tailieunhanh - Yamanaka et al. AMB Express 2011, 1:24 http://www.amb-express.com/content/1/1/24 ORIGINAL Open

Yamanaka et al. AMB Express 2011, 1:24 ORIGINAL Open Access Reduction of exogenous ketones depends upon NADPH generated photosynthetically in cells of the cyanobacterium Synechococcus PCC 7942 Rio Yamanaka1*, Kaoru Nakamura2 and Akio Murakami3 Abstract Effective utilization of photosynthetic microorganisms as potential biocatalysts is favorable for the production of useful biomaterials and the reduction of atmospheric CO2. For example, biocatalytic transformations are used in the synthesis of optically active alcohols. We previously found that ketone reduction in cells of the cyanobacterium Synechococcus PCC 7942 is highly enantioselective and remarkably enhanced under light illumination. In this study, the mechanism of lightenhanced ketone reduction was investigated. | o AMB Express a SpringerOpen Journal Yamanaka et al. AMB Express 2011 1 24 http content 1 1 24 ORIGINAL Open Access Reduction of exogenous ketones depends upon NADPH generated photosynthetically in cells of the cyanobacterium Synechococcus PCC 7942 Rio Yamanaka 1 Kaoru Nakamura2 and Akio Murakami3 Abstract Effective utilization of photosynthetic microorganisms as potential biocatalysts is favorable for the production of useful biomaterials and the reduction of atmospheric CO2. For example biocatalytic transformations are used in the synthesis of optically active alcohols. We previously found that ketone reduction in cells of the cyanobacterium Synechococcus PCC 7942 is highly enantioselective and remarkably enhanced under light illumination. In this study the mechanism of light-enhanced ketone reduction was investigated in detail using several inhibitors of photosynthetic electron transport and of enzymes of the Calvin cycle. It is demonstrated that light intensity and photosynthesis inhibitors significantly affect the ketone reduction activity in Synechococcus. This indicates that the reduction correlates well with photosynthetic activity. Moreover ketone reduction in Synechococcus specifically depends upon NADPH and not NADH. These results also suggest that cyanobacteria have the potential to be utilized as biocatalytic systems for direct usage of light energy in various applications such as syntheses of useful compounds and remediation of environmental pollutants. Keywords biocatalysis cyanobacteria ketone reduction light energy NADPH photosynthesis Introduction Most chlorophyll-containing organisms are photoauto-trophic and manufacture various organic compounds from inorganic carbon in the form of CO2 using solar light energy. All other organisms except for chemosynthetic bacteria are heterotrophic and ultimately depend upon photoautotrophic organisms to provide their energy and nutrients Anemaet et al. 2010 . Oxygen-evolving .