Production of Alginate by Azotobacter vinelandii in semi-industrial scale using batch and fed-batch cultivation systems

Abstract

The alginate production by Azotobacter vinelandii in batch and fed-batch culture was studied in semi-industrial scale level using 16-L and 150-L stirred tank bioreactor (STR). During batch cultivation in 16-L STR, the maximal volumetric alginate production of 0.98 g/L was obtained in uncontrolled pH culture, whereas, the maximal specific alginate production of 0.15 g alginate/g cells was obtained in controlled pH culture. As glucose was found to be the limiting substrate in this process, fed-batch cultivation was developed using C-source constant feeding strategy in combination with other key medium components to improve volumetric alginate production. The maximal volumetric and specific alginate productions were 7 g/L and 0.45 g/g, respectively, in fed-batch culture. Based on these data, the production process was scaled up using constant power input (P/V) criteria to 150-L stirred tank bioreactor. Bioprocess scaling up using this strategy improved further the volumetric alginate production up to 20 g/L concomitant with increased specific alginate production reaching 0.65 g/g after 48 h cultivation.