Bioeffects Of Microwave On Nannochloropsis Oceanica And Its Mechanism

Nannochloropsis is a. marine unicellular alga. It has many nutritional components such as carbohydrate, proteins, amino acids, polyunsaturated fatty acids (PUFA) et al, especially it produces eicosapentaenoic acid (EPA) at high level. So it has high research value. In this paper we selected the alga strain of Nannochloropsis as the material of experiments, optimized the medium and culture conditions, investigated the effect of microwave radiation on the growth of Nannochloropsis. Bioeffects were explored by detecting varieties of the antioxidant system, cell membrane function, photosynthesis pigments and chemical structure. The main results are as follows:Nannochloropsis Q-2 was selected among Z-1, Q-2 and S-3 because of its high growth rate and high content of total fatty acids, EPA and PUFA.Optimum MAV medium was as follows: 1mL MAV solution was added to 1L seawater: (l)MAV solution (g/L): KNO₃ 140, KH₂PO₄ 10, FeSO₄ 2.5, Na₂EDTA 20, MnSO₄ 0.40, vitamin B₁₂ 5×10^-6, vitamin B₁ 6×10^-3; (2) artificial sea water (g/L): NaCl 5, MgSO₄ 3.5, MgCl₂ 2.5, CaCl₂ 1.2, KCl 0.8, NaHCO₃ 0.2. Optimum culture conditions were as follows:inoculation density was 9×10⁵ cells/mL, the loaded quantum of 500mL flask was 50mL, illumination intensity was 8000 lx and pH range was pH 6.0～pH 8.5.The optimum treatment power and time of microwave were 162W and 12S. The effect of microwave on the alga was most significant when radiated twice and at early log phase whose cell density was 1.8× 10⁷ cells/mL. It increased cell density and growth rate by 16.5% and 8.0% respectively. But in our experiment the effect of microwave on the growth of alga could not inherit stably.For antioxidant system, the total antioxidant ability and anti-hydroxyl free radical ability declined by 115.4% and 26.6% respectively; The anti-superoxide anion ability, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX) and the content of glutathione (GSH) and carotenoid (CAR) increased by 21.2%, 20.6%, 55.5%, 27.1%, 7.6% and 25.0% respectively.For cell membrane function, maleic dialdehyde (MDA) content, activities of Na⁺K⁺-ATPase, Ca²⁺Mg²⁺-ATPase and electrolyte infiltration rate increased by 10.7%,...