The role of glucose-mediated carbon catabolite repression in flavor formation during fermentation of surimi gel by Actinomucor elegans

Fermented surimi gel quality is governed by microbial metabolism. Adding glucose as a substrate significantly influence fermentation performance, presumably by triggering carbon catabolite repression (CCR). However, the systematic metabolic regulatory mechanisms underlying this effect remain poorly elucidated. This study investigated how varying glucose concentrations (0%, 5%, 10%, 15%, 20%) modulate the solid-state fermentation of surimi gel by Actinomucor elegans using integrated multi-omics analysis. Results showed that moderate glucose supplementation (5-10%) enhanced gel aroma and mycelial thickness, whereas higher levels (>10%) markedly inhibited fungal growth. Biochemical analysis revealed a glucose dose-dependent increase in gel pH and a decrease in protease and aminopeptidase activities with rising glucose, indicating suppressed proteolysis. Transcriptomics demonstrated high reproducibility and a clear dose-dependent transcriptional response. Functional enrichment analysis revealed distinct metabolic reprogramming: low-glucose groups (G5, G10) were uniquely enriched in pathways like sulfur metabolism and fatty acid degradation, while high-glucose groups (G15, G20) converged on amino/nucleotide sugar metabolism. Integrated multi-omics analysis of the key group (G10) versus the glucose-free control (G0) delineated a CCR response, characterized by significant upregulation of key glycolytic enzymes (e.g., hexokinase, pyruvate kinase), driving enhanced production of volatile flavor compounds like ethanol (403.09 μg/kg) and 2-phenylethanol (284.84 μg/kg). Concurrently, the non-volatile metabolome was reshaped, with significant alterations in organic acids (citric, malic, acetic), polyunsaturated fatty acids, and bioactive peptides. Collectively, this study elucidates the glucose-responsive CCR in Actinomucor elegans , providing insights into carbon metabolism redirection and its deterministic role in shaping flavor profiles of fermented surimi.