg/L/day and a biomass rich in polyunsaturated fatty acids such as oleic acid (C18:1n-9), linoleic acid (C18:2n-6) and α-linolenic acid (C18:3n-3) qualified for the purpose of extraction of value bioactive compounds.

Spirulina cyanobacteria have been widely cultivated to exploit products such as crude protein, vitamins, phycocyanin pigment... with high nutritional and pharmacological values. However, the commercialization of these products is still a challenging issue due to high biomass cost, which is mainly caused by expensive nutrients in the culture medium. In this study, from 11 freshwater S. platensis strains, by culture screening, we found 7 strains being capable of profitable growth on inexpensive seawater with salinity ranging from 5 - 30‰, and selected ST strain as the potential strain for further study. Natural seawater must be pretreated to remove ions that easily cause precipitation of nutrients in the culture medium such as Mg2+, Ca2+, SO42-… before using. The ST strain showed the best growth in the natural seawater medium with 30‰ salinity containing 3 g/L NaNO3, 0.5 g/L K2HPO4, 0.05 g/L FeSO4. This strain reached the highest biomass yield at 0.487 g/L and the specific growth rate (µ) of 0.12 x day-1; protein and phycocyanin contents reached 48.6% and 127 mg/g of dry biomass, respectively. There was no difference in the mentioned above values with biological statistical significance between this medium and SOT medium in distilled water. The ST strain biomass was qualified to be used for the production of functional foods. Results of this study provided scientific basis for the use of marine and brackish waters to produce biomass of this highly economic cyanobacterium.

Thraustochytrium is a heterotrophic marine microalgae genus belonging to the Labyrinthula class, Thraustochytriaceae (Thraustochytrids) family. Recently, studied results have showed that some species/strains of Thraustochytrium genus are potential candidates to produce biomass rich in lipid containing high polyunsaturated fatty acid (PUFAs), especially docosahexaenoic (DHA C22: 6 ω-3), carotenoid, extracellular polysaccharides (EPSs) and enzymes which play a crucial role in human health. Therefore, throughout many decades, numerous studies have been conducted in exploiting bioactive compounds, especially PUFAs. Biomass and PUFAs yield of some strains Thraustochytrium spp. depend on environmental conditions. In this paper, the results on the effects of different culture conditions on the growth of Thraustochytrium aureum BT6 (isolated from coastal regions of Binh Thuan in 2010) in 500 mL erlenmeyer flask and 30 L fermentors is presented. Suitable conditions for the growth of strain BT6 were: Bajpai medium, 2% glucose, 0.5% yeast extract, temperature of 20−28 oC, salt concentration 0.5%; and initial algal cell concentration of 2 g/L. The dry biomass, lipid and DHA contents of strain BT6 in 500 mL erlenmeyer flasks and 30 L fermentor reached the highest levels of 8.56 ± 0.12 and 6.92 ± 0.27 g/L, 18.36 ± 1.15 and 5.50 ± 0.133% DCW, 2.00 ± 0.05 and 0.14 ± 0.01% DCW, respectively, after 4 days of cultivation. Carotenoid content in flask and 30L fermentor achieved 44.45 ± 1.4 and 28.84 ± 1.12 mg/kg DCW, respectively after 4 days of cultivation. Obtained results have indicated that the algae biomass met the requirements in orientation to exploit valuable bioactive compounds.

This study investigated the biomass production process from the laboratory to the pilot scale in order to use the nutrient-rich biomass of the diatom Thalassiosira weissflogii as live feed for white-leg shrimp (Litopenaeus vannamei) at larval stages (zoeal, mysis, and postlarval) and in commercial production in hatcheries in Vietnam. Our results showed that T. weissflogii was successfully cultured in 1–2 L Erlenmeyer flasks, 0.2–3.5 m3 composite tanks, and 6.5 m3 tubular photobioreactors, with the highest cell density of 1.6 × 106 cells mL−1 reached after 6 days of culture. Under optimal culture conditions, the protein, lipid, and carbohydrate contents in this algal biomass were 13.2%, 20.0%, and 10.0% of dry cell weight, respectively. The fatty acid composition contains high amount of palmitic acid (C16:0, 43.11% of total fatty acid), and polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA, C20:5ω-3), approximated 16.5% of total fatty acid. In a 50 L larval rearing tank, at the optimal stocking density of 125 nauplii L−1, the survival percentage (75.55%), the total body length (from 5.376 ± 0.007 to 10.860 ± 0.030 mm), and weight (at from PL1 to PL12 stages) (from 0.145 ± 0.002 to 1.158 ± 0.005 g) of the white-leg shrimp larvae reached the highest values but the metamorphosis time (234 h) was shortest compared with the other stocking densities. Further, adding living T. weissflogii biomass to the diet of white-leg shrimp larvae at the nauplii 6 stage led to an increase in the body length, weight, and survival percentage of white-leg shrimp larvae of 21.17%, 35.7%, and 33% higher compared with those of larvae fed the control diet (without the addition of T. weissflogii), respectively. At the same time, the metamorphosis time of larvae (from Z1 to PL1) decreased by 4 h compared to the control group. In intensive ponds (area of 6400 m2 pond−1), using seed stocks at the postlarvae 12 stage that had been fed T. weissflogii, the final weight, yield, and survival percentage of the shrimp were increased by 7.3%, 14.2%, and 16.3%, respectively, compared with those of the control group. There were no statistically significant differences in the protein and carbohydrate contents in the shrimp flesh among the experimental and control group (p > 0.05). The lipid, omega-3, omega-6, and omega-9 fatty acid contents of shrimp flesh in experiment formula (per 100 g shrimp) were 1.21 g, 72.9 mg, 114 mg, and 86.1 mg, 11%, 29%, 21.6%, and 17.7% higher than that those in control, respectively. The obtained results show the great potential of using T. weissflogii as live feed on white-leg shrimp farms in Vietnam.

Objectives Isolation, structure determination, and antimicrobial activities evaluation of compounds from the methanol extract of the marine microalga Thraustochytrium pachydermum TSL10. Methods Using chromatographic methods to isolate compounds from the methanol extract of the T pachydermum. The chemical structures were elucidated by analyses of HR-ESI-MS and NMR spectral data. The antimicrobial activities of compounds were evaluated using the dilution turbidimetric broth method as the standard protocol published by the Clinical and Laboratory Standard Institute. Results One new sterol, (24 R)-ergosta-7,22-diene-3 β,5 α,9 α-triol (1), and 16 known compounds, ergosta-7,22-diene-3 β,5 α-diol (2), cerevisterol (3), (22 E,24 S)-5 α,6 α-epoxy-ergosta-8(9),22-diene-3 β,7 α-diol (4), ergosterol (5), 5 α,8 α-epidioxyergosta-6,22-diene-3 β-ol (6), linoleic acid (7), 4-((9 Z,12 Z)-octadeca-9,12-dienoyloxy)butanoic acid (8), 1-linoleoyl-sn-glycero-3-phosphocholine (9), cibotiglycerol (10), gingerglycolipid B (11), oleic acid (12), 4-((9Z)-octadec-9-enoyloxy)butanoic acid (13), (2 S)-1- O-(9 Z)-octadec-9-enoyl)-3- O-(6-sulfo-D-quinovopyranosyl)glycerol (14), 6′- O-linoleylsucrose (15), gingerglycolipid C (16), and ( S)-3-stearoyl- sn-glycerol (17) were identified from the marine microalga Thraustochytrium pachydermum TSL10. Sterols 1–6 were found to exhibit significant antimicrobial activities on Gram-( + ) bacteria ( Enterococcus faecalis ATCC29212 , Staphylococcus aureus ATCC25923, and Bacillus cereus ATCC14579) and the yeast ( Candida albicans ATCC10231) with MIC values ranging from 32 to 256 µg/mL. Conclusions The results suggested sterols 1–6 could be potential antimicrobial agents against Gram-( + ) bacteria.

In microalga culturing, one important topic is finding methods of increasing the productivity of algal biomass grown on a large scale. The cultured microalgal biomass must be inexpensive to produce, but rich in the bioactive substances, for use as raw materials for many different purposes, such as functional foods, drugs, pharmaceuticals, cosmetics, and biofuels. Here we present results about the effects of ferulic acid extracted from rice bran on the growth, photosynthetic activity, and valuable substance content of the eustigmatophyte Nannochloropsis oculata. The results showed that ferulic acid is a growth promoter that increases N. oculata biomass. Addition of 100 mg L−1 ferulic acid to the culture medium led to an increase in cell density and specific growth rate (μ; day−1) of N. oculata. These values were 2.52 and 2.02 times higher, respectively, than those in the control group (without the addition of ferulic acid). Moreover, photosynthetic parameters, lipid and carbohydrate contents, and intracellular pigment contents (such as chlorophyll a and carotenoids) in the treated algal biomass tended to be higher than those in the control treatment. This study provides an initial scientific basis for the improvement of algal biomass productivity and metabolite production in safe and sustainable ways with naturally derived substances.

Green macroalgae have gained attention as promising renewable sources for biorefining. Despite the wide potential availability of green macroalgae, their utilization has been limited to ethanol production, hindering their further application. In this study, we report that a bacterium, Halomonas sp. strain BL6 (isolated from a mangrove forest in Bach Long, Nam Dinh Province, Vietnam), produces pyruvate from a saccharified solution of the green seaweed Ulva reticulata and secretes it into the medium. Pyruvate, an important α-oxocarboxylic acid, plays a central role in energy and carbon metabolism in living organisms and is used mainly for the synthesis of various chemicals and polymers or as an ingredient or additive in food, cosmetics, and pharmaceuticals. To investigate the possibility of using U. reticulata from the seashore of Vietnam as biomass feedstock, the chemical composition and saccharification yield of this seaweed were studied. Dry biomass of U. reticulata was found to contain 65.5% carbohydrate, 10.3% protein, 1.8% lipid, and 10.6% ash. Reducing sugar content reached 608.79 mg g−1 of biomass after pretreatment with diluted acid and 24 h of incubation with 50 IU g−1 Viscozyme L. The resulting sugars were fermented by Halomonas sp. strain BL6 to produce pyruvate, and the maximal pyruvate concentration reached 55.23 g L−1 after 72 h of cultivation. This study is the first to report the production of valuable compounds other than bioethanol products, such as pyruvate, from U. reticulata hydrolysate by a Halomonas strain.

In this investigation microalgae Chlorella sp. were isolated and identified from the industrial wastewater. Microalgae species was mass cultivated by using BG11 medium. After 30 days, mixture of Chlorella with different wastewater A, B, C, D, E and F with different ration of Chlorella: wastewater which were 1:6, 1:1, and 2:1. Incubated at room temperature at illuminated area. Dissolved oxygen, TDS, salinity, pH, optical density, oxygen saturation and conductivity were measured for day 0, 10, 20 and 30. For microalgae in wastewater A and C, value of pH, salinity, dissolved oxygen, oxygen saturation, conductivity, salinity and TDS did not change while absorbance value decreased from day 0 to day 30. For wastewater B, D, E and F, the absorbance and pH value increase for all concentration from day 0 to day 30. The highest oxygen saturation after 30 days for wastewater B, D, E and F was at concentration 1:6, 2:1 and 1:1 respectively. The highest dissolved oxygen for wastewater B, D and E was at concentration 1:1 and F was at 2:1. The lowest conductivity, salinity and TDS for wastewater B, C, D and F were all at the concentration of 2:1. The result showed that, Chlorella managed to reduce the salinity for wastewater B, C, D and F, at concentration of 2:1 which were 3.67 %, 4.53 %, 5.4 % and 4.91 % respectively.

The first chemical investigation of the marine microalgae Tetraselmis convolutae is reported. Two phytyl esters, phytyl hexadeca-4,7-10,13-tetraenoate (1) and phytyl palmitate (2), and five other compounds, including phytol (3), hexadeca-4,7-10,13-tetraenoic acid (4), poriferasterol (5), palmitic acid (6), and glycerol (7), were isolated from the extracts of Tetraselmis convolutae. Compound 1 was isolated from nature for the first time, and it showed significant cytotoxic activity against KB, SK-LU-1, MCF7, and HepG2 cancer cell lines with IC50 values in the range of 65.23 ± 6.17–89.81 ± 5.83 μM/mL.

A significant promotion of growth and accumulation of metabolites of freshwater microalga Euglena gracilis was obtained by adding phytic acid to the culture. Phytic acid concentration of 0.05% (v/v) showed a maximum biomass increase of 1.6-fold compared to the control group. Synchronous variation in the content and proportion of photosynthetic pigments was also observed. The total chlorophyll content increased with phytic acid concentration, suggesting the enhanced capacity of absorbing light. Cell length, an important biomarker for E. gracilis, was prolonged to a certain extent under light condition, indicating the state of the cells was more active. Since phytic acid is derived from agro waste of rice bran, it is promising as a low-cost but high-efficient growth promoter of E. gracilis.

Pyruvic acid (pyruvate) is a central intermediate in carbon and energy metabolism in all organisms. It is widely used in the industrial biosynthesis of high - value compounds and food additives. Biotechnological pyruvate production has attracted attention as a potential alternative method of pyruvate synthesis. From 27 soil and mud samples collected from mangrove forests of Cam Ranh, Khanh Hoa province, we isolated 10 bacterial strains belonging to Halomonas genus. Among them, 9 strains were able to synthesis and secreted pyruvate in the culture medium. The maximal pyruvate production was in MC8 strain with value of 0.110 ± 0.015 g/L. MC8 strain was Gram-negative, short rod-shaped, 1,56 ± 0,07 in width, 5,09 ± 0,38 µm in length, non-flagella and nonmotile. MC8 strain was positive for oxidase and catalase activities and reduction of nitrate to nitrite and nitrogen. Cells were able to growth at salt concentrations of from 0.5 to 20%, temperature ranging from 20 to 45ºC and pH ranging from 5 to 12. The major fatty acids of MC8 biomass were C16:0; C18:1w7c và C12:0 3OH. Phylogenetic analyses based on 16S rRNA gene sequencing showed that MC8 strain possessed the highest similarity of 98.5% to the strain Halomonas flava. Based on morphological, biochemical characteristics and 16S rRNA gene sequencing, MC8 strain was identified as H. flava. This is the first study of Halophilic bacteria which is capable of pyruvate synthesis in Vietnam. Thus, these obtained results provided important insights into the production of pyruvate using Halomonas strains.

Invasive species of intertidal algae drew little attention, even though biological invasions have been a concern around the world. The red algal bangiophyte, Phycocalidia tanegashimensis (I. Shinmura) Santianez in Santianez & Wynne, 2020 had been reported from the Southwest Atlantic (Brazil) and Northwest Pacific (Philippines and Japan). The appearance of P. tanegashimensis in Brazil was believed to be a recent introduction from the Indo-Pacific/North Pacific but without conclusive evidence. During a study of the biodiversity of bladed Bangiales in South China and Vietnam, we detected the presence of P. tanegashimensis in these areas using a molecular approach to the identification of the species. New distributional records of P. tanegashimensis were therefore morphologically and molecularly confirmed along the Chinese and Vietnamese coastline (part of the South China Sea) in the present study. Molecular sequence data using rbcL (ribulose bisphosphate carboxylase/oxygenase large subunit), COI-5P (cytochrome oxidase 1), and 18S rRNA genes placed P. tanegashimensis in a clade with P. acanthophora (E.C.Oliveira & Coll) Santianez in Santianez & Wynne, 2020, P. denticulata (Levring) Santianez & M.J.Wynne, 2020, P. suborbiculata (Kjellman) Santianez & M.J.Wynne, 2020 and P. vietnamensis (Tak.Tanaka & Pham) Santianez & M.J.Wynne, 2020 as out-groups. The common morphological characters found in these species, including lobed blades and marginal denticulation, and subtropical/tropical distribution, were discussed in relation to their phylogeny. Haplotype distribution analysis indicated that P. tanegashimensis in Brazil might be an invasive species from the South China Sea. The arrival time of P. tanegashimensis from the South China Sea to Brazil was also discussed.

Astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4-dione) is a known to be valuable carotenoid with strong antioxidant, which has been extensively used in various industries (such as aquaculture, nutraceutical, pharmaceutical, and food). There have been two major sources of astaxanthin: chemical (synthetic) and biological (natural) source. In nature, astaxanthin can be synthesized by plants, crustaceans by-product, bacteria, a few fungi, and green algae, in which microalga Haematococcus pluvialis is an appropriate source of natural astaxanthin exploitation that seems to be gaining potential in the market. Technology for natural astaxanthin production is an expensive process, depending on each producer, in each country. Therefore, continuous efforts were necessary to improve the different culture systems (photobioreactor (PBR) and open pond), culture models (heterotrophic and photoautotrophic), culture methods, harvesting, and astaxanthin extraction processes for enhanced production of astaxanthin-rich biomass and cost reduction in large-scale culture. In this chapter, we summarized about astaxanthin production and technology for its production in Vietnam and other Asian countries to get a more general view of this valuable product.

In this study, the genome of Thraustochytrium sp. TN22, a heterotrophic marine microalga, was sequenced, assembled and annotated using the Illumina NovaSeq 6000, PacBio RS II and MinION platform to identify genes and EPS and carotenoid biosynthesis pathways. The genome of Thraustochytrium sp. TN22 consists of 38,842,079 bp with a G + C content of 66.52% and reached 90.7% gene completeness. In total, 15,208 genes were annotated, among which 14,236 genes were identified using the NCBI-nr, KEGG, GO, COG and InterProScan databases. Pathway analysis showed that EPS biosynthesis in Thraustochytrium sp. TN22 follows an ABC-dependent pathway. The carotenoids of Thraustochytrium TN22 are predicted to be synthesized via the mevalonate pathway, and the conversion of β-carotene to xanthophyll proceeds through β-cryptoxanthin and zeaxanthin intermediates. Our results will be useful for improving high-value coproducts for industrial application of thraustochytrids.

Pyruvic acid (pyruvate) the most important α-oxocarboxylic acid, plays a central role in energy metabo-lism in living organisms. It is used mainly as a starting material in the biosynthesis of pharmaceuticals as well as employed in the production of crop protection agents, polymers, cosmetics and food additives. Four Gram-negative, moderately halophilic, pyruvate and poly (3-hydroxybutyrate)- producing strains were isolated from soil samples collected from mangrove forest at Giao Thuy, Nam Dinh province. Preliminary screening results showed that among fours strain, the ND7 strain was able to produce the highest bioplastic-poly (3-hydroxybutyrate) (PHB) and extracellular secretion of pyruvate, respectively, reaching 50.23% dry weight and 6.87 g/L after 60 hours of cultivation. When cultured in high alkaliphilic medium (pH 9.4), the pyruvate secretion increased significantly (21.02 g/L after 60 hours of cultivation). Based on the morphological, bio-chemical characteristics and nucleotide sequence analysis of partial 16S rRNA gene, the ND7 strain was iden-tified as Halomonas maura. The results allow us to conclude that ND7 strain is a potential target for the ex-ploitation of pyruvate in a larger scale.

The green alga Chlamydomonas reinhardtii is a model organism for studying mechanism of the body in response to changes in environmental conditions, photosynthesis as well as chloroplast biogenesis and can be modified to produce high value proteins. In this study, we present results on the selection of cultural conditions for the growth of cell wall - deficient mutant C. reinhardtii (503 strain- control) and recombinant 503-2 strain expressing VP28 protein of White Spot Syndrome Virus (WSSV) in 250 ml flasks. Suitable conditions for the growth of both control and recombinant strains were TAP medium, temperature of 25 C, pH = 7, light intensity of 2 klux, C source - Trisbase, N source - nitrate and salinity of 50 - 100 mM. In these conditions, maximum cell density of the control and recombinant strains was 3.20 ± 0.08 x 106 and 2.96 ± 0.17 x 106 cells/ mL after 3 and 7 days of cultivation, respectively. The presence of vp28 gene in the recombinant microalgal strain was stably maintained at all levels of culture. The results of this paper will be a scientific basis for culturing the recombinant C. reinhardtii to obtain algal biomass which had high expression of surface VP28 protein of WSSV’s envelope for edible vaccine production vaccine by feeding in order to prevent white spot disease of shrimp.

Recently, heterotrophic marine microalga Schizochytrium mangrovei has been shown to be rich in omega 3-6 fatty acids, mainly docosahexaenoic acid (DHA), ecosapentanoic acid (EPA) and docosapentanoic acid (DPA). These fatty acids play an important role on human health. In this article, we presented results of safety assessment and pharmacological effect of Algal Oil Omega 3-6 (AOO-3-6) which made from oil of S. mangrovei TB17 on the experimental animals after 90 days of use. The results of acute toxicity study showed that by oral administration of the AOO-3-6 on white mice at the highest dose of 15.27 g total of DHA, EPA, DPA / kg of whole body of mice/ day (the dosage was 113.63 times higher than the mice dose), the LD50 was not determined. It means that AOO-3-6 capsules was no signs toxicity. At doses of 78.4 mg and 352.8 mg of total of DHA, EPA, DPA/ kg of whole bode of rat/ day (effec-tive dose znd 4.5 times higher than the expected dose) for 90 continuous days on the mice didn’t affect the normal increment of body weight, hematological indices, biochemical indicators; function of liver and kid-ney; histopathology of liver, kidney, spleen of white rats. At the same time, at doses of 134.4 and 403.2 mg total of DHA, EPA and DPA/kg of body weight/day improved the ability to learn, remember on the mice. In addition, it also allowed building its reflexes sustainability in finding food to be faster with shorter reflectance time. As a result, AOO-3-6 capsules are safe and have the ability to improve memory, learning ability on the mouse which can be used for functional food for human health.

Schizochytrium mangrovei strain PQ6 was investigated for coproduction of docosahexaenoic acid (C22: 6ω-3, DHA) and squalene using a 30-L bioreactor with a working volume of 15 L under various batch and fed-batch fermentation process regimes. The fed-batch process was a more efficient cultivation strategy for achieving higher biomass production rich in DHA and squalene. The final biomass, total lipid, unsaponifiable lipid content, and DHA productivity were 105.25 g · L-1 , 43.40% of dry cell weight, 8.58% total lipid, and 61.66 mg · g-1 · L-1 , respectively, after a 96 h fed-batch fermentation. The squalene content was highest at 48 h after feeding glucose (98.07 mg · g-1 of lipid). Differences in lipid accumulation during fermentation were correlated with changes in ultrastructure using transmission electron microscopy and Nile Red staining of cells. The results may be of relevance to industrial-scale coproduction of DHA and squalene in heterotrophic marine microalgae such as Schizochytrium.

Soybean (Glycine max (L) Merr.) is one of the major crops grown worldwide for human food and animal feed. Nanotechnology is one of the most potential tools in modern agriculture to improve crop productivity. In this paper, we investigated the effect of single and mixture cobalt nanoparticles on the change of photosynthesis - related parameters and antioxidant enzyme activity of soybean Glycine max (L) Merr “DT26” at different growth stages under pilot scale. The results showed that all form of cobalt nanoparticles treatment enhanced the photosynthesis of soybean by increasing the content of chlorophyll a, Pn and the ratio of Fv/Fm. These values tended to increase and reached the maximum value at fifth trifoliate stage and then decreased at the beginning bloom stage. The activity of antioxidant enzymes such as superoxide dismutase and peroxidase (when seeds were treated with USA single colbalt nanoparticles at concentration of 16.67 mg/kg) and catalase (with USA single colbalt nanoparticles at concentration of 0.17 mg/kg) were increased in 2.11, 1.85 and 1.60 times respectively compared to the control group (without the treatment of colbalt nanoparticles) while ascorbate peroxidase was reached highest value (increased in 2.73 times) under the condition of Vietnam single colbalt nanoparticles at the dose of 0.17 mg/kg seeds. This suggests that cobalt nanoparticles treatment has generated oxidative stresses and soybean DT26 has the self-protection mechanism by increasing the activity of antioxidant enzymes in order to reduce the amount of H2O2 and O2 which accumulates in the leaf cells.

White spot syndrome virus (WSSV) is the leading cause of shrimp mortality in farms all over the world. In Vietnam, for the last five to ten years, WSSV has always been among the top causes of diseases and loss in our shrimp aquaculture. VP28 and VP26 are two capsid proteins of WSSV that commonly used as biomarkers for diagnosis and target antigens for vaccine against WSSV. Recombinant VP28 (rVP28) has been studied and expressed in various expression systems including E. coli, yeast and baculovirus. rVP28 expressed in these systems showed effective protection against WSSV in shrimps, though there remains limitation on expression efficiency and safety. Recently, green microalgae Chlamydomonas reinhardtii has been widely used to express pharmaceutical proteins and edible vaccines for aquaculture thanks to its advantages as a safe and efficient host. C. reinhardtii is also used as nutrious natural food for shrimps due to its benefits towards shrimp health and growth. In this study, the codons of vp28 gene was adapted and chemically synthesized, and transformed into the nucleus genome of C. reinhardtii using electroporation. The presence of a codon optimized vp28 gene in C. reinhardtii genome was confirmed by colony PCR and sequencing; and its expression level was examined by RT-PCR. These results proved our success in creating transgenic C. reinhardtiii expressing rVP28 and set the foundation for our future research on edible vaccine against WSSV for shrimp.

White Spot Syndrome Virus (WSSV) is a major cause of mortality in shrimp cultivation on farms all around the world. The serious monetary losses related with its occurrence in susceptible shrimps and the limitations of current methods used to treat WSSV disease in Vietnam, highlight the need for new methods to prevent and to manage the disease. The current study investigates the possibility of expressing the VP28 protein of WSSV from the nucleus of Chlamydomonas reinhardtii for WSSV control. The VP28 protein of WSSV was successfully expressed in C. reinhardtii as confirmed by Western blot analysis and RT-PCR. The immunological parameters analyzed in shrimp administered with 4 mg of dried algae (~ 6 × 107 cells)/1 g shrimp showed a high-level expression of lysosome (LSZ), anti-lipopolysaccharide factor (ALF), superoxide dismutase (SOD) and prophenoloxidase (proPO) compared to the control group. The result of oral administration experiments indicated that vaccinated shrimp survived up to 70% of the time as opposed to control group with 100% mortality. Taken together, the result indicated that recombinant C. reinhardtii expressing VP28 has a potential utility as an oral vaccine candidate against WSSV.

Squalene is currently known as chemopreventive agents in reducing the incident of coronary heart disease and cancer. It is also a strong antioxidant used extensively in the food and cosmetic industries. Microbial sources of squalene are being explored in recent years. The objective of this study was to investigate fermentation conditions of Schizochytrium mangrovei PQ6 for high squalene production in 30L bioreactor. Squalene production was influenced by various nutritional factors such as glucose, nitrogen, vitamins etc. and physical factors such as batch and fed-batch fermentation. Our study established that fed-batch fermentation with nitrogen source of 1.2% yeast extract and 6.4% monosodium glutamate and 0.4% mixture of vitamin B1, 6 and 12 as optimal culture condition for maximal production of squalene by S. mangrovei PQ6. In fed-batch culture, the glucose concentration feeding was added up to 22% into the culture at 36 h of fermentation. The maximum squalene production was achieved 6.9 ± 0.1 g/L at 48 h of fed-batch fermentation, respectively. The values were 2-3 times more than that in fed-batch cultivation without adding mixture of vitamins and 4-6 times more than that in batch cultivation. Our obtained results are a breakthrough for the development of alternative squalene source from heterotrophic marine microalgae of Schizochytrium mangrovei PQ6 species for health-promoting functional foods. Citation: Nguyen Cam Ha, Hoang Thi Minh Hien, Le Thi Thom, Hoang Thi Huong Quynh, Dang Diem Hong, 2017. Optimization of fermentation conditions for squalene production by heterotrophic marine microalgae Schizochytrium mangrovei PQ6. Tap chi Sinh hoc, 39(3): 349-358. DOI: 10.15625/0866-7160/v39n3.9130. *Corresponding author: hoangminhhien@yahoo.com; ddhong60vn@yahoo.com Received 6 January 2017, accepted 20 August 2017

In recent years, producing bio-oil from microalgae has gained increasing interest. Schizochytrium mangrovei is a heterotrophic marine microalga that is capable of producing high levels of biomass and lipid. In this study, S. mangrovei strain TB17 was investigated for production of bio-oil consist of omega 3-6 fatty acids using different methods, including a one-stage (direction transesterification of biomass) or a two-stage method (crude oil extraction followed by transesterification). In the one-stage method, omega 3-6 fatty acid alkyl esters (FAAE) extracted from dried biomass reached to 96.36% of total fatty acids (TFA), and 12.71% of dry cell weight (DCW) in which content of docosahexaenoic acid (C22: 6ω-3, DHA), eicosapentaenoic acid (C20: 5ω-3, EPA) and docosapentaenoic acid (C22: 5ω-6, DPA) was accounted for 85.01% of TFA. However, using fresh biomass as feedstock was resulted in lower yield of FAAE (90.95% of TFA and 3.26% of DCW). In the two-stage method, when fresh and dried biomass were used as feedstock, omega 3-6 free fatty acids (FFA) were obtained with equivalent yield (99.07% and 99.83% of TFA; 17.09% and 14.85% of DCW, respectively) with DHA, EPA and DPA contents accounting for over 80% of TFA. Thus, fresh biomass could also be used to extract bio-oil instead of dried biomass. These results would contribute to reduce manufacturing cost of the bio-oil rich in omega 3-6 fatty acids from Schizochytrium in the future. Citation: Le Thi Thom, Nguyen Cam Ha, Dang Diem Hong, 2017. Extraction of bio - oil rich in omega 3-6 fatty acid using different methods from heterotrophic marine microalga Schizochytrium mangrovei. Tap chi Sinh hoc, 39(3): 359-366. DOI: 10.15625/0866-7160/v39n3.9829. *Corresponding author: ddhong60vn@yahoo.com Received 18 May 2017, accepted 20 August 2017

Phototrophic dinoflagellates of the genus Symbiodinium (= zooxanthellae) are well known as symbionts of corals. They play an important role in maintaining the healthy as well as establishment of new reefs. In addition, products such as toxins or pigments from these symbiotic microalgae are potentially important for applications in the biomedical sciences, especially in new drug development. In this study, we isolated successfully a symbiotic microalga from soft coral Sinularia sp. which was collected in Cu Lao Cham coastal waters of Quang Nam province. Based on morphological characteristics and 18S rRNA gene sequences, isolated SHM8 strain was identified as Symbiodinium goreaui. This symbiont was cultured in different media such as ASP-A8, F2, ES, IMK, K, and L1. L1 culture medium supplemented with taurine concentration of 4.88 mM led to the cell density of SHM8 strain increased in 50% compared to control on day 2 in cultivation; amino acid mixture enhanced cell density by 31.7% on day 5 in cultivation. Supplementation of carbon source (bicarbonate salt of 16.8 g/L) and nitrogen source (nitrate salt of 0.055 g/L) enhanced the cell density by 40% and 27%, respectively on day 6 in culture. Obtained results in this study proved that this microalga can live independently without host. Successful isolation and cultivation of Symbiodinium microalga are one of the necessary conditions for promising researches on the natural bioactive substances from this microalgal biomass in the future in Vietnam. Citation: Dang Diem Hong, Pham Van Nhat, Hoang Thi Huong Quynh, Luu Thi Tam, Ngo Thi Hoai Thu, Nguyen Cam Ha, Hoang Thi Lan Anh, Nguyen Hoai Nam, Nguyen Thi Minh Hang, Chau Van Minh, 2017. Study on biocharacteristics of Symbiodinium sp. isolated from soft coral in coastal water of Quang Nam, south central Vietnam. Tap chi Sinh hoc, 39(3): 367-375. DOI: 10.15625/0866-7160/v39n3.10112. *Corresponding author: ddhong60vn@yahoo.com Received 19 June 2017, accepted 20 August 2017

Seaweed aquaculture beds (SABs) that support the production of seaweed and their diverse products, cover extensive coastal areas, especially in the Asian-Pacific region, and provide many ecosystem services such as nutrient removal and CO2 assimilation. The use of SABs in potential carbon dioxide (CO2) mitigation efforts has been proposed with commercial seaweed production in China, India, Indonesia, Japan, Malaysia, Philippines, Republic of Korea, Thailand, and Vietnam, and is at a nascent stage in Australia and New Zealand. We attempted to consider the total annual potential of SABs to drawdown and fix anthropogenic CO2. In the last decade, seaweed production has increased tremendously in the Asian-Pacific region. In 2014, the total annual production of Asian-Pacific SABs surpassed 2.61 × 106 t dw. Total carbon accumulated annually was more than 0.78 × 106 t y−1, equivalent to over 2.87 × 106 t CO2 y−1. By increasing the area available for SABs, biomass production, carbon accumulation, and CO2 drawdown can be enhanced. The conversion of biomass to biofuel can reduce the use of fossil fuels and provide additional mitigation of CO2 emissions. Contributions of seaweeds as carbon donors to other ecosystems could be significant in global carbon sequestration. The ongoing development of SABs would not only ensure that Asian-Pacific countries will remain leaders in the global seaweed industry but may also provide an added dimension of helping to mitigate the problem of excessive CO2 emissions.

Halophilic bacteria are receiving increasing attention for industrial chemical production processes due to their unique properties. Herein, an alkaliphilic and halophilic bacterium was isolated from a commercial Spirulina culture at Nghe An province in Vietnam and found to secrete pyruvate. Pyruvate is widely used as a starting material in the industrial biosynthesis of pharmaceuticals, and is employed for production of crop protection agents, polymers, cosmetics, and food additives. Phenotypic and chemotaxonomic characterization, and the 16S rRNA gene sequence homology with Halomonas hydrothermalis strain DSM 15,725 (99.2%) predicted that the strain belongs to the Halomonas genus, thus we named this strain as H. hydrothermalis strain C22. We investigated the biocharacteristics and capacity of strain C22 and determined the draft genome sequence comprising 3,934,166 bp with a G + C content of 60.2% encoding 3,668 proteins, 58 tRNAs, 9 rRNAs, and 1 tmRNA. Maximal pyruvate secretion reached 51.1 g/l after 84 h of cultivation. The results will facilitate future studies on the genetic and metabolic diversity of halophilic bacteria and expand our understanding of important bioprocesses in this microorganism.