Screening of Aspergillus recifensis EC-1 in Urea-Exposure Fermented Grains: Ethyl Carbamate Metabolic Mechanism, and Application Potential of the Degrading-Microbe and -Enzyme in Baijiu

Ethyl carbamate (EC) poses a potential public health risk; the reduction efficiency is limited by high ethanol and acidic conditions during fermentation. This study identified fungi as key EC-degrading microbes from Baijiu fermented grains. Aspergillus recifensis. EC-1 isolated from Baijiu fermented grains degraded 50.7% EC (5 g·L⁻¹) in 7 days. Transcriptomics and metabolomics revealed EC hydrolysis via amidase into ammonia and ethanol: ammonia entered arginine biosynthesis, while ethanol fueled central carbon metabolism. TR3859 was identified as degrading enzyme. It remained highly active under 20% ethanol and 15% NaCl conditions (9.1 U·mg⁻¹ and 38.8 U·mg⁻¹), and the enzyme's affinity for EC was Km = 6.0 mM. When coculture with strain EC-1 and Daqu, EC degradation reached 81.5% within 3 days, and the relative abundance of the genera Thermoascus and Thermomyces exceeds 65%. The objective of this study was to provide an efficient method for EC elimination in fermented foods by microbes and enzymes.