Optimization of process conditions for enzymatic modification of alternan using dextranase from Chaetomium erraticum

Alternan is a unique branched glucan with alternating α-(1 → 6) and α-(1 → 3) backbone linkages. We previously described the modification of alternan to a reduced molecular weight form using dextranase from Penicillium sp. The solution viscosity properties of this modified alternan resemble those of commercial gum arabic. In this study we optimize process conditions for modification of alternan using commercial dextranase from Chaetomium erraticum. This enzyme is considered GRAS (generally regarded as safe) and thus suitable for potential food applications. Optimal conditions were 10% alternan, pH 4.5, 50 °C, and 125 IU dextranase/ml (assayed at 28 °C, pH 5.0). Using these conditions, we scaled up production of modified alternan, permitting for the first time the isolation of separate peaks of modified alternan. Methylation analysis revealed a loss of linear 1,6 linkages during modification. Optimized conditions will be useful to produce modified alternan for applications testing.