선정균을 장기간 보다 안전하게 관리하고 균의 성질을 개선하기 위하여 실험한 결과는 다음과 같다. 1) 선정균은 대체로 0~5$^{circ}C$에서 soil 배지에 보존하는 것이 좋았으며 보존기간 10개월까지는 산생성력에 큰 변화를 보이지 않았다. 2) 선정균 M-315는 강산성지에 계대배양하므로서 산생성능이 약간 향상되였으며 종균으로는 포자형성배지에 7~10일간 배양한 균의 포자로 접종하는 것이 좋았다. 3) 선정균에 자외선을 조사시킨 결과 형태적으로 변화된 변이주 109주을 분리하였고 그 중 산생성력이 3.2% 향상된 변이주 M-812를 얻었다.
These experiments were conducted to manage more safe the selected strains and improve their characteristics. The results obtained were as follows: Preservation on soil at the range of 0 to 5 C was suitable and there were no remarkable changes on their abilities to produce citric acid until 10 months preservation. The successive transfer of spore slightly stimulated the selected strain, M-315 to produce citric acid and the spore precultured on sporulation medium for 7-10 days was desirable as inoculum. Under UV-irradiation from the selected strains, 109 mutants whose morphological characteristics were changed were isolated. Among them, the mutant M-80-12 was shown 3.2％ increase on acid producing ability than that of its parent.
