Metabolic activities and dynamic aspects of growth in Geotrichum candidum

Abstract

The metabolic activity of Geotrichum candidum was investigated. The chromatographic analysis of the cell pool and of the acid hydrolysate revealed the presence of almost all the amino acids previously detected in other yeasts. The pool pattern was not greatly different from the acid hydrolysate pattern, but i t varied in certain stages of growth.Little information is available concerning the metabolic activity of G. candidum. Our previous report (OSMAN et al, 1973) showed that Q. candidum, isolated from a local source, is a promising new protein producer. The yeast was grown in the previously formulated synthetic medium (OSMAN et al. 1973).The advantage of using a synthetic medium was to avoid possible incorporation of preformed biological compounds into the yeast. Therefore, the occurrence of any metabolite is taken as an ability to synthesize that compound.Material and methods G . candidum isolated from decaying fruits in Egypt was maintained and cultured after OSMAN et al. (1973). Metabolites were determined by the methods adopted by OSMAN and CHENOUDA (1965a). Amino acid pools and acid hydrolysates of the dried cells were qualitatively and quantitatively determined after OSMAN and CHENOUDA (1965b) and MARKH and YURCHENKO (1965) using a DDR extinction recorder. Results and discussion T i m e c o u r s e of p r o t e i n s y n t h e s i s i n r e l a t i o n t o t h e m e t a b o l i c a c t i v i t i e s of G. candidurnThe highest yield of biomass on the 7th day corresponds to the consumption of sucrose and nitrogen in the medium and the synthesis of protein and lipids. The total carbohydrate content of the yeast cells did not change significantly during the fermentation period. The noticeable drop in the p H may be ascribed to the progressive formation of keto acids (Table 1).Chromatographic analysis revealed that a-ketoglutaric and pyruvic acids were the only keto acids detected in the cell pool and the culture medium of G. candidum. The progressive decrease of the keto acid pool may be due to their incorporation in metabolic processes and excretion into the culture medium. I n contrast to the low level of pyruvate in the cell pool, this compound was found in large amounts in the culture medium. This may be either due t o the high permeability of yeast cells to pyruvate or t o its transient metabolic production. The presence of the keto acids may indicate the functioning of the tricarboxylic acid cycle in G. candidum.