RELATIONSHIP BETWEEN MORPHOLOGY, RHEOLOGY AND GLUCOAMYLASE PRODUCTION BY Aspergillus awamori IN SUBMERGED CULTURES

Abstract

The influence of inoculum preparation on Aspergillus awamori morphology, broth rheology and glucoamylase synthesis in submerged cultures was investigated. A series of runs were performed in fermenters, using initial total reducing sugar concentrations of 20 g/L and 80 g/L. The inocula were prepared in a rotary shaker, at 35oC and 200 rev/min, using a spore concentration of 9.2 x 105 spores/mL and varying both cultivation time and medium pH during the spore germination step. Three types of inocula were used: inoculum cultivated for 24 hours at an initial pH of 5.0, and inocula cultivated for 7 hours at both a pH of 2.5 and a pH of 5.5. Regarding glucoamylase production, the inoculum which provided the best results was shaker cultivated for 7 hours at a pH of 2.5. This inoculum produced glucoamylase of about 1,221 U/L in the fermenter, which was between 20% and 30% higher than those obtained using other inocula.