Fermentative prodn. of gluconic acid from aq. sugar contg. liq. - using new strains of Aureobasidium pullulans, used as preservative and cement additive

摘要

Prodn. of gluconic acid (GA) is effected by fermenting an aq. sugar-contg. liq. with an Aureobasidium pullulans strain capable of converting glucose to GA in continuous culture, giving at least 200 g/l GA with a conversion of at least 90% and a molar selectivity of at least 90%. Fermentation is effected at 24-32 deg.C. and pH 4.5-8 in a medium with an N-dependent Fe or Mn ion concn., which is at least 0.5 mM at an N content corresp. to 3g/l NH4Cl. Also claimed are A pullulans strains which are: (a) isolated from field and forest flowers by culturing under acidic conditions with an elevated glucose concn. and a good O2 supply; (b) isolated from cultures produced by incubating comminuted flowers and stalks of middle-European forest and meadow flowers (collected in spring to summer) in a citric acid soln. with a pH of 2.5 contg. 100g/l glucose and a wetting agent, with an abundant O2 supply provided by shaking; or (c) selected from strains DSM 7085-7088. Pref. fermentation is effected continuously at 29-31 deg.C. and pH 6-7 with a residence time of 10-40 hr. using non-immobilised microorganisms with biomass retention, or using immobilised microorganisms in a fluidised-bed fermenter. The supply medium contains at lest 0.7 g/l KH2PO4 and has N-dependent Fe, Mn and Mg concns. which are 0.5-3, 2.5-5 and 1-2mM respectively at an N content corresp. to 3g/l NH4Cl. The glucose concn. is 300-600 g/l. USE/ADVANTAGE - Ga and its salt are used for cleaning purposes, in the pharmaceutical, good and drinks industries, esp. as preservatives, and as cement additives. The new strains have good osmotolerance and give high GA yields (see above) under continuous fermentation conditions.