-
[show abstract]
[hide abstract]
ABSTRACT: Temperature was one of the important environmental factors affecting the biosynthesis of docosahexaenoic acid (DHA; C22:6, ω-3). Generally, a low temperature would slow the strain growth, but promote the accumulation of unsaturated fatty acids. According to this information, the effects of temperature and different two-stage temperature shifting strategies on fatty acid production and DHA content of the marine fungoid protist, Schizochytrium sp. HX-308, were investigated in this study. Finally, the highest DHA percentage was up to 51.98% (per total fatty acids) with the DHA production of 6.05% (per dry cell weight), which was obtained with the method of shifting temperature from 30 °C for 32 h to 20 °C for 12 h.
Applied biochemistry and biotechnology 12/2010; 164(3):249-55. · 1.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The present study focused on improving docosahexaenoic acid (DHA) production by Schizochytrium sp. through N-methyl-N-nitro-N-nitrisiguanidine treatment coupled with ultraviolet radiation based on the metabolic pathway analysis. The activity of glucose-6-phosphate dehydrogenase of the mutant was higher than the parent strain, which indicated that the hexose monophosphate pathway of the mutant was strengthened, and more NADPH was thus produced. Also, the activities of malic enzyme and ATP-citrate lyase in the cell extract of the mutant were higher than the parent strain, which indicated that the screening method increased NADPH and acetyl-CoA supply in vivo effectively. Finally, in the batch culturing of the mutant, 34.84% higher lipid was accumulated with the cell dry weight at the same level compared with the parent strain. Moreover, the DHA percentage of the total fatty acids up to 56.22% was achieved using the mutant, which was 38.88% higher than the parent strain. When the cultures were maintained under appropriate conditions, the final DHA yield was 0.20 and 0.11 g/g dry biomass, for the mutant and parent, respectively.
Applied biochemistry and biotechnology 12/2009; 162(4):935-41. · 1.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Docosahexaenoic acid (DHA) production in Schizochytrium sp. HX-308 was evaluated by detecting enzymatic activities of ATP:citrate lyase (EC 4.1.3.8), malic enzyme (EC 1.1.1.40) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) at different fermentation stages. According to the analysis, a regulation strategy was proposed which reinforced acetyl-CoA and NADPH supply at a specific fermentation stage. DHA content of total fatty acids was increased from 35 to 60% by the addition of 4 g/L malic acid at the rapid lipid accumulation stage. Total lipid content also showed an apparent increase of 35% and reached 19 g/L when 40 mL ethanol/L was added at the late lipid accumulation stage.
Bioprocess and Biosystems Engineering 04/2009; 32(6):837-43. · 1.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Klebsiella oxytoca mutants were isolated from the wild type strain ME-303 after mutagenesis with UV coupled with diethyl sulfate and the following modified proton suicide method. By analyzing the activities of lactate dehydrogenase and phosphotransacetylase involved in lactic and acetic acid formation pathways and batch fermentation, one mutant, ME-UD-3, was isolated that produced 7.8% more 2,3-butanediol than ME-303 with the corresponding byproducts of lactic and acetic acid decreased by 88% and 92%, respectively.
Biotechnology Letters 05/2008; 30(4):731-4. · 1.68 Impact Factor
