Fermentation-driven biotransformation of a carob-based yogurt alternative enhances antioxidant responses in human keratinocytes

Thanks to its ecological and economic advantages, as well as numerous beneficial effects on human health, carob-based fermented products are ideal candidates for the development of functional foods that can also contribute to the Sustainable Development Goals. In this study, a plant-based yogurt alternative was developed using carob and rice flour fermented with selected lactic acid bacteria. All the strains showed good pro-technological performances (fast acidification and growth up to 9 log cfu/g), as well as the ability to increase DPPH radical scavenging activity compared to unfermented control (on average 74 against 61 %), but Lactiplantibacillus plantarum 18S9 was selected as the optimal starter. HPLC-ESI-Q/TOF profiling revealed major fermentation-driven modifications in phenolic composition, including the generation of pyrogallol. Whereas assays on human keratinocytes showed that both unfermented and fermented gurts mitigated H₂O₂-induced oxidative stress, with G-18S9 eliciting stronger regulation of genes encoding for enzymes involved in oxidative stress protection (SOD2 and HMOX-1). These findings provide supporting evidence linking microbial biotransformation of carob phenolics to improved antioxidant defenses in human cells, underscoring the potential of fermentation to enhance the functional value of underutilized plant ingredients and highlighting a promising route for producing high-value, sustainable yogurt alternatives that combine technological stability, consumer acceptability, and health-promoting properties.