This research was carried out in order to discover acid-forming bacteria during fermentation of Makgeolli, as Makgeolli loses its commercial value due to overproduced acidic materials. In Makgeolli kept at 25℃, a sudden increase of acidity as well as the disappearance of yeast cells occurred at day 6, whereas the total cell count and bacterial type remained unchanged; the result implies that a succession of bacterial types, including acid forming bacteria, occurred. Two acidforming bacteria were isolated from acidified Makgeolli and were identified as Acetobacter pasteurianus and Lactobacillus casei. When fresh and heat-treated Makgeolli were inoculated with Acetobacter pasteurianus and/or Lactobacillus casei, the greatest amount of acid was formed in Makgeolli inoculated with Acetobacter pasteurianus and Lactobacillus casei and also in Makgeolli with Acetobacter pasteurianus alone. This result indicates that Acetobacter pasteurianus is the main acidifier; furthermore, it shows the synergy effect in acid formation with Lactobacillus casei.

This research was carried out to find herbal preservatives for Makgeolli, as Makgeolli loses its commercial value due to overproduced acidic materials. When Makgeolli was kept at 25℃ to find the changes in acidity, total microbial cell number, yeast cell number, and bacterial species variety, a sudden increase of acidity as well as the disappearance of yeast cells occurred at day 6, and Makgeolli was changed to complete off-flavor. Acetobacter pasteurianus is the main acidifier in Makgeolli and shows a synergy effect in acid formation when cultured in combination with Lactobacillus casei. Among 12 herbs, the ethanol extract of Sutellaria baicalensis showed antimicrobial activity against A. pasteurianus, whereas the ethanol extract of Coptidis rhizoma showed antimicrobial activity against L. casei. Makgeolli added with Sutellaria baicalensis extracts demonstrated a lower acidity than that with Coptidis rhizoma extracts, which indicates that the inhibition of an acetic acid former is more important than that of a lactic acid former in Makgeolli preservation. Sutellaria baicalensis extracts prolonged the shelf life of Makgeolli by 1～2 weeks at a minimal inhibitory concentration (0.63 ㎎/㎖) during storage at 10℃.