Fig. 1
Cultivation and ethanol production data of a Synechococcus 7002 producer line compared to WT. a Vapor–liquid equilibria (VLE) corrected ethanol production and respective calculated rate of ethanol production per day (dotted line). Trend lines represent 4th and 3rd order polynomial regressions. b Optical density at wavelength λ = 750 (OD750). Trend lines represent 2nd order polynomial regressions. c Specific chlorophyll content calculated from chlorophyll and OD750 measurements (Additional file 1). d Maximum photosynthetic rate (P max) calculated as µmol (O2) h−1 mg −1Chl of WT and the producer. Data were obtained from a representative cultivation (Additional file 1). e Carbon partitioning into ethanol (%) of the producer strain. Carbon partitioning was calculated from VLE corrected ethanol production relative to total organic carbon (TOC) in 4 cultivation intervals that span phases I–III as indicated. As TOC is calculated by subtracting measured total inorganic carbon (TIC) from measured total carbon (TC), it does not contain CO2 that is lost by enzymatic reactions, for example by pyruvate decarboxylation. Data calculated from two representative producer cultures. f Coomassie-stained SDS-PAGE of crude cell extracts (10 µg total protein, each lane) of WT and producer strain grown in parallel cultures at day 8 (at the transition from phase I to phase II) and day 22 (in the middle of phase III). Replicate 1 and 2 represent independent cultures. The ethanologenic gene cassette, consisting of Zymomonas mobilis pyruvate decarboxylase (PDC) and Synechocystis 6803 alcohol dehydrogenase (ADH), is located on the self-replicating plasmid #1449 (Additional file 9). Both proteins, the constitutively overexpressed ADH and the induced PDC are clearly present in the producer strain. Samples from the same cultures were additionally analyzed by blue-native PAGE (Additional file 10). g PDC activity in cell extracts of the ethanol producer. Data shown are averages of 4 replicates. h ADH activity in cell extracts of the ethanol producer. Data shown are averages of 4 replicates. Unless stated otherwise, data are averages ± standard deviation of 3–4 independent cultures from a 32 day batch cultivation (Additional file 1). Gray underlay indicates ethanol production phases I–III