title: Impact of phosphate concentration on docosahexaenoic acid production and related enzyme activities in fermentation of Schizochytrium sp.
abstract: Docosahexaenoic acid (DHA) is an important and widely used infant food additive. In this study, the effects of phosphate concentration on lipid and especially DHA synthesis in the oleaginous fungi Schizochytrium sp. HX-308 have been investigated in batch cultures. The maximum DHA yield (8.9 g/L) and DHA productivity (148.3 mg/L h) in 0.1 g/L KH2PO4 concentration were higher than the DHA yield (6.2 g/L) and DHA productivity (86.1 mg/L h) in 4 g/L KH2PO4 concentration. Furthermore, differences in related enzyme activities (malic enzyme, glucose-6-phosphate dehydrogenase and NAD(+)-isocitrate dehydrogenase) between phosphate-sufficient and phosphate-limitation conditions were assayed. The results showed that the phosphate-limitation condition could maintain higher activities of malic enzyme and glucose-6-phosphate dehydrogenase in addition to lower activity of NAD(+)-isocitrate dehydrogenase. In addition, glucose-6-phosphate dehydrogenase might be the main supplier of NADPH at the early stage of fermentation while malic enzyme might be the provider at the late stage. This information might explain the regulation mechanism of phosphate limitation for lipid production and be useful for further DHA production enhancement.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing, China.
authors.forename: Lu-Jing
authors.initials: LJ
authors.lastname: Ren
authors.forename: Yun
authors.initials: Y
authors.lastname: Feng
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Liang
authors.initials: L
authors.lastname: Qu
authors.forename: He
authors.initials: H
authors.lastname: Huang
mesh_terms: D002021:Buffers; D004281:Docosahexaenoic Acids / Q000096:biosynthesis*; D010088:Oxidoreductases / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism* / Q000494:pharmacology; D017680:Potassium Compounds / Q000378:metabolism* / Q000494:pharmacology; D058009:Stramenopiles / Q000166:cytology / Q000201:enzymology / Q000254:growth & development*
chemical_list: D002021:Buffers; D010710:Phosphates; D017680:Potassium Compounds; D004281:Docosahexaenoic Acids; C013216:potassium phosphate; D010088:Oxidoreductases