Alginate molecular mass produced by Azotobacter vinelandii in response to changes of the O2 transfer rate in chemostat cultures

Abstract

Alginate production by Azotobacter vinelandii growing in chemostat cultures was evaluated under different O(2) transfer rates (OTR). As a result of modifying the culture's agitation rate from 300 to 500 rpm, the OTR increased from 9 to 15.1 mmol l(-1) h(-1) and a slight variation in the alginate production (1.7-2.2 g l(-1)) was observed. At a constant growth rate (0.1 h(-1)), the mean molecular mass of the alginate was strongly influenced by changes in the OTR, varying from 860 to 1,690 kDa. These results support a possible relationship between alginate polymerization-depolymerization process and the O(2) uptake rate.

Alginate production and alg8 gene expression by Azotobacter vinelandii in continuous cultures

“…It is clear that a change in the ISC affected the different sucrose yields and the carbon recovery. The sucrose yields on alginate (Y alg/s ) values obtained in this study were lower than those previously reported by Díaz-Barrera et al [7] in chemostat cultures, which varied between 0.26 and 0.39 g g -1 . It is possible that this difference could be attributed to the nitrogen-fixing conditions used by Díaz-Barrera et al [7], whereas in our work, the chemostat cultures were carried out under non-nitrogen-fixation conditions.…”

“…The production of alginates with specific molecular weights for biomaterials with specific applications can be achieved in a bacterial bioprocess. Studies have demonstrated that the culture conditions of agitation rate and oxygen transfer rate (OTR) affect alginate production in bioprocesses [7,15,19]. Peña et al [19] evaluated the effect of agitation rate and dissolved oxygen tension (DOT) and reported that the highest alginate production (5.0 g l -1 ) and molecular weight distribution were found at 3% DOT under a high agitation rate (700 rpm).…”

“…Peña et al [19] evaluated the effect of agitation rate and dissolved oxygen tension (DOT) and reported that the highest alginate production (5.0 g l -1 ) and molecular weight distribution were found at 3% DOT under a high agitation rate (700 rpm). In addition, it has been demonstrated that the OTR affects the molecular weight of alginate polymers in cultures of A. vinelandii at a constant specific growth rate [7]. Recently, Lozano et al [15] showed that the molecular weight of alginate produced under non-oxygen-limited conditions increased by decreasing the OTR of batch cultures of A. vinelandii.…”

Selection of Hyper Exopolysaccharide Producing and Cyst Forming Azotobacter Isolates for Better Survival under Stress Conditions

“…and Azotobacter vinelandii, respectively) can improve aggregate formation. The polysaccharides are apparently adsorbed on soil particle surfaces and cement particles together (Diaz-Barrera et al, 2009) On the other hand, it was shown previously that microbial biomass and polysaccharide production are increased in association with the stimulation of microbial populations in the rhizosphere of various plants. The factors that favor root cap polysaccharide production may be expected to improve soil adhesion to roots or root adhering soil aggregation.…”

Impact of Azotobacter exopolysaccharides on sustainable agriculture

“…The applicability of Azotobacter EPS as a thickening or gel-forming agent is strongly determined by its rheological characteristics like viscosity. Production and composition of EPS varied with several environmental factors (Diaz-Barrera et al 2009). …”