PMC:4301621 / 21176-22529 JSONTXT

{"project":"2_test","denotations":[{"id":"25582171-10099624-14905496","span":{"begin":1002,"end":1004},"obj":"10099624"}],"text":"Both the maximum and minimum flux of oxygen absorption of DGLA, ARA and EPA production in silico were found to be 1.552, 1.674 and 1.891 mmol gDW−1 h−1 respectively, using FVA. This indicated that the degree of PUFA unsaturation was dependent on oxygen content. Robustness analysis was used to elucidate the effects of oxygen uptake rate on PUFA biosynthesis. The oxygen uptake rate was perturbed by constraints-based flux analysis between 0 and 20 mmol gDW−1 h−1. The minimum growth rate was set at 0.03 h−1, with ARA exchange reaction as the objective function. When oxygen absorption was lower than 2.0 mmol gDW−1 h−1, ARA production increased with oxygen absorption rate (Additional file 5a). However, beyond this range, ARA production gradually declined with increasing oxygen uptake rate. As reported by Higashiyama et al., when the DO concentration range was 10-15 ppm, the ARA yield was enhanced 1.6-fold over a DO of 7 ppm, and a DO between 20 and 50 ppm drastically decreased ARA production [36]. This indicated that excessive oxygen exposure during fermentation could impair ARA overproduction. During ARA biosynthesis, high oxygen concentrations may affect metabolism and cell growth in the filamentous mycelia, and beta-oxidation of fatty acids may be needed to obtain the extra energy required for adaptation to the high oxygen conditions."}