In this study, we describe enhanced in vitro probiotic activities of preformed biofilms versus planktonic cultures of Lactobacillus fermentum LfQi6 (LfQi6), a lactic acid bacterium (LAB) isolated from the human microbiome. These evaluations are used to help predict host in vivo probiotic benefits and therefore indicate that LfQi6 may provide significant probiotic benefits in the human host when administered as preformed biofilms rather than as planktonic cultures. Specifically, LfQi6 biofilms demonstrated improved in vitro performance versus LfQi6 planktonic cultures for host gastrointestinal survival and engraftment, strain-specific antimicrobial and anti-biofilm activity against clinically significant pathogens, concurrent promotion of beneficial gastrointestinal commensal biofilms, beneficial commensal enzyme activities, and host cellular-protective glutathione antioxidant activity. Evaluation of LfQi6 according to the European Food Safety Authority (EFSA 2007, 2012, 2015) Guidelines and Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Evaluation of Probiotics in Food (FAO/WHO, 2002) demonstrates strain safety. In summary, in vitro evaluation of Lact. fermentum LfQi6 demonstrates significant evidence for strain-specific probiotic characteristics and safety. Moreover, strain-specific as well as biofilm-phenotype-specific benefits demonstrated in vitro furthermore suggest that in vivo use of LfQi6 biofilm biomass may be of greater benefit to the human host than the use of standard planktonic cultures. This concept - potentiating probiotic benefits through the use of preformed commensal biofilms - is novel and may serve to further broaden the application of microbial biofilms to human health.