The thermophilic bacterium, Geobacillus thermantarcticus, (DSM 9572) strain M1, isolated from geothermal soil, near the crater of Mount Melbourne (74° 22’ S, 164° 40’ E) in Antarctica, was screened for its capacity to produce enzymes with thermostable enzymatic activities. This microorganism produces an extracellular xylanase, β-xylosidase, an intracellular xylose/glucose isomerase and protease. Moreover, Geobacillus thermantarcticus produces two exocellular polysaccharides (called EPS 1, EPS 2) that give a typical mucous character to colonies. The exopolysaccharidic fraction was produced with all single carbon substrate assayed, although a higher yield of 400 mg/L was obtained with mannose used as sole carbon and energy source. NMR spectra confirmed that EPS 1 was a heteropolysaccharide where the repeating unit was constituted by four different α-D-mannoses and three different β-D-glucose residues. It seems to be close to some xanthan polymers. EPS 2 was a mannan: four different α-D-mannoses were found as the repeating unit. The scale-up of the batch process and the development of a fed-batch strategy to further improve polysaccharide production were performed, reaching an EPS yield of 3g/L.
View Full Article