Production of alginates with high viscosifying power and molecular weight by using the AT9 strain of Azotobacter vinelandii in batch cultures under different oxygen transfer conditions

Background: Alginate is a polysaccharide constituted by beta-d-mannuronic acid and alpha-l-guluronic which has several applications in the field of tissue engineering, drug delivery and other biomedical applications. This study aimed to evaluate the production, molecular weight (MW) and viscosifying power of the alginate produced by the strain AT9 cultured in a 3-L reactor, under three different oxygen transfer rates (OTR). Results: An increase in the OTRmax, in the range of 3.6-12.4 mmol L-1 h(-1) promoted cellular growth and alginate production in the cultures, reaching a specific growth rate of 0.14 h(-1) and a maximal alginate concentration of 2.9 g L-1 in cultures developed at 12.4 mmol L-1 h(-1). By contrast, at low OTR (3.6 mmol L-1 h(-1)) a maximal molecular weight of 2927 kDa was obtained and at high OTRmax (12.4 mmol L-1 h(-1)) the maximal acetylation degree (2-3%) was reached. As a result of the higher acetylation of the alginate, the viscosifying power was the highest (3.16 L g(-1)).Conclusion: Overall, our results indicate that by controlling the OTRmax it is possible to manipulate the MW, the acetylation degree and the viscosifying power of bacterial alginates produced by strain AT9. (c) 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).