Applications of image analysis in the characterization of Streptomyces olindensis in submerged culture

The morphology of Streptomyces olindensis (producer of retamycin, an antitumor antibiotic) grown in submerged culture was assessed by image analysis. The morphology was differentiated into four classes: pellets, clumps (or entangled filaments), branched and unbranched free filaments. Four morphological parameters were initially considered (area, convex area, perimeter, and convex perimeter) but only two parameters (perimeter and convex perimeter) were chosen to automatically classify the cells into the four morphological classes, using histogram analysis. Each morphological class was evaluated during growth c arried out in liquid media in fermenter or shaker. It was found that pellets and clumps dominated in early growth stages in fermenter (due to the inoculum coming from a shaker cultivation) and that during cultivation, the breakage of pellets and clumps caused an increase in the percentage of free filaments. The criteria of morphological classification by image analysis proposed were useful to quantify the percentage of each morphological class during fermentations and may help to establish correlations between antibiotic production and microorganism morphology.

Influence of spore concentration on microorganism morphology and on glucoamylase production in submerged cultures of Aspergillus awamori

The influence of the spore concentration in the inoculum preparation on microorganism morphology and glucoamylase synthesis by submerged cultures of Aspergillus awamori was investigated. A series of fermenter runs were perfomed, using an initial total reducing sugar concentration of 40 g/L. The inocula were prepared in a rotatory shaker, at 35§C 200 rev/min for 24 hours, varying spore concentration in the flasks from 9.5 x 10(3) to 1.8 x 10 (7) spores/mL. The inocula prepared with a spore concentration between 9.5 x 10(3) spores/mL and 5.0 x 10(6) spores/mL were composed by a cell suspension mainly in the pellet form, which led to a filamentous growth in the fermenter. Glucoamylase production was not affected by this range of spore concentration, reaching values between 2,100 U/L and 2,300 U/L. However, a higher spore concentration in the inoculum preparation (1.8 x 10(7) spores/mL) led to a inoculum formed by a cell suspension in the filamentous form containing many spore agglomerates (non-germinated spores). The kind of inoculum led to a growth predominantly in the pellet form in fermenter, which reduced the glucoamylase production in 30 (per cent).