Growth and metabolic behavior of probiotic Bifidobacterium longum subsp. longum in minimally supplemented soy (tofu) whey

Abstract

Soy (tofu) whey is a liquid side-stream from tofu production. It is a nutrient-rich substrate that can be converted into beverages by fermentation. In this study, soy whey media supplemented with various nutrients (control, glucose, glucose + cysteine-HCl (GC), glucose + cysteine-HCl + yeast extract (GCY)) were evaluated as fermentation substrates for probiotic Bifidobacterium longum subsp. longum BB536. GC and GCY facilitated strain BB536 growth leading to the production of acetic and lactic acid. However, there was no significant decrease in sugar content after fermentation, while succinic acid and selected amino acids such as cysteine showed significant decreases after fermentation. Vitamin B12 (2.12 µg/L) was found only in fermented GCY samples. Endogenous volatile compounds such as heptanal and hexenal in tofu whey were reduced to low or trace levels while short-chain fatty acids, 2,3-butanedione and volatile sulfur compounds such as hydrogen sulfide and 3-methylthiophene were produced. Iron and potassium contents in the fermented soy whey increased after fermentation. This research provides further insights into the possibility of utilizing B. longum BB536 to ferment soy whey into a novel functional beverage or ingredient.