The Heterotrophic Nutrition of Chlorella vulgaris (Brannon No. 1 Strain): With two Figures In the Text

Abstract

A range of sugars, sugar alcohols, sugar phosphates, organic acids, and monohydric alcohols have been tested as carbon sources for growth and as respiratory substrates using Chlorella vulgaris, Brannon I, grown in darkness. Much higher rates of growth and respiration were obtained with d-glucose than with any other substance tested. Ethanol (at 0·005 M.) sustained both growth and respiration at c. 50 per cent, of the level with glucose (0·028 M. or higher). Evidence was obtained that the organism can become ‘adapted’ to utilize d-galactose and sucrose as effective carbon sources. Sustained growth was not obtained with any of the other substances tested. The glucose monophosphates, methanol and certain organic acids (oxalacetate, α-ketoglutarate, cis-aconitate, and pyruvate) clearly stimulated oxygen uptake but to a less extent than ethanol. The other substances tested were either inhibitory to respiration or inactive or of very low activity as substrates. The growth in darkness and in liquid culture of Chlorella when supplied with d-glucose was insensitive to pH over the range 4·5 to 7·0 and was markedly enhanced by a high level of aeration. Gains in cellular dry weight ranging from 45 to 90 per cent, of the weight of d-glucose disappearing from the culture medium were recorded in growth experiments; measurements of CO2 evolution in the Warburg indicated retention of up to two-thirds of the glucose-C in cell material.