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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.

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.

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.

Schizochytrium mangrovei PQ6 contains many important polyunsaturated fatty acids, such as docosahexaenoic acid (DHA, C22: 6w-3), eicosahexaenoic acid (EPA, C20: 5w-3) and docosapentaenoic acid (DPA, C22: 5w-6). These fatty acids are essential for survival and growth of many marine fish larvae. In this paper, fresh biomass of S. mangrovei PQ6 was used for culturing rotifer Brachionus plicatilis. In the first formula (L1), rotifers were fed on baker’s yeast; in second formula (L2), rotifers were fed on mixed two microalgae, Nannochloropsis oculata and Chaetoceros gracilis; in the third formula (L3), rotifers were fed on S. mangrovei PQ6 biomass. The results indicated that S. mangrovei PQ6 biomass can replace baker’s yeast and autotrophic microalgae in feeding rotifers. Total lipid, total fatty acid and polyunsaturated fatty acid contents of rotifers fed on formula 3 (S. mangrovei PQ6) were higher than those within others. High polyunsaturated fatty acid (C ≥ 20) in omega-3 and 6 groups; DHA and DPA contents of rotifers fed on S. mangrovei PQ6 were the highest, accounting for 39.81% of total fatty acid; 41.95% and 8.24% polyunsaturated fatty acids, corresponding to 20.52; 12.15 and 2.4 mg/g of dried weight, respectively.The survival rate of black sleeper’s larvae was highest when they were fed on rotifers grown on L3 formula (51.20 ± 0.89%), followed by L2 formula (48.70 ± 2.67%) and the lowest with L1 formula (43.44 ± 1.54%) (P < 0.05). However, among three formulas, no significant difference was found in the growth of black sleeper’s larvae (P > 0.05). These results suggest that biomass of S. mangrovei PQ6 can replace traditional feed like autotrophic microalgae or baker’s yeast for biomass culture of the Brachionus plicatilis rotifer for rearing black sleeper’s larvae to enhance seed quality to meet demands of market.

Marine microalga Isochrysis sp. was isolated from Hai Phong area of Vietnam coastal zone. Their pure cultures were raised in the laboratory for culture optimization, molecular identification and biochemical analysis. Based on the morphological studies the newly isolated species was identified as Isochrysis galbana Parke and was confirmed by 18S rRNA gene analysis. The nucleotide sequence of partial 18S rRNA gene was submitted to the GENEBANK with accession number FJ536744. Optimum conditions for growth of the species was f/2 medium at temperature 25 ± 1°C, salinity 30 ± 1 psu, pH 7.0 and light intensity of 100 μmol m−2 s−1. Under these optimum conditions, the content of protein, carbohydrate and total lipid were 27.981 ± 0.892%, 25.263 ± 0.789% and 9.780 ± 0.120% of dry cell weight, respectively (equivalent 38.768 ± 0.892%, 35.000 ± 0.789% and 13.550 ± 0.120% of ash free dry weight). I. galbana Parke, strain HP has the highest content of docosahexanenoic acid (DHA), up to 14.7% of total fatty acid and maximal polyunsaturated fatty acids (PUFAs) values at the early stationary phase in f/2 medium. The n-3 and n-6 PUFA ratio (n-3/n-6) of strain HP was from 4.50 to 5.69 at different phases of growth curve. These results suggest that biomass of this strain can be used as live feed in aquaculture.

This work is to explore the potential of producing biodiesel and valuable co-products from the biomass of Schizochytrium mangrovei PQ6 which was isolated from Phu Quoc Island, Kien Giang province, Vietnam. This microalga contains high lipid content (up to 70% of dry cell weight) and high level of total fatty acids, which is ideal for making biodiesel. The production of fatty acid methyl esters (FAME) from this marine microalga resulted in a yield of 88% based on algal oil and 44% based on algal biomass. The process of separating the obtained FAME into a first fraction enriched with saturated FAME (SFAME) and a second fraction enriched with unsaturated FAME (UFAME) was then investigated to exploit the valuable co-products. The obtained results shown that the mass fraction of SFAME and UFAME were 70% and 30%, respectively. The UFAME fraction contains a high content of DHA (accounting for 69.000% of TFAs). The test results of the SFAME fraction indicated that specific gravity at 15°C, flash point, water and sediment, kinematic viscosity at 40°C, sulfated ash, sulfur, copper strip corrosion at 50°C, cetane number, carbon residue, iodine number, workmanship meet Vietnam Biodiesel B100 Standard. Moreover, the utilization of waste glycerol from biodiesel process as carbon source for the cultivation of the microalgae S. mangrovei PQ6 and Spirulina platensis was also investigated.

The heterotrophic marine microalga, Schizochytrium mangrovei PQ6, synthesizes large amounts of polyunsaturated fatty acids (PUFAs) with possible nutritional applications. We characterized the transcriptome of S. mangrovei PQ6, focusing on lipid metabolism pathways throughout growth. Cell growth, total lipid, and docosahexaenoic acid (DHA, 22:6n-3) contents of S. mangrovei PQ6 in 500 ml batch cultures rapidly increased on day 1 in cultivation and reached their maximum levels on day 5. Maximum lipid accumulation in 500 ml batch cultures occurred on day 5, with total lipid and DHA contents reaching 33.2 ± 1.25% of dry cell weight (DCW) and 136 mg/g DCW, respectively. 11,025 unigenes, 28,617 unigenes and 18,480 unigenes from the transcriptomes of samples collected on day 1, 3, and 5 in cultivation were identified, respectively. These unigenes of the three samples were further assembled into 30,782 unigenes with an average size of 673 bp and N50 of 950 bp, and a total of 9,980 unigenes were annotated in public protein databases. 93 unigenes involved in lipid metabolism in which expression patterns corresponded with total lipid and DHA accumulation patterns were identified. The possible roles of PUFAs pathways, such as those mediated by fatty acid synthase, polyketide synthase, and desaturase/elongase, co-exist in S. mangrovei PQ6.