Lactic acid bacteria-driven biotransformation of blue crab (Callinectes sapidus) carapace generates extracts with...

The invasive blue crab Callinectes sapidus generates substantial carapace-rich side streams which disposal represents an environmental and economic burden in Mediterranean coastal areas. This study investigated whether lactic acid bacteria (LAB) fermentation could promote the biotransformation of blue crab carapace and yield bioactive extracts of potential relevance for food preservation and metabolic modulation. Carapace powder was inoculated with six LAB strains, and the resulting hydroethanolic extracts were assessed for antimicrobial activity in vitro against major foodborne pathogens and in a ready-to-eat fish soup challenge test. Metabolic effects were evaluated in zebrafish larvae, while untargeted LC-MS/MS metabolomics and feature-based molecular networking were used to investigate extract composition. Limited bacterial growth was observed although most strains remained viable and produced mild pH changes, indicating persistence and LAB-driven biotransformation rather than intense acidification. All extracts showed antimicrobial activity in vitro against Salmonella enterica. The extracts obtained with Lacticaseibacillus rhamnosus UPCCO 1473 and Lacticaseibacillus casei UPCCO 2240 were tested in situ in a fish soup model, where the inhibition was mainly observed at the highest tested concentration (40 mg/mL), particularly under temperature-abuse conditions. At 25 μg/mL, both fermented and non-fermented extracts reduced lipid accumulation in zebrafish larvae, with strain-dependent differences among fermented samples. Selected extracts also increased glucose uptake, while one reduced appetite. Metabolomic analysis revealed distinct but partially overlapping chemical profiles, including putatively annotated fatty acyls, carboxylic acid derivatives, bile-acid-related compounds, and saponin- or triterpenoid-like compounds. These findings provide proof-of-concept that LAB biotransformation can modulate the functional properties of blue crab carapace in a strain-dependent manner. However, compound identification, dose-response assessment, safety evaluation, and validation under realistic exposure and food-application conditions are required before practical use can be proposed.