SELECTION OF ANTIBIOTIC-RESISTANT MUTANTS WITH ENHANCED ISOAMYLASE ACTIVITY IN PSEUDOMONAS-AMYLODERAMOSA

Isoamylase-hyperproducing strains of Pseudomonas amyloderamosa were br ed by mutagenesis with UV light and N-methyl-N'-nitro-N-nitrosoguanidi ne (NTG). The selection criterion for such strains was based on the fo rmation of large turbid zones around the bacterial colonies in agar me dium containing antibiotics and 1% waxy corn starch. Mutant WN6410 was obtained by treating P. amyloderamosa JD210 with five cycles of 1 x 1 0(4) muJ UV light and one cycle of NTG. P. amyloderamosa WN6410 had 22 -fold increase in isoamylase activity when compared to wild-type strai n SB15 and the maximal enzyme activity, 5,100 U/ml, could be achieved within 48 h in 2.5 L fed-batch fermentation.