Production of dextran and fructose from carob pod extract and cheese whey by Leuconostoc mesenteroides NRRL B512(f)

Mariana Santosa, Alírio Rodriguesb and José A. Teixeiraa, ,
aCentro de Engenharia Biológica, Campus de Gualtar, 4710-057 Braga, Portugal
bLaboratory of Separation and Reaction Engineering, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
Received 8 July 2003; revised 11 January 2005; accepted 12 January 2005. Available online 27 April 2005.

Abstract

The production of dextran and fructose from carob pod extract (CPE) and cheese whey (CW) as carbon source by the bacterium Leuconostoc mesenteroides was investigated. The influence of secondary carbon sources (maltose, lactose and galactose) on dextran molecular weight and fermented broth viscosity were also studied.
Significant changes were not observed in broth viscosity during dextran production at initial sucrose concentration of 20 and 120 g/l. Complementary sugars maltose, lactose and galactose together with sucrose promote production of dextran with fewer glucose units. Dextran molecular weight decreases from the range 1,890,000–10,000,000 to 240,000–400,000 Da when complementary sugars are present. Polydispersity was improved when complementary sugars were used.
Fermentation using mixtures of carob pod extract and cheese whey confirm these results obtained for production of dextran. Final concentrations of dextran and fructose indicate that reaction yields were not affected. Carob pod and cheese whey can be successfully used as raw material in the fermentation system described.
The maximum concentrations of dextran and fructose obtained using carob pod extract resulted in 8.56 and 7.78 g/l, respectively. Combined carob pod extract and cheese whey resulted in dextran and fructose concentrations of 7.23 and 6.98 g/l, respectively. The corresponding dextran mean molecular weight was 1,653,723 and 325,829.

Keywords: Dextran; Fructose; Leuconostoc mesenteroides; Viscosity; Molecular weight; Carob pod; Cheese whey
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Biochemical Engineering Journal
Volume 25, Issue 1, August 2005, Pages 1-6