Diversity and Succession of Microbiota during Fermentation of the Traditional Indian Food Idli

Abstract

Idli, a naturally fermented Indian food, is prepared from a mixture of rice and black gram (lentil). To understand its microbial community during fermentation, detailed analysis of the structural and functional dynamics of the idli microbiome was performed by culture-dependent and -independent approaches. The bacterial diversity and microbial succession were assessed at different times of fermentation by 16S rRNA amplicon sequencing. Results highlighted that most microbiota belonged to phylum Firmicutes (70%) and Proteobacteria (22%). Denaturing gradient gel electrophoresis (DGGE) and quantitative PCR (qPCR) analysis confirmed the diversity and succession involved therein. A culture-dependent approach revealed that the microbially diverse populations were conserved across different geographical locations. The fermentation was primarily driven by lactic acid bacteria as they constitute 86% of the total bacterial population, and genus Weissella emerged as the most important organism in fermentation. The natural microbiota of the grains mainly drives the fermentation, as surface sterilized grains did not show any fermentation. Growth kinetics of idli microbiota and physicochemical parameters corroborated the changes in microbial dynamics, acid production, and leavening occurring during fermentation. Using a metagenomic prediction tool, we found that the major metabolic activities of these microbial fermenters were augmented during the important phase of fermentation. The involvement of the heterofermentative hexose monophosphate (HMP) pathway in batter leavening was substantiated by radiolabeled carbon dioxide generated from D-[1-14 C]-glucose. Hydrolases degrading starch and phytins and the production of B vitamins were reported. Moreover, culturable isolates showing beneficial attributes, such as acid and bile tolerance, hydrophobicity, antibiotic sensitivity, and antimicrobial activity, suggest idli to be a potential dietary supplement. IMPORTANCE This is a comprehensive analysis of idli fermentation employing modern molecular tools which provided valuable information about the bacterial diversity enabling its fermentation. The study has demonstrated the relationship between the bacterial population and its functional role in the process. The nature of idli fermentation was found to be more complex than other food fermentations due to the succession of the bacterial population. Further studies using metatranscriptomics and metabolomics may enhance the understanding of this complex fermentation process. Moreover, the presence of microorganisms with beneficial properties plausibly makes idli a suitable functional food.

Selection of cereal-sourced lactic acid bacteria as candidate starters for the baking industry

“…confusa are concerned, most of them had low (+) or no phytase activity (-). For this species, a very different picture emerged from the study of Mandhania et al [ 53 ], where all the strains assayed produced phytases.…”

“…As far as the isolates ascribed to W. confusa are concerned, most of them had low (+) or no phytase activity (-). For this species, a very different picture emerged from the study of Mandhania et al [53], where all the strains assayed produced phytases. Table 3 reports the results of the LAB screening for EPS production on SSM agar supplemented with 5% sucrose.…”

Fermentative Foods: Microbiology, Biochemistry, Potential Human Health Benefits and Public Health Issues

“…LAB bacteria, which are a complex/compound of Gram-positive bacteria and one of the main microorganisms used in the production of fermented product, can be found within the Firmicutes group (Table 2). It should be emphasized that the Phyla Cyanobacteria are found in fermented butter and a rice cake called Idli, but researches have assumed that the isolated cyanobacterial sequences correspond to cereal chloroplasts [90].…”

Effect of Rice Processing towards Lower Rapidly Available Glucose (RAG) Favors Idli, a South Indian Fermented Food Suitable for Diabetic Patients

“…Foods containing RS cause continuous insulin discharge; this causes the eradication of lipids to be elevated in the liver and is ultimately utilized for energy (Figure 6). Accordingly, RS assumes a critical role in the insulin reaction balance and in managing glucose digestion [32,47]. As an outcome, the use of RS-rich nourishment is imperative in the management of body weight and obesity and in diminishing the danger of developing diabetes and other significant illnesses.…”