Development of cabbage fermented powder with enhanced enzyme activity using microorganisms isolated from nuruk

This study aimed to produce fermented cabbage powder with enhanced enzyme activity and functionality. Twenty-four strains of Bacillus spp. were isolated from two types of traditional nuruk. Four strains exhibiting superior amylase and protease activities were selected through qualitative and quantitative analyses and identified as two B. subtilis and two B. amyloliquefaciens strains using 16S rRNA sequencing. Among them, B. amyloliquefaciens S2 was ultimately selected as the most suitable strain for cabbage fermentation. A solution containing 10% cabbage powder was fermented with this strain for 24 h, followed by the addition of 5% excipient and freeze-drying; among the excipients tested, mannitol provided the highest enzyme retention. Regardless of excipient addition, the lyophilized cabbage powder maintained nearly 100% enzyme stability after heat treatment at 60°C for 12 h, but its activity decreased by approximately 50% after heat treatment at 90°C for 4 h. Furthermore, sulforaphane content exceeded 100 μg/g (based on original powder) after fermentation, representing an increase of over 100-fold compared to the unfermented sample. These results demonstrate that combining strain screening with cabbage fermentation successfully produces a fermented cabbage powder with significantly enhanced amylase and protease activities, as well as increased sulforaphane content compared to the pre-fermentation state.