Medium Optimization of Fermentation for Enhanced Dextran Production from Weissella confusa Cab3 by Statistical Methods

Dextrans are a class of polysaccharides of varying structure with contiguous α(1-6) glycosidic linkages in the main chain and varying percentage of α(1-2), α(1-3), and α(1-4) linkages. Recently Weissella sp. has drawn attention for its high dextran production capacity and linearity in its dextran. In our earlier report Weissella confusa Cab3, isolated from fermented cabbage, was explored for its dextransucrase and dextran production capacity. Sequential optimization strategy based on statistical experimental designs was employed to enhance dextran production by Weissella confusa Cab3. A two-level Plackett–Burman design was employed, where six variables were studied for their influence on dextran production. Sucrose, K2HPO4 and Tween 80 were significant variables for dextran production. The combined effect of these nutrients on dextran production were studied using a 23 full-factorial central composite design. A second- order polynomial was established to identify the relationship between the dextran production and the three medium components. The optimal concentrations of variables for maximum dextran production were 6.06% (w/v) sucrose and 1.63% (w/v) K2HPO4 and 0.34% (v/v) Tween 80. The maximum concentration of dextran obtained by predicted model was 29.7 mg/mL. The dextran production medium was validated at shake flask level which was in good agreement with the experimental determined value (28.0 mg/mL). This value of dextran concentration was 3.3 fold higher as compared to unoptimized medium that gave 9.0 mg/mL of dextran. The dextran production from Weissella confusa was scaled up in a 3L bioreactor. At bioreactor level, Weissella confusa efficiently utilized the medium sucrose and produced 29.0 mg/mL of dextran. Keywords: Bioreactor, CCD, contour plot, dextransucrase, dextran, fermentation, lactic acid bacteria, medium optimization, plackett-burman design, scale up, response surface method, statistical method, sucrose, tween 80, Weissella confusa