Revisiting the Role of Lactic Acid Bacteria in Cacao Fermentation: From Traditional Paradigm to Functional Precision.

The role of lactic acid bacteria (LAB) in cocoa bean fermentation has long been considered central within the traditional yeast-LAB-acetic acid bacteria (AAB) succession model. However, their functional necessity for successful fermentation remains debated. While yeasts and AAB are consistently associated with key transformations such as pulp degradation, ethanol formation, ethanol oxidation, heat generation, and internal bean modification, increasing evidence indicates that cocoa fermentation can proceed effectively under minimal, transient, or reduced LAB activity. This review re-examines the presumed indispensability of LAB using a function-based framework that distinguishes microbial contributions according to their relationship with fermentation completion and process optimization. By integrating evidence from controlled fermentations, microbial suppression studies, starter-culture research, and recent ecological and multi-omics analyses, this review suggests that LAB are better interpreted, under the conditions reported to date, as context-dependent modulators rather than universal core drivers of fermentation completion. LAB contribute to acid balance, citrate metabolism, mannitol production, microbial interactions, ecological stabilization, and quality modulation; however, available evidence indicates that the principal biochemical transformations defining fermentation completion can occur when yeast and AAB activities remain preserved. These conclusions should be interpreted with caution, as direct experimental evidence remains limited and is largely derived from controlled or small-scale fermentation systems. This function-oriented perspective shifts the focus from taxonomic recurrence to biochemical necessity and provides a rational basis for designing starter cultures centered on pathway coverage, metabolic performance, process consistency, and cocoa quality.