Conidia of certain penicillin producing Penicillium chrysogenum industrial strains produced polyfructose.Two types of polyfructoses were formed by conidia of P. chrysogenum B10 from sucrose and with less yield from raffinose.Ten percent of the fructans were in water insoluble form attached to the outer wall of conidia.The other, ethanol-precipitable fructan formed a colloid opalescent solutionThe latter had inulin type β (2 → 1) bonds, identified by 13C NMR spectroscopy, between fructose mols. and had a mol. weight of 217,000 daltons.The KM value of sucrose hydrolysis, the first step of inulin production, was 0.86 m.The invertase hydrolyzed about 70% of the sucrose on the second day.Optimal conditions for inulin formation were: pH 6.0, 25-45 °C, 100 mg/mL sucrose, 107 spore/mL.The maximum conversion rate of fructose from sucrose into precipitable inulin was about 10% after 48 h incubation.The inulin production could be inhibited by glucose.