Highly branched oligodextran production by acceptor reaction using sucrose and maltose using Leuconostoc mesenteroides

Recently, oligodextrans have received a great attention as potential prebiotic ingredients in food products and animal feeds as alternative antibiotics. Dextransucrase produced by L. mesenteroides polymerizes glucose residue of sucrose by using an insertion mechanism at the reducing end of the growing chain and can produce oligodextran in presence of acceptor sugar. The aim of this research was to investigate the optimization of fermentation processes to produce oligodextran series via acceptor reaction. The strain maintained on medium, the composition of which was yeast extract (0.5 g/L), agar (15 g/l), and sucrose (30 g/l) in mineral medium. The mineral medium (pH 7.0) consisted of K₂H₂PO₄ (3.0g/l), FeSO₄.H₂O (0.01 g/l), MnSO₄.7H₂O (0.01 g), NaCl (0.01 g/l), CaCl₂ (0.05g/l). The effect of sucrose to maltose ratio, culture temperature, culture pH, and co-substrate concentration (sucrose + maltose) on oligodextran yield and productivity, and the size distribution in product was optimized. Oligodextranswere identified and quantified with thin layer chromatography on E. Merck plates 0.25 mm of 1:1 silica gel 60-Kieselguhr. The solvents were methylacetate, ethylacetate, propanol, and water in volume (mL) proportions of 85: 20: 50: 85. At optimum conditions, the yield and productivity were 75.4 % and 2.25 g/l-h and the distribution of oligodextran series was DP 3 (41.4%), DP 4 (13.6%), and bigger than DP 5 (45%).