The Metabolism of Chlorella

Abstract

These tests were carried out using the following species of Chlorella: C. variegatus, viscosa, vulgaris var. genevensis, rubescens, luteo-viridis, together with one specie not recognized. In addition Chlorococcus humicola and Mannochloris bacillaris were included within the series.

The base medium was Knopf's solution diluted 3 times with distilled water. When needed, it was rendered semisolid by 1.5% agar.

Nitrates are reduced to nitrites by 3 of these strains, C. sp?, C. vulgaris, and C. rubescens as indicated both by sulphanilic acid and by starch iodide. This reaction is slow but was definite in one month. On the other hand nitrite is oxidized to nitrate by C. luteo-viridis as proven by diphenylamine and again the test period was 30 days. Gelatine is liquefied very slowly by C. rubescens. Certain split products of protein are favorable to increased growth since peptone in amounts varying between 0.1% and 0.7% increase the growth of C. vulgaris, C. rubescens, and C. luteo-viridis. Urea in concentrations of 0.1% and 0.02% inhibits the growth of these 3 stains partially also, while ammonium carbonate in similar concentration was unfavorable to C. rubescens and C. luteo-viridis but stimulated slightly the growth of C. vulgaris.

A series of tests was made to determine the influence of amino acids upon the growth of these algae. This group of compounds included glutamic acid, valine, arginine, leucine, d- 1- alanine, phenylalanine, histidine, aspartic acid, serin, tryptophane, glycine, tyrosine, cystine and cysteine. Isoelectric gelatine also was tested here. In comparison to controls, leucine increased the growth of C. variegatus, Chlorococcus humicola, M. bacillaris, C. sp.?, and C. rubescens. Glycine stimulated all of these algae as also did tyrosine, with the exception of C. sp?. Arginine aids proliferation of each alga with the exception of M. bacillaris. Alanine was beneficial to all but Chlorococcus humicola and C. luteo-viridis. Valin and serin were beneficial to all except Chlorococcus humicola. Phenylalanine stimulated C. variegatus and C. rubescens but in varying degree depressed the other cultures.