DNA amplicons using arbitrary primers distinguish polymorphic loci among mangrove thraustochytrid genomes

Thraustochytrids - lightly-pigmented estuarine and marine microheterotrophs, taxonomically aligned with heterokont algae - are of great biotechnological interest because they produce substantial amounts of polyunsaturated fatty acids (PUFAs) especially docosahexaenoic acid (DHA:6n3). In this study, twenty-seven strains, isolated from twenty mangrove areas in the Philippine archipelago, were mass-produced in axenic flask cultures using high-glucose medium with continuous agitation. Polymorphic loci of thraustochytrid genomes, determined using four arbitrary primers (OPC02, OPC05, OPC07 and OPC08) in PCR analysis, were randomly amplified as molecular markers for genetic fingerprinting. Electrophoretic banding patterns of DNA amplicons, recognized based on nucleic acid size, were scored on data matrix and analyzed using Jaccard's coefficient and single-linkage hierarchical clustering to characterize degree of genetic relatedness among thraustochytrids. Conclusively, nearest-neighbor dendrogram of randomly amplified polymorphic DNAs (RAPDs) markers classify the strains into two monophenetic clades, representing the two major genera: Schizochytrium and Thraustochytrium

Developmental historicity and saccharide heterotrophy of Schizochytrium sp. OT01: Implication of docosahexaenoic acid production for biotechnological applications

Thraustochytrids have been targeted worldwide in search of highly oleaginous strains for industrial applications and newly collected holotypes are described based on life cycle developmental history and saccharide heterotrophy. Schizochytrium sp. OT01, a novel thraustochytrid protist from Panay, Philippines, distinguished from other reported strains by its asexual reproductive history - including the successive binary division of vegetative cells forming tetrads or octads, granular maturation of thalli into zoosporangia liberating heterokont motile zoospores and transformation of spheroidal thalli into amoeboid cells. Live-cell differential imaging and electron micrographs support its distinctive morphological features, such as hair-like pseudopodial astrals along hyaline margins of mature limaciform amoeboids and in motile zoospores prior to heterokont flagellum elongation. Moreover, its heterotrophic culture on certain saccharides (glucose, fructose, cellobiose, sucrose and starch) in continuously agitated fermentation condition was further investigated to determine hydrocarbon assimilative profiles as deduced from biomass yield and polyunsaturated fatty acid production. Increasing biomass yield was observed in increasing concentrations of saccharides; however, aside from glucose and fructose, a graphical drop of biomass was apparent beyond 15 gL, implying osmotic stress at these levels. Maximum biomass yield was observed at 30 gL- glucose and fructose concentration, reaching to about 6 g/l as expressed in freeze-dried weight of harvested cells, which indicates that OT01 could efficiently absorb and metabolize glucose and fructose compared to other hydrocarbons with relatively greater molecular weights. Even though biomass yield amounts were relatively low in cellobiose, sucrose and starch; however, docosahexaenoic acid (DHA) content in total fatty acids was relatively higher, amounting to 45.23, 46.25 and 48.86%, respectively. Moreover, oleagineity levels in glucose and fructose were highest, with lipid yield amounting to 655.55 and 609.38 mg, respectively, in every gram of freeze-dried weight cells. Consequently, DHA yield was significantly higher in both glucose and fructose, reaching respectively to 492.04 and 478.18 mg per liter of nutrient broth, which indicates higher absorption and metabolism efficiency of monosaccharides into fatty acids.With collaborative efforts of the Mindanao State University - Iligan Institute of Technology, this research was supported by the Southeast Asian Fisheries Development Center (Aquaculture Department) under Project Code FD-03-Y2005T through the Biotech Fund of the National Fisheries Research and Development Institute (Bureau of Fisheries and Aquatic Resources)

Use of thraustochytrid Schizochytrium sp. as source of lipid and fatty acid in a formulated diet for abalone Haliotis asinina (Linnaeus) juveniles

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day−1; DISL: 265 μm day−1) and Diet 2 (SGR: 5.2 % BW day−1; DISL: 255 μm day−1). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet