A Study of the Esterases and Their Function in Candida lipolytica, Aspergillus niger and a Yeast-like Fungus

Summary: Esterases, determined by polyacrylamide gel electrophoresis, were present when Candida lipolytica was grown in a liquid, shaken, glucose-mineral salts medium. Intracellular esterase activity increased during growth, but extracellular esterase activity was small and increased only marginally. Esterases were not detected in organisms grown on solid glucose-mineral salts medium, but were present when glycerol tributyrin replaced glucose. At the onset of asexual sporulation in a yeast-like fungus, three new esterases occurred. Intracellular esterase activity increased, intracellular lipid utilization occurred, and the respiratory quotient decreased. No extracellular esterase activity was detected. Esterases were only detected in Aspergillus niger at late stages of conidia-tion when intracellular lipid decreased. Esterase activity was not detected in the mitochondria or in the cell-free growth medium. Esterases of all organisms tested hydrolysed glycerol tributyrin and were arbitrarily classified as lipases; intracellular lipid decreased with increase in esterase activity function. Esterase and profile changes may reflect a role of lipids in sporulation and physiological ageing.