Abstract: In the production of plasminogen activator from animal cells in a nutrient solution, the addition of a large amount of fumaric acid, malic acid, succinic acid, and/or glycolic acid to the nutrient solution brings about a 30 to 180% increase in the amount of plasminogen activator produced.

Abstract: A plasminogen activator having a molecular weight of 45,000 to 68,000 is formed as a single fraction in the cells of human kidney or lung, and is separated and recovered with good efficiency without reducing its molecular weight. The pH of a solution to be contacted with said cells and the concentration of dissolved oxygen should be maintained within suitable ranges in order to form the plasminogen activator having a molecular weight of 45,000 to 68,000 as a single fraction. Furthermore, by properly adjusting the residence time of the solution with the cells, the activator can be formed over a long period of more than 40 days. To separate the activator, the pH of the solution in the separating step is maintained preferably at 4 to 12. By causing a metal chelating agent to be present in the solution in the separating step, the plasminogen activator can be obtained without reducing its molecular weight.

Abstract: An antibiotic designated as No. K-73A, which is produced by cultivating a strain of Streptomyces tanashiensis K-73, and then isolating and recovering the antibiotic from the cultured broth thereof.