SHORT-TERM EFFECTS OF ACETATE AND MICROAEROBIC CONDITIONS ON PHOTOSYNTHESIS AND RESPIRATION IN CHLORELLA SOROKINIANA GXNN 01 (CHLOROPHYTA)

Authors

  • Hongjin Qiao,

    1. Shandong Provincial Key Laboratory of Restoration for Marine Ecology, Shandong Marine Fisheries Research Institute, 264006 Yantai, China
      Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China
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  • Guangce Wang,

    1. Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China
      College of Marine Science and Engineering, Tianjin University of Science & Technology, 300222 Tianjin, China
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  • Kai Liu,

    1. College of Marine Science and Engineering, Tianjin University of Science & Technology, 300222 Tianjin, China
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  • Wenhui Gu

    1. Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China
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  • Received 16 March 2011. Accepted 30 March 2012.

Abstract

The culture of microalgae using organic carbon sources decreases the cost of operation in closed systems. The effect of carbon sources on microalgae is thus an interesting problem in not only theoretical research but also practical production. The short-term effects of acetate and microaerobic conditions on the growth, photosynthesis, and respiration of the green microalga Chlorella sorokiniana I. Shihira & R.W. Krauss GXNN 01 were described after acetate addition to autotrophic cultures. As the acetate concentration increased, cells needed a longer lag phase to grow, and 243.8 mM acetate completely inhibited growth. Acetate addition induced an immediate response in photosynthesis and respiration. The activity of PS II and PS I were impaired and declined with different rates, and then recovered compared with autotrophic cells. Carbonic anhydrase and Rubisco activities were also inhibited at the beginning, and respiration was increased. We propose that ATP consumption for acetate assimilation results in surplus NADPH, and then accumulated reducing power over-reduces inter-photosystem components and raises the transthylakoid proton gradient, which redistributes energy between PS I and PS II, and leads to a decrease in the PS II/PS I ratio and O2 evolution. An apparent cyclic electron flow was also observed, which may be mainly mediated by NAD(P)H dehydrogenase-dependent pathway since NADPH was in excess. These observations pointed to an acclimation process after acetate addition, and suggested the interaction between photosynthesis and respiration involving ATP and reducing power.

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