{'fraction_non_alphanumeric': 0.01856763925729443, 'fraction_numerical': 0.014588859416445624, 'mean_word_length': 5.565217391304348, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Ribostamycin production by a mutant of butirosin producing bacteria.

By the use of our improved colony selection technique, xylostasin and ribostamycin producing mutants were isolated from nitrosoguanidine treated Bacillus circulans B15M, a producer of butirosins A and B. Among these structurally related aminoglycosides, ribostamycin is the well-known product of a Steptomyces and has not been isolated as a bacterial metabolite. A selected mutant of strain 306, which produces xylostasin and ribostamycin, was futher mutagenized in expectation of getting an improved strain having the ability to accumulate a large amount of ribostamycin in the culture broth. One mutant, strain 451, derived from strain 306, produced ribostamycin free of xylostasin.