Abstract: Improved pullulanase yields are achieved by incubating culture mediums containing pullulanase producing mutants of the Klebsiella genus. The mutants generally produce approximately equivalent amounts of extracellular and superficially bound pullulanase in an easily recoverable and usable form. Optimum pullulanase production is achieved when amylopectin is used as the sole carbohydrate source. Conventional pullulanase inducers such as maltose, maltotriose and/or pullulan repress the mutant strains capacity to produce pullulanase. The mutants are capable of elaborating pullulanase in a culture media containing dextrose as the sole carbohydrate source.