Abstract
Two strains of Saccharomycopsis guttulata, JB-1 and JB-3, isolated from stomach contents of domestic rabbits, were grown under different gas phases, and their growth rates were compared. Strain JB-1 grew exponentially at a maximal growth rate under a continuous gas phase of 15% CO(2), 2% O(2) in nitrogen. High cell yields with low cell granulation were obtained. The growth rates were almost the same between oxygen concentrations of 0.25 and 20% at 15% CO(2). Poor growth and early cell granulation occurred in the absence of oxygen at 15% CO(2). Growth increased at 2% O(2) in direct proportion to the carbon dioxide concentration up to 10 to 15% CO(2). A very high carbon dioxide content (e.g. 98%) was somewhat inhibitory. Cell granulation always occurred during the maximal stationary phase in media at pH 4, but was relatively slight at pH 5.6 or higher. Strain JB-3 responded to various gas phases in a similar manner except that it grew slowly in the absence of oxygen at 15% CO(2) (pH 4). The effect of an optimal gas phase on the growth of strain JB-1 was examined in relation to other environmental conditions. In the presence of 15% CO(2), 2% O(2), this strain grew exponentially in yeast autolysate-Proteose Peptone-glucose medium at 37 C at pH 2, 4, and 5.6 at approximately the same rate; the growth rate was somewhat lower at pH 6.2. Under similar conditions, strain JB-1 grew at 30 C and pH 4 at one-sixth its maximal growth rate. Cell granulation was greatly reduced at this temperature. With adequate CO(2) strain JB-1 also grew at a reduced rate in a yeast autolysate medium previously reported not to support growth. Results indicate that continuous gassing with an optimal gas phase increases the growth rate to the extent that the growth rate surpasses the death rate by a significant margin; as a result, granulated cells can be avoided almost entirely in the log phase.