Engineered E. coli turns kimchi radish waste into biodegradable bioplastic

South Korea's kimchi industry processes roughly 132,000 metric tons of radish annually, generating about 17,000 metric tons of inedible by-products that are largely discarded as food waste. Researchers at the World Institute of Kimchi (WiKim) enzymatically hydrolyzed this radish waste into a sugar-rich feedstock and used it as the sole carbon source for engineered Escherichia coli to produce poly(3-hydroxybutyrate), or P(3HB), a bioplastic that microorganisms can naturally degrade.

Instead of relying on trial-and-error strain development, the team led by Dr. Jung Eun Yang performed comparative RNA sequencing on E. coli grown in radish hydrolyzate and integrated the transcriptomic data into a genome-scale metabolic model (iML1515). The model predicted that simultaneous deletion of the gltA and acnA genes would redirect metabolic flux toward P(3HB) biosynthesis.

The engineered strain carrying those deletions accumulated P(3HB) at 71.95% of dry cell weight, a 78% increase over the parental strain when cultured in radish hydrolyzate. In a fed-batch fermentation using the same waste-derived feedstock, the strain reached a final P(3HB) concentration of 5.75 g/L with the polymer constituting 75.60% of dry cell weight.

The study, published in Bioresource Technology, demonstrates that agricultural waste can serve as an efficient feedstock for microbial bioprocessing, outperforming conventional glucose medium in P(3HB) accumulation. The researchers emphasize that the genome-scale model-guided framework is adaptable to other agricultural residues, such as Chinese cabbage by-products, by tailoring strain engineering to the specific metabolic response elicited by each feedstock.

Dr. Yang stated that the strategy enables microbial strains to be engineered according to the metabolic characteristics of individual agricultural waste streams, potentially expanding the utilization of by-products and accelerating sustainable bio-based manufacturing. The work was supported by the National Research Council of Science and Technology.