Study On Functional Mechanism Of Promoting The Growth And Enhancing H₂ Photoproduction In Chlamydomonas Reinhardtii By Sodium Sulfite

Chemical industry production and the burning of fossil fuels release a large amount of SO2 and its main by-product sulfite,causing great harm to the environment.The use of microalgae to assimilate sulfur-containing wastes from industrial production and to promote the generation of biomass,such as hydrogen,is conducive to protecting the environment and turning waste into treasure.However,there are few studies on the effective use of sulfites in microalgae.In this paper,we have explored Chlamydomonas reinhardtii（C.reinhardtii）,which is a dominant species of photosynthetic hydrogen,had efficiently utilization Na₂SO₃ as a solo sulfur source,and greatly promoted the hydrogen production.The main results are as follows:（1）C.reinhardtii can efficiently use Na₂SO₃ as a solo sulfur source,in the context of sulfur deficiency,adding 1～20 mM Na₂SO₃ to culture C.reinhardtii will not produce significant inhibition,suggesting that the C.reinhardtii can tolerate high concentrations of sulfite.Most importantly,treatment with appropriate concentration of Na₂SO₃ can promote the growth of sulfur deficiency cells.（2）Adding 10 mM Na₂SO₃ under natural conditions could enhance the hydrogen production of C.reinhardtii by about 160 times.We further found that.Na₂SO₃ is able to remove O2 molecules in intact cells of C.reinhardtii via the reaction of sulfite with O2 produced at the acceptor side of PSI to generate sulfate,and thus stimulate the expression of hydrogenase to enhance the yield of H2 photoproduction.（3）By using Na₂SO₃.light intensity plays an important role and acts as a control switch in regulating C.reinhardtii growth and hydrogen production.That is,in the high light,Na₂SO₃ mainly promote the photosynthetic hydrogen,while in the growth light,Na₂SO₃ mainly promote the growth.In summery,C.reinhardtii can use sulfite as a sulfur source,treatment with appropriate concentration of Na₂SO₃ can promote the growth of sulfur deficiency cells.The synthetic biomass can be used for hydrogen production.For the first time we have found that sodium sulfite is most likely to reduce the oxygen content and to increase the hydrogen content by photooxidation.Light intensity plays a key role in regulating the growth and photosynthetic hydrogen production of C.reinhardtii.This study provides an example and theoretical basis for the use of wastes sulfur compounds in microalgae for "turning waste into treasure".