Microbial production of docosahexaenoic acid by a low temperature‐adaptive strain Thraustochytriidae sp. Z105: screening and optimization

Abstract

As an alternative source in addition to fish oil, microbial production of docosahexaenoic acid has been recieved more and more attentions owing to their culture advantage. A unicellular eukaryotic microbe with high DHA production and capable of low temperature-adaptive growth was isolated from seawater and identified as Thraustochytriidae sp. Z105. The siginificant effect of temperature on cell growth and DHA synthesis by the strain was revealed. It could grow and produce DHA even at 4 degrees C, but hardly grow above 35 degrees C. Low temperature (15-25 degrees C) was favorable for formation of biomass, lipids and DHA, but DHA synthesis was completely blocked above 30 degrees C. Conditions for high level DHA production by Thraustochytriidae sp. Z105 in flask culture were optimized as follows: medium containing glucose 80 g/l, yeast extract 5.0 g/l, K2HPO(4) . 3 H2O 1.0 g/l, MgSO4 . 7 H2O 0.5 g/l, seawater crystal 20 g/l, pH 6.0, liquid volume 30 ml/250 ml, temperature 20 degrees C, agitation speed of 200 r/min, and culture for 120 h. Under the optimal conditions, biomass of 16.72 g/l, total lipids of 5.35 g/l, DHA yield of 1.71 g/l (accounting for 32% of the total lipids) were achieved, respectively. In flask cluture level, the DHA productivity of Thraustochytriidae sp. Z105 was higher than most reported results, which suggested the wild type strain was a potential superior candidate for industrialization of DHA production. Moreover, the strain is an unique and valuable resource for investigation of the low temperature adaptive mechanism related to DHA synthesis.

Alternative Sources of n-3 Long-Chain Polyunsaturated Fatty Acids in Marine Microalgae

“…Heterotrophic cultivation without light, using inexpensive, well-defined mineral medium supplemented with a carbon source is feasible [46]. However, only a few species have been commercially explored and continuous efforts are made in order to diversify the range of microalgal species used [47]. This implies fermentation studies for growth medium optimization, and improvement of culture conditions and systems, in order to maximize the biosynthesis of n -3 LC-PUFA in each potential strain [48,49].…”

“…The development of an efficient large-scale cultivation system for the commercial production of these nutrients from microalgae would address a major global need [7]. The market for these oils is at the moment limited by supply, hence isolation and exploitation of strains with important n -3 LC-PUFA production potential is on-going [47]. Since the microbial route of oil production through fermentation will always be more costly than potential agricultural alternatives ( i.e ., genetically modified crops), continuous efforts must be made in the sense of reducing production costs while focusing on high-value products with applications in human health [61].…”

Valorification of crude glycerol for pure fractions of docosahexaenoic acid and β-carotene production by using Schizochytrium limacinum and Blakeslea trispora

“…The negative effect of the too high concentration of glycerol on biomass could be attributed to the too high osmotic pressure imposed by glycerol, which has resulted in limited cell growth and product synthesis [ 23 ]. The effect of the initial amount of pure and raw glycerol on improving the production of DHA was investigated with a glycerol concentration ranging from 10 to 120 g/L (Figs.…”

Application of the Response Surface Methodology to Optimize the Fermentation Parameters for Enhanced Docosahexaenoic Acid (DHA) Production by Thraustochytrium sp. ATCC 26185

“…It has been reported that the transformation of saturated fatty acids into unsaturated fatty acids occurred when oil-producing strains grow in oxygen-abundant environments [ 24 ]. The volume of the liquid medium was also noted that DO was affected, thus resulting in a lower DHA yield [ 25 ]. A large volume of liquid medium (more than 40 mL in a 250 mL flask) can also lead to a low DHA yield [ 16 ].…”