Abstract:

The goal of this work was to explore the mechanism of sedimentation separation of starch by acidic steeping liquor method so as to provide experimental guidance for the development of highly efficient bioflocculant. The Lactobacillus paracasei-fermented sweet potato slurry and its centrifugation supernatant and resuspended precipitate were separately added with sweet potato starch, and the flocculation of sweet potato starch in the three liquors was studied by the determination of Zeta potential, granular size and ionic bond. The flocculation of sweet potato starch was based on the bridging mechanism, and starch granules were conjugated with bacterial cells through ionic bond, and after flocculation, mean starch granular size decreased and granular density increased, resulting in the aggregation and sedimentation of starch granules. Moreover, from the results of experiments on the thermal and enzymatic stability of substances with flocculating activity, proteins were the active components in Lactobacillus paracasei responsible for flocculation.

Key words: Lactobacillus paracasei, sweet potato starch, bridging mechanism