Fermented foods such as yoghurt, kimchi and kombucha are often celebrated for their digestive and health benefits. But what is it about fermentation that gives these foods their supposedly healthy edge? How do their nutrients differ before and after?
In a recent study, a team of researchers from the A*STAR Institute of Molecular and Cell Biology (A*STAR IMCB) and A*STAR Institute of Food and Biotechnology Innovation (A*STAR SIFBI) took a dive into tempeh fermentation to examine its molecular-level effects on the humble soybean.
“Tempeh is more than just soybeans inoculated with Rhizopus fungi. Its microbial complexity, culinary potential and nutritional depth are more sophisticated than people realise,” said Jayantha Gunaratne, a Senior Principal Scientist and Head of the Translational Biomedical Proteomics lab at A*STAR IMCB. “The right fermentation and preparation techniques can not only improve tempeh’s flavour and texture, but also enhance its protein profile in ways we’re only starting to understand.”
Gunaratne and colleagues—including Jia Yee Wu, formerly of A*STAR SIFBI and now a Scientist at A*STAR IMCB, and A*STAR Senior Adviser Christiani Jeyakumar Henry—used advanced proteomics and peptidomics tools to study how soybean proteins are broken down by Rhizopus and other microbes during tempeh production. They analysed the mix of peptides—chains of amino acids—released as such proteins are digested by microbial enzymes. The peptides were then compared to those in commercial soybeans.
A major hurdle for the team was the absence of a complete protease database for Rhizopus with which to identify enzymes responsible for protein degradation. Instead, they used a nonspecific enzyme search strategy to infer the types of proteases involved, applying advanced spectral processing and peptide analysis to analyse protein cleavage sites and detect patterns in protein breakdown.
“This approach revealed peptides typically overlooked by conventional analysis, shedding light on the diverse proteolytic activities of the microbes involved,” said Gunaratne.
The team identified over 48,000 peptides derived from soybean proteins after microbial digestion. They also mapped the combined roles of several fungal and bacterial enzymes in enriching tempeh’s nutritional and functional profiles.
Gunaratne highlighted the role of mass spectrometry-based proteomics in their study’s novel findings. These included the reduction of allergenic proteins in tempeh compared to soy, which highlights its potential as a hypoallergenic plant-based protein; as well as the release of insulin-like peptides during microbial digestion that may enhance insulin sensitivity and support metabolic health.
“Proteomics allows us to pick up subtle changes in food composition that conventional methods often miss, making it a powerful tool not just for nutrition research, but also for improving food safety and quality control,” said Gunaratne.
Next, the team aims to investigate the fate of microbially-digested tempeh peptides in the human gut, particularly their interactions with gut cells and microbiota, as well as their potential influence on immunity or gut health.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Molecular and Cell Biology (A*STAR IMCB) and A*STAR Institute of Food and Biotechnology Innovation (A*STAR SIFBI).
