Shotgun metagenomics and physicochemical insights into the effects of temperature on bacterial community and related metabolism in fermented skates

Fermented skate, an indigenous fermented fish, is traditionally produced by spontaneous fermentation in Korea, wherein the fermentation temperature plays a vital role. To understand the effect of fermentation temperature on fermented skate, this study investigated the impact of fermentation temperature on the quality characteristics and microbial diversity of skates during fermentation at 25 and 10 & DEG;C. The physicochemical properties of the skate, including the pH, color, textural profiles, trimethylamine nitrogen, total volatile base nitrogen, ammonia nitrogen, and urea contents, were determined during weeks 1 and 2 of fermentation at 10 and 25 & DEG;C, respectively. In addition, the microbial diversity of the fermented skates at 25 and 10 & DEG;C was compared by shotgun metagenomic sequencing. This study also examined the correlation between physicochemical and metagenomics. At the genus level, Paenalcaligenes, Clostridium, and Bacillus were the predominant bacteria in the skate sample fermented at 25 & DEG;C, whereas the dominant genera in the skate fermented at 10 & DEG;C were Psychrobacter and Sporosarcina. At the species level, Psychrobacter sp. DAB_AL43B and Psychrobacter arcticus were predominant species in the skate fermented at 10 & DEG;C, whereas Paenalcaligenes hominis and Erysipelothrix rhusiopathiae were predominant species in skate fermented at 25 & DEG;C. Based on these results, it was observed that the fermentation temperature affected the fermentation period and quality and the bacterial abundance at the endpoint of fermentation in the fermented skate. These results can serve as a valuable resource to produce high-quality fermented skates at appropriate fermentation temperature.