Screening of Starch Flocculation Bacteria in Sweet Potato Sour Pulp, Optimization of Flocculation Conditions and Analysis of Flocculation Components

To enhance the sour pulp processing of sweet potato starch, lactic acid bacteria with starch flocculation ability were isolated from naturally fermented sour pulp. Through single-factor and Box-Behnken response surface experiments, optimal flocculation conditions were determined. Additionally, flocculation-active cellular components were characterized. Results showed that five lactic acid bacteria, including Lactiplantibacillus plantarum HS1, Loigolactobacillus coryniformis HS2, Latilactobacillus sakei HS3, Leuconostoc mesenteroides HS4, and Latilactobacillus curvatus HS5, were isolated from naturally fermented sweet potato sour pulp using MRS medium. Among them, L. plantarum HS1 had the highest starch flocculation ability. Using single-factor experiments combined with a Box-Behnken design, the optimal flocculation conditions for starch by strain HS1 were identified as fermentation temperature 34 ℃, fermentation time 44 h, and fermentation broth addition rate of 10%. Under these conditions, the measured flocculation rate of sweet potato starch was 64.1%±1.87%. Through analysis of flocculating activity distribution and the effects of heating, metal ion addition, and enzyme treatment, it was demonstrated that HS1’s flocculation-active component primarily resided in the fermentation supernatant. Furthermore, this component exhibited sensitivity to temperature, protease, and metal ions, supporting the hypothesis that it is an extracellular protein.