SCREENING METHOD FOR THERMOPHILIC AND HIGH GROWTH RATE METHANOL YEASTS

Abstract

To obtain thermophilic methanol-assimilating yeasts of high growth rate, soil sources collected from various regions were examined by two kinds of enrichment methods and two kinds of screening methods. Its results showed that the soil samples collected from the tropical region were rich in thermophilic yeasts. An ordinary enrichment culture using a test tube was more effective for this purpose than a continuous enrichment culture using a mini-fermentor, because many prominent yeasts were lost through the continuous enrichment culture. After the screening test of isolates by comparing the growth rate of the culture in a flask, properties of selected strains were examined, comparing them with those in continuous culture. They were divided into three types from their growth properties. Among them, the type of yeasts which grew at a low growth rate in batch culture and at high dilution rate in continuous culture was lost during screening in batch culture. Little correspondence was found between the data from the batch culture and those from the continuous culture. It would be better to omit screening by flask cultivation.