Gut bacteria turn chicken cartilage waste into joint supplement gold

Every year, the poultry industry generates mountains of cartilage-rich by-products that most processing plants treat as low-value waste. A new study published in the journal 3 Biotech suggests that a common soil bacterium could transform that discarded material into one of the most sought-after ingredients in the joint health and nutraceutical markets. A team of researchers at Henan Agricultural University in Zhengzhou, China, has demonstrated that fermentation with Bacillus velezensis 259 can extract chondroitin sulfate from chicken cartilage with an efficiency that rivals conventional chemical methods, while avoiding some of their most problematic drawbacks.

Chondroitin sulfate is a sulfated glycosaminoglycan, a long-chain sugar molecule decorated with sulfate groups that forms a critical structural component of cartilage. It is widely sold as a dietary supplement for osteoarthritis, often paired with glucosamine, and it also finds uses in pharmaceutical formulations, cosmetics, and tissue engineering scaffolds. Traditionally, manufacturers obtain it by boiling animal cartilage in alkaline solutions or by treating it with commercial enzymes, processes that are energy-intensive, generate chemical effluent, and can degrade the delicate sulfation patterns that give the molecule its biological activity.

The Chinese team took a different route: instead of adding purified enzymes from outside, they let the bacterium produce its own. Bacillus velezensis 259 was first screened for gelatinolytic and proteolytic activity, meaning its ability to break down gelatin and proteins, the very tasks required to loosen the protein-chondroitin sulfate complexes that hold cartilage matrix together. In cartilage, chondroitin sulfate chains are covalently attached to core proteins such as aggrecan, forming giant proteoglycan complexes embedded in a dense collagen network. Freeing the sugar chains requires digesting both the core proteins and enough of the surrounding matrix to let the glycosaminoglycans diffuse into solution.

Before committing to the fermentation strategy, the researchers sequenced the entire genome of B. velezensis 259 to understand its enzymatic toolkit and, crucially, its safety profile. Whole-genome analysis allowed them to examine the organism’s genomic features and to search specifically for potential virulence factors and antimicrobial resistance genes. This step matters because any microorganism used to process food-grade raw material must not carry genes that could pose risks to consumers or facilitate the spread of antibiotic resistance. The genomic interrogation, combined with phenotypic assessment of the strain’s safety-related characteristics, supported the case that the bacterium was a suitable candidate for food bioprocessing applications.

With the strain vetted, the team turned to the engineering problem of maximizing yield. They identified three variables with the strongest expected influence on extraction efficiency: the amount of bacterial inoculum added to the fermentation, the proportion of cartilage in the reaction mixture, and the duration of fermentation. Single-factor experiments first mapped out how each parameter behaved in isolation, revealing the range of conditions under which extraction climbed, plateaued, or declined as cells exhausted nutrients or enzymes degraded the very product they were liberating.

To squeeze out the best possible performance, the researchers then applied a statistical technique called response surface methodology, using a Box-Behnken experimental design to fit a quadratic polynomial model to the data. This approach allows experimenters to explore interactions between variables, for example how inoculum size and fermentation time jointly affect yield, without running every possible combination of conditions. The fitted model predicted a distinct optimum, and the response surfaces confirmed where the sweet spot lay in three-dimensional parameter space.

The optimized protocol called for a 6.2 percent inoculation amount, a 22.5 percent cartilage addition amount, fermentation at 37 degrees Celsius with shaking at 180 revolutions per minute, and a fermentation time of 20.8 hours. Under these conditions, the chondroitin sulfate extraction rate reached 17.9 percent. That figure represents the proportion of the valuable molecule recovered from the starting cartilage material, and it establishes microbial fermentation as a competitive alternative to hot-alkaline extraction and steam explosion methods that other groups have developed for chicken sternal cartilage in recent years.

Yield alone is not enough; the product must also be authentic. The researchers therefore analyzed their crude extract with ultraviolet and Raman spectroscopy, two complementary techniques that probe molecular structure. Ultraviolet spectroscopy captures the absorption signature of the molecule’s sugar backbone and sulfated groups, while Raman spectroscopy detects vibrational modes that are exquisitely sensitive to sulfation position and molecular conformation. The spectral features of the fermented extract closely matched those of chondroitin sulfate type A and type C reference standards, indicating that the microbial process had liberated structurally intact chondroitin sulfate rather than a degraded or contaminated product.

The implications extend beyond a single lab-scale process. Chicken sternal cartilage, the tissue between the breast meat and the bone, is one of the most abundant cartilage streams in poultry processing, and previous work has valued it as a source of both type II collagen and chondroitin sulfate. By using a living bacterium rather than purchased enzyme cocktails, the fermentation approach could cut input costs for manufacturers, since B. velezensis can be grown cheaply and the enzymes are produced in situ. The moderate 37-degree operating temperature and relatively short fermentation time of about 21 hours also suggest modest energy requirements compared with high-temperature or high-pressure methods such as steam explosion and hot-pressure liquefaction.

There remain hurdles between bench and factory. The 17.9 percent extraction rate describes a crude extract whose purity, molecular weight distribution, and sulfation pattern would need further characterization before regulatory and commercial standards for nutraceutical-grade chondroitin sulfate could be met, a challenge the analytical chemistry literature has repeatedly flagged for this notoriously variable material. Scaling a fermentation that mixes dense cartilage solids with living bacteria also poses questions of sterility control, consistency, and downstream purification. Still, by pairing whole-genome safety screening with rigorous statistical process optimization, the Henan Agricultural University team has laid out a complete blueprint for a cleaner, biology-driven way to turn poultry waste into a product that millions of people take to protect their own cartilage.

Subject of Research: Microbial fermentation extraction of chondroitin sulfate from chicken cartilage using Bacillus velezensis 259

Article Title: Extraction of chondroitin sulfate from chicken cartilage by Bacillus velezensis 259 fermentation: whole-genome analysis and process optimization

Article References: Ding, Y., Liu, S., Bai, Y., Ma, Y., Li, M., Liang, D., Ding, Q., Liu, Y., Sun, L., & Liu, Y. (2026). Extraction of chondroitin sulfate from chicken cartilage by Bacillus velezensis 259 fermentation: whole-genome analysis and process optimization. 3 Biotech, 16(11), Article 464. https://doi.org/10.1007/s13205-026-05101-6

Image Credits: AI Generated

DOI: 10.1007/s13205-026-05101-6

Keywords: chondroitin sulfate, Bacillus velezensis 259, chicken cartilage, microbial fermentation, whole-genome analysis, response surface methodology, process optimization, food waste valorization, Raman spectroscopy, bioprocess engineering, gelatinolytic activity, 3 Biotech