Development of a synbiotic beverage using Eucheuma cottonii hydrolysate: Fermentation characteristics and enhancement of α-Glucosidase inhibitory activity

Abstract

The development of functional beverages containing probiotics and natural prebiotics has attracted increasing attention due to their potential role in preventing metabolic disorders. This study aimed to develop a synbiotic beverage using Eucheuma cottonii (EC) hydrolysate as a prebiotic source and to evaluate the effects of hydrolysate concentration and fermentation time on microbial growth, physicochemical properties, and α-glucosidase inhibitory activity. The hydrolysate was produced through thermal hydrolysis (100 °C, 3 h), and fermentation was carried out using Lactobacillus plantarum RJ83 with varying hydrolysate concentrations (0, 0.2, 0.4, and 0.6%) and fermentation times (0, 24, and 48 h). Fermentation enhanced lactic acid bacteria (LAB) growth, increased total titratable acidity, reduced pH, and decreased reducing sugar levels, indicating active microbial metabolism. The most intensive fermentation profile was observed in beverages supplemented with 0.6% hydrolysate, whereas the formulation containing 0.4% hydrolysate fermented for 24 h provided the most favorable balance between microbial viability, physicochemical characteristics, and functional properties. This treatment significantly improved α-glucosidase inhibitory activity compared with the control, increasing inhibition from 22.22 ± 0.76% to 92.17 ± 0.28% (p < 0.001). Dose–response analysis using a four-parameter logistic (4PL) model revealed a sigmoidal relationship, with an IC₅₀ value of 1061 ppm, indicating moderate inhibitory activity. These findings suggest that EC hydrolysate contributed substantially to the observed α-glucosidase inhibitory activity and demonstrates strong potential as a functional ingredient for the development of synbiotic beverages with antidiabetic properties.