Impact of nutrient from aqueous extract of burdock roots and ultrasonic stress on the growth and β-glucosidase activity of Lactiplantibacillus plantarum FEL112

Abstract

The impact of nutrient and ultrasonic stresses on the growth and β-glucosidase activity (β-GA) of Lactiplantibacillus plantarum FEL112 (Lp-FEL112) was investigated using burdock (Arctium lappa L.) roots as the nutrient source. Three extraction modes, ultrasound at 40 kHz/300 W (U40), 120 kHz/300 W (U120), and shaking at 120 rpm, were compared to get the aqueous-extract of burdock-root containing monosaccharides and polyphenols. Using U40, 50 °C, and 1:30 (g/mL) of solid-to-liquid ratio for 10-min of extraction, the obtained dried aqueous-extract of burdock-root (BWE) was used to evaluate the nutrient stress on the survival of Lp-FEL112. Among various amounts of BWE added in de Man, Rogosa, & Sharpe (MRS) medium (w/v), 1%-BWE induced the highest β-GA (24.31 U/mL) of Lp-FEL112 with the highest antioxidant activity of the fermented product. For 1%-BWE added in black soymilk as the medium (w/v), the β-GA of Lp-FEL112 stimulated using U120 for 20-min was higher than that using U40 for 10-min and 20-min. The nutrient and ultrasonic stresses significantly affected morphological structures of Lp-FEL112. The empirical model using Churchill equation was proposed to appropriately describe the survival of Lp-FEL112. The bacteria acclimated under nutrient and ultrasonic stresses could be applied in the fermentation of burdock-root related foods.