Alginate Production of <i>Azotobacter vinelandii</i> Using Sugar Cane Juice as the Main Carbon Source in an Airlift Bioreactor

Abstract

Bacterial alginate production has been studied to solve the uncontrollable problem of natural algae alginate composition. A challenge in using alginate in widespread applications is the high cost of equipment and operation. In this research, we aimed to optimize the conditions to produce alginate by Azotobacter vinelandii ATCC 9046 using sugar cane juice as the main carbon source. A 5-L internal circulating airlift bioreactor was designed and constructed for this research to ensure low installation and operation costs. An equivalent 60.0 mM sucrose concentration optimized for alginate production in this research was used to prepare the sugar cane juice medium for studying the effects of the nitrogen content and the pH value of the culture for alginate fermentation. The results showed that the pH-controlled value and the nitrogen concentration affected the alginate production and that the pH value of the culture affected the molecular weight of obtained alginate. A regression model was developed to predict the alginate production with a good acceptance (R2 = 81.3%). Moreover, the highest alginate production and its molecular weight obtained from the sugar cane juice medium fermented in the air lift bioreactor were as high as 7.29 ± 0.07 g L–1 and 4,735 kDa, respectively.