The inconsistent microbiota of , the Malaysian fermented anchovy sauce, revealed through 16S amplicon sequencing.

is a Malaysian fermented anchovy sauce produced by immersing small fishes into a brine solution for 6 to 18 months. Microbial enzymes are known to contribute to fermentation; however, not much is known about the microbial community in . Therefore, a better understanding of the microbiome is necessary to improve the quality, consistency, and safety of the products. In this study, we collected 60 samples from 20 bottles of produced by seven manufacturers. We analyzed their microbiota using V3-V4 16S rRNA amplicon sequencing when we first opened the bottle (month 0), as well as 3 and 7 months post-opening (months 3 and 7). was the dominant genus in many samples, reaching a maximum proportion of 98.62%, but was found in low abundance, or absent, in other samples. When samples were not dominated by a dominant taxa, we observed a wider genera diversity such as , , and . While the taxonomic composition was relatively stable across sampling periods, samples from two brands showed a sudden increase in relative abundance of the genus at month 7. Based on prediction of metagenome functions, non--dominated samples were predicted to have enriched functional pathways related to amino acid metabolism and purine metabolism compared to -dominated samples; these two pathways are fundamental to fermentation quality and health attributes of fish sauce. Among the non--dominated samples, contributions towards amino acid metabolism and purine metabolism were biased towards the dominant taxa when species evenness is low, while in samples with higher species evenness, the contributions towards the two pathways were predicted to be evenly distributed between taxa. Our results demonstrated that the utility of 16S sequencing to assess batch variation in fermented food production. The distinct microbiota was shown to correlate with characteristic metagenome function including functions potentially related to fermented food nutrition and quality.