Fan Jianhua, Zheng Lvhong
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China.
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China.
J Biosci Bioeng. 2017 Sep;124(3):302-308. doi: 10.1016/j.jbiosc.2017.04.009. Epub 2017 May 5.
Salt stress has been proven very effective in enhancing the lipid content among many photoautotrophically grown microalgae species including marine and freshwater algae. Nevertheless, its effect on heterotrophic grown cells and lipid accumulation is scarcely known. This study sought to demonstrate a new train of thought for cost-effective biofuels production by heterotrophic culture of Chlamydomonas reinhardtii coupling with subsequent salt and light stress. NaCl treatments (25-200 mM) gradually suppressed the cell growth. After one day's acclimation, the cells restored slow growth with light supplement (200 μmol/m2/s) in low salt concentration (0-50 mM). However, high concentration of NaCl (200 mM) dose caused permanent damage, with over 47% cells death after 3 days treatment. The highest lipid content of 35.8% and lipid productivity of 28.6 mg/L/d were achieved by 50 mM NaCl stress and light treatment upon heterotrophic grown cells. Cells lost their green pigmentation and became yellowish under 100-200 mM NaCl conditions, whereas cells grown in 0-50 mM NaCl retained their dark-green pigmentation. Variable-to-maximum fluorescence ratio (Fv/Fm) and non-photochemical quenching (NPQ) value were markedly influenced under salt and light stress, indicating that severe inhibition of photosynthetic ability was occurred. Moreover, we further demonstrated the dynamic changes of cell growth and lipid accumulation would potentially be caused by the increase of intracellular redox state. To our knowledge, this study is the first instance in which C. reinhardtii was applied to oil accumulation by using combination of heterotrophic culture and multiple stress, and opened up a new territory for the further development of microalgae-based biofuels production.
盐胁迫已被证明在提高许多光合自养生长的微藻物种（包括海洋和淡水藻类）的脂质含量方面非常有效。然而，其对异养生长细胞和脂质积累的影响却鲜为人知。本研究旨在通过莱茵衣藻的异养培养并结合随后的盐胁迫和光照胁迫，为具有成本效益的生物燃料生产展示一种新的思路。NaCl处理（25 - 200 mM）逐渐抑制细胞生长。经过一天的适应后，在低盐浓度（0 - 50 mM）下补充光照（200 μmol/m²/s），细胞恢复缓慢生长。然而，高浓度的NaCl（200 mM）确实会造成永久性损伤，处理3天后细胞死亡率超过47%。在异养生长的细胞上施加50 mM NaCl胁迫和光照处理，脂质含量最高可达35.8%，脂质生产率为28.6 mg/L/d。在100 - 200 mM NaCl条件下，细胞失去绿色色素沉着，变为淡黄色，而在0 - 50 mM NaCl中生长的细胞保留深绿色色素沉着。在盐胁迫和光照胁迫下，可变荧光与最大荧光比值（Fv/Fm）和非光化学猝灭（NPQ）值受到显著影响，表明光合能力受到严重抑制。此外，我们进一步证明细胞生长和脂质积累的动态变化可能是由细胞内氧化还原状态的增加引起的。据我们所知，本研究是首次将莱茵衣藻应用于通过异养培养和多重胁迫相结合来积累油脂，为基于微藻的生物燃料生产的进一步发展开辟了新领域。
