GENERAL PROPERTIES OF BIOTIN UPTAKE SYSTEM IN LIPOMYCES STARKEYI

Abstract

The properties of the biotin uptake system of Lipomyces starkeyi IAM 4753 were investigated in proliferating and nonproliferating cells from the standpoint of explaining the characteristics of the biotin-requiring property of the organism in a medium with a pH from 5.5 to 6.5. The rate of biotin uptake was linear with time for at least the first 6hr. Uptake of ^14C-biotin showed the system to be an aeration- and energy source-dependent process. This was confirmed by the almost complete inhibition of biotin uptake with 1mM of 2, 4-dinitrophenol, potassium cyanide, and sodium azide.
Biotin uptake is pH-dependent, and the optimum condition for uptake is a pH of 4.2. Biotin uptake is operative between a pH of 5.5 and 6.5, and thus L. starkeyi IAM 4753 can grow in a medium with a pH from 5.5 to 6.5, when biotin is supplemented. The uptake of biotin by the cells is influenced by the biotin concentration in the medium employed. The greatest uptake was observed when the cells were grown in a minimal medium without any supplementation of biotin.
Apparent activity for biotin uptake per mg dry cell was considerably influenced by culture age. The amount of ¹⁴C-biotin taken up by mg dry cell harvested during the logarithmic phase was the highest, decreasing gradually as the growth phase proceeded.