In vitro bioactivities of coffee brews fermented with the probiotics Lacticaseibacillus rhamnosus GG and Saccharomyces boulardii CNCM-I745

Previously, we demonstrated the production of bioactive metabolites (e.g., indole-3-lactate, 4-hydroxyphenyllactate, 3-phenyllactate, 2-isopropylmalate) by the probiotics Lacticaseibacillus rhamnosus GG and Saccharomyces boulardii CNCM-I745 during coffee brew fermentation. However, it remains unclear if in situ production of bioactive metabolites confers additional health benefits to coffee brews. Here, we aimed to investigate the in vitro bioactivities of freeze-dried cell-free coffee supernatants fermented with L. rhamnosus GG and/or S. boulardii CNCM-I745, compared to non-fermented coffee supernatants. In vitro bioactivity assays pertained to α-amylase and α-glucosidase inhibition, antiglycative activities, anti-proliferation against human cancer cell lines (MCF-7, HCT116, and HepG2), cellular antioxidant activities, and anti-inflammatory activities. We demonstrated that non-fermented coffee supernatants displayed weak starch hydrolase inhibition (IC₅₀ > 36.00 mg/mL), but otherwise displayed strong anti-glycative (IC₅₀ 0.71-0.74 mg/mL), anti-proliferative (IC₅₀ 0.45, 0.36, and < 0.5 mg/mL for MCF-7, HCT116, and HepG2 respectively), cellular antioxidant (85,844.22 µmol quercetin equivalents/100 g coffee supernatant), and anti-inflammatory activities (35.7% reduction in nitrite production at 0.13 mg/mL). In all the assays tested, probiotic fermented coffee supernatants exhibited very similar bioactivities compared to non-fermented coffee supernatants, and improvements were not observed. Overall, in vitro bioactivities of coffee brews were not improved via in situ metabolite production by L. rhamnosus GG and/or S. boulardii CNCM-I745. Therefore, bioactive metabolites produced during probiotic-induced food fermentations may not necessarily confer additional health benefits compared to non-fermented counterparts.