莱茵衣藻黑暗厌氧发酵生产乙醇的研究

Ethanol production by dark anaerobic fermentation over Chlamydomonas reinhardtii

为了生产第三代乙醇,通过限制营养、提高淀粉含量的微藻直接发酵生产乙醇是一种值得探索的方法。采用双因素设计考察莱茵衣藻在不同初始氮源和铁源下培养积累淀粉的情况。在最佳条件下培养莱茵衣藻,藻细胞干重达到1. 9 g/L左右,胞内淀粉积累达到35. 5%左右,经黑暗厌氧诱导,胞内淀粉在30 h内降解生产乙醇。在pH为7. 5的0. 067 mol/L磷酸钠-磷酸钾缓冲液中黑暗厌氧发酵效果最佳,产率为0. 250 g/g。研究表明,当氮源缺乏时微藻会积累淀粉,但细胞生长远不如充足氮源时;含淀粉微藻在黑暗厌氧环境下能自发酵生产出一定的乙醇。因此,提出微藻三段法生产乙醇,即微藻细胞生长、淀粉积累和厌氧发酵,该微藻直接生产乙醇的过程简单可行。

It is a valuable way to produce the third generation ethanol by direct fermentation through microalgae whose starch content is increased by nutrient limitation. A dual-factor design is used to evaluate starch accumulation within Chlamydomonas reinhardtii under different initial concentrations of nitrogen and iron sources.As Chlamydomonas reinhardtii is cultured under the optimum conditions,dry weight of algae cell can reach around 1. 9 g·L-1 and starch accumulation in algae cell reaches about 35. 5%.Under dark anaerobic conditions,starch in algae cell can degrade into ethanol in 30 h. The optimal fermentation effect can be achieved in a pH = 7. 5,0. 067 mol·L-1 sodium phosphatepotassium phosphate buffer solution,with a yield ethanol of 0. 25 g·g-1. If nitrogen is short,cellular starch can be accumulated but cell growth is much slower than that observed with rich nitrogen medium.Under dark aerobic conditions,starch-containing microalgae can self-ferment to produce ethanol.A three-stage microalgae to ethanol method is proposed,including cultivation stage with nitrogen supplemented medium,starch accumulation in nitrogen-free medium and anaerobic fermentation in the dark,which is simple and feasible.