Glycolate biosynthesis by Scenedesmus and Chlorella in the presence or absence of NaHCO3

Abstract

Both Scenedesmus and Chlorella excreted comparable quantities of glycolate. Glycolate formation was dependent upon light and oxygen, but occured in the absence of added CO2 or NaHCO3 for net photosynthesis. In an environment of 3000 ft. c. light and an atmosphere of oxygen, about 35 μg glycolate were excreted per hour per milliliter 1% (v/v) algae without NaHCO3 or CO2. Upon addition of NaHCO3 the rate increased to about 55 μg. Glycolate formation in the light in the absence of CO2 may result from photometabolism of algal polysaccharides.Glycolate excretion by Scenedesmus occurred at all pH values between 6.5 and 9.5 and was not related to utilization of bicarbonate. Scenedesmus obliquus excreted glycolate when existing in plates of four or eight cells, but not when present as small individual cells.At pH 9 (14)C fixation by Scenedesmus was faster than fixation by Chlorella. There was no significant difference in products of (14)C fixation formed by Scenedesmus at pH values between 6.5 and 9.5.For unknown reasons α-hydroxy-2-pyridinemethanesulfonate stimulated CO2 fixation by Scenedesmus by at least 100%. This sulfonate had no effect on glycolate excretion nor upon the distribution of (14)C among the products of (14)CO2 fixation by Scenedesmus.