Glycolate Formation and Excretion by Chlorella pyrenoidosa and Netrium digitus

Abstract

Conditions are described whereby suspensions of Chlorella pyrenoidosa and Netrium digitus photosynthetically biosynthesize and excrete glycolate continuously in high yields. Aminooxyacetic acid, an inhibitor of pyridoxal phosphate-linked enzymes, increased the excretion of glycolate approximately 4-fold in 1 hour (8 millimolar) and 20-fold in 4 hours (40 millimolar) in the presence of 0.2% CO(2) in air. The amount of glycolate excreted in the presence of aminooxyacetate and an atmosphere of 0.2% CO(2) in air equaled or exceeded the amount excreted in 0.2% CO(2) in O(2) minus aminooxyacetate. CO(2) and light were required for glycolate excretion. Aminooxyacetate also stimulated photosynthetic glycolate excretion in an atmosphere of 0.2% CO(2) in nitrogen or helium, although the stimulation was not as great as when air or O(2) was present.The excreted glycolate was converted to H(2) and CO(2) by the combined action of glycolic oxidase and the formic hydrogenlyase complex found in Escherichia coli in total conversion yields of 80%.