Studies on Scenedesmus acutus growth II. Effect of autotrophic and mixotrophic growth on the amino acid and the carbohydrate composition of Scenedesmus acutus

As a general rule an increase in carbohydrates occurs during the light phase of the cell cycle and that of protein during phase, although variations were found in these components under autotrophic and mixotrophic growth conditions. The results are based on the quantitative determination of carvohydrates as trimethylsilyl (TMS) derivatives and amino acids as N-trifluoroacetyl-n-butyl (TAB) esters in algal cells cultured in light and dark periods by gas-liquid chromatography (LC). Cells harvested during the dark period contained more amino acids as compared to similar cultures harvested during the light phase. In light, the production of amino acids of the aspartate family increased in cells cultivated with glucose and carbon dioxide. With glucose as sole carbon source, the carbohydrate content was higher in the dark than in the light period. Under continuous light conditions, in the presence of carbon dioxide, there was a decrease in the carbohydrate content also. Gas-liquid chromatography analysis of the extract of the purified cell walls showed that they are made up of 0.076% carbohydrates and 0.28% amino acids on the dry weight (DW) basis of whole cells. The results on the metabolism of cells, under autotrophic and mixotrophic conditions, are discussed in this article.