Brewer's Spent Grain Enhanced the Recovery of Potential Probiotic Strains in Fermented Milk After Exposure to In Vitro-Simulated Gastrointestinal Conditions

Brewer's spent grain (BSG) is a beer industry by-product with interesting functional properties by its high fiber content and bioactive compounds, which may be possibly employed as a prebiotic ingredient. The fermentability of BSG by ten probiotics and two starter cultures was evaluated, and the co-culture of Lacticaseibacillus paracasei subsp. paracasei F-19 (R) (probiotic) and Streptococcus thermophilus TH-4 (R) (starter) was selected to produce a potentially probiotic fermented milk (FM). Four formulations of FM were studied: FM1 (control), FM2 (probiotic - /BSG +), FM3 (probiotic + /BSG -), and FM4 (probiotic + /BSG +). The viability of the microorganisms in the FM was monitored throughout 28 days of storage. The resistance of the microorganisms in the FM to in vitro-simulated gastrointestinal tract (GIT) conditions was also evaluated. Even though the BSG did not influence the fermentation kinetics or increase the populations of both microorganisms in the FM, a significant improvement on the survival of TH-4 (R) against in vitro-simulated GIT stress was observed in the formulations containing BSG alone or in combination with F-19 (R). All formulations showed potential as probiotic FM, since total probiotic populations were kept above 10(10) CFU in a daily portion of 200 mL, and a minimum of 10(10) and 10(8) CFU equivalent of, respectively, TH-4 (R) and F-19 (R) was recovered after the GIT stress. Therefore, TH-4 (R) has potential as a probiotic strain in addition to its starter feature, while BSG may be employed as a possible prebiotic ingredient in a synbiotic approach. Nonetheless, further studies to evaluate possible health benefits are needed.