Carbon dioxide fixation to starch and following co-fermentation of ethanol and 2,3-butanediol by a marine microalga, Chlamydomonas sp YA-SH-1

Products analyses in a fermented slurry of a green alga, Chlamydomonas sp. YA-SH-1, were re-examined. By gas chromatography (GC) -mass spectometry, 2,3-butanediol was detected at a retention time of propionic acid, which we had assigned by GC [2]. Data obtained by the re-examination showed that under about 20% of starch remained in about 80 g cells carbon balance between consumed starch and products was holded with just a little over 5%; 1020 mmol of C contained in consumed starch converted to ethanol, 2,3-butanediol, acetic acid and inorganic carbon including CO2 of 420, 350, 4 and 77 mmol C, respectively. For the explanation of this carbon distribution among products, a new CO2-ethanol conversion pathway coupled with alcohol fermentations is proposed.