Bacterial Diversity and Metabolomic Profile of Castor Oil Bean Seed (Ricinus communis L.) Condiment

Abstract

This study provides a comprehensive characterization of spontaneously fermented castor oil bean condiment (COBC) by integrating metagenomic and metabolomic analyses. High-throughput 16S rRNA sequencing revealed a highly diverse bacterial community (Shannon index = 3.8), with rarefaction analysis confirming adequate sequencing depth. The microbiota was predominantly bacterial (99.0%), largely composed of Bacilliota (83.4%) and Bacilliota A (16.5%), with minor contributions from Actinomycetota (0.3%). At finer taxonomic resolution, Lactobacillales dominated, particularly Atopostipes (51.2%) and Vagococcus A (28.5%), while genera such as Peptostreptococcus and Bacillus A occurred at moderate abundance. This provides a detailed account of bacterial taxa present and their relative proportions, including previously underreported groups. Metabolites were analyzed using gas chromatography–mass spectrometry, revealing 18 volatile organic compounds across nine chemical classes, with esters (28.0%) and amines (22.0%) predominating. The most abundant compound was 9,12-octadecadienoic acid methyl ester (18.86%). Non-volatile compounds were primarily fatty acids, with monounsaturated fatty acids (50%) being most abundant, followed by saturated (37.5%) and polyunsaturated (12.5%) forms. Amino acid analysis identified 17 compounds, with non-essential amino acids predominating; glutamic acid (12.52 mg/100 g) and aspartic acid (7.60 mg/100 g) were highest, while leucine (5.60 mg/100 g) and phenylalanine (4.21 mg/100 g) were the leading essential amino acids. COBC exhibits a distinct microbial and biochemical profile, highlighting its potential nutritional and functional relevance, while providing a high-resolution account of the bacterial community structure, offering a more complete understanding than previously reported using culture-dependent techniques.