Eloane Malvessi

Influence of medium composition and pH on the production of polygalacturonases by Aspergillus oryzae

ABSTRACT A liquid medium containing wheat bran, salts and a source of inducer (pectin) was found to be suitable for the production of exo- and endo-polygalacturonases by Aspergillus oryzae CCT3940. Induction of polygalacturonases by purified pectin was significantly higher than when rinds of citrus fruits were used as inducer. A. oryzae growth was favoured by pH close to 4, although a drop of pH to around 3 was needed for enzymes production. Afterwards, decreasing activities were observed with the normal increase in pH to near neutrality. The highest activities were achieved with an initial pH of 4 and controlled when it decreased to a value slightly below 3 (159 units endo-PG.mL -1 at 83 h and 45 units exo-PG.mL -1 at 64 h), being the loss in polygalacturonases activities strongly reduced at this condition. The best values of pH and temperature for the action of exo-PG (4.5/57oC) and endo-PG (4.3/40oC) were assessed. Key words: Pectinase, polygalacturonase, submerged process, production medium, pH

Production and characterization of endo-polygalacturonase from Aspergillus niger in solid-state fermentation in double-surface bioreactor

Endo-polygalacturonase (endo-PG) production by Aspergillus niger T0005/007-2 in solid medium with 170 mm of height was evaluated in a cylindrical double surface bioreactor in 96-h experiments. Cell concentration close to 92 mg.g -1 dm (mg per g of dry medium) in the standard condition (static) was achieved, whereas in tests under forced aeration of 1.4 and 2.8 L.min-1. Kg-1 mm (L of air per minute per Kg of moist medium) and with the central shaft fungal biomass attained approximately 100 mg.g-1 dm. Superior endo-PG activity was obtained with the central-shaft system, 78 U.g-1 dm (units per g of dry medium). Forced aeration and pressure pulse showed no positive effect on the production of endo-PG, 45 U.g-1 dm and 28 U.g-1 dm, respectively. None of the conditions evaluated was efficient for medium temperature control. Endo-PG was stable up to 40oC. The activity decreased in 50% after 120 minutes at 50oC, which is a temperature normally found during this process.

Bioproduction and characterization of sodium, potassium, and calcium lactobionates

Lactobionic acid and its salts are substances that have several applications in the pharmaceutical area. These products were obtained by bioconversion through the enzymatic complex glucose-fructose-oxidoreductase (GFOR)/gluconolactonase (GL) present in calcium alginate immobilized cells of Zymomonas mobilis. In the reactions catalyzed by this enzyme system, the medium pH must be controlled at slightly acid values. For this purpose, NaOH, KOH, or Ca(OH)2 were used, and as a result, the respective salts were formed. The kinetic study on the formation of sodium, potassium and calcium lactobionates was followed by the steps of purification and characterization aiming the potential use of these compounds in the pharmaceutical area. In the assays for the bioproduction of sodium, potassium or calcium lactobionates, yields of 74, 77 and 84% were obtained, respectively. In the salts purification step, purity levels of approximately 95% were achieved. The structural identities of the lactobionate salts were determined by high resolution mass spectrometry, in addition to the C and H NMR analysis. The characterization demonstrates the selectivity of the enzymatic reaction of GFOR/GL of Z. mobilis, in the production of lactobionic acid and its salts.