Weak magnetic field intervention on outdoor production of oil-rich filamentous microalgae: Influence of seasonal changes.

The weak magnetic field (MF) intervention on the semi-continuous system of filamentous algae Tribonema sp. during outdoor cultivation was investigated using starch wastewater. Results show that except for winter, MF in other seasons can effectively improve the algal biomass yield and oil productivity. In summer, the biomass concentration and oil productivity of Tribonema sp. could reach up to 14.7 g/L and 0.216 g/(L d) (130 mT), which increased by 9.8% and 35.8% respectively compared with the control group without MF intervention. By continuously shortening HRT to increase the nutrient load, the removal rate of COD, total nitrogen and total phosphorus all reached more than 87.9%. MF intervention not only weakened the bacterial diversity in open-photobioreactors system but also proved to be beneficial to the establishment of bacteria-algae symbiotic system. As a non-transgenic method, MF effectively up-regulated the growth of filamentous microalgae and promoted the biosynthesis productivity of high value-added compounds.