Fermentation and microbial characteristics of sorghum-integrated Makgeolli using different saccharification agents Koji and Nuruk

This study evaluated sorghum as a partial substitute for rice in Makgeolli brewing and compared fermentation characteristics between two saccharification agents, koji and nuruk. Makgeolli was prepared with 75% rice and 25% sorghum, and physicochemical properties and microbial communities were analyzed using culture-dependent and culture-independent (16S rRNA and ITS sequencing) methods. During fermentation, pH decreased below 3.5 in all treatments. Lactic acid bacteria exceeded 7 log CFU/mL in nuruk Makgeolli but were not detected in koji Makgeolli by culture-based methods, whereas 16S rRNA sequencing identified Firmicutes and lactic acid bacteria in both fermentations. ITS analysis showed Aspergillus spp. dominance in koji and Saccharomycopsis fibuligera in nuruk. Sorghum substitution did not significantly affect acidification or microbial succession. These results demonstrate that sorghum can be incorporated into Makgeolli without altering fermentation behavior and highlight the value of combining culture-dependent and sequencing approaches to characterize microbial dynamics.