Catalog
Livestock farming has been a crucial source of high-quality protein and other animal by-products for humans since ancient times. Antibiotics are widely used in livestock to promote growth, treat and prevent diseases, ensuring stable production. However, antibiotic misuse leads to residues in the environment, contributing to the emergence of antibiotic-resistant superbugs, posing a major threat to human health. Globally, at least 700,000 people die annually from drug-resistant diseases, with China notably affected by antibiotic overuse. Urgent measures to reduce antibiotic misuse are imperative, and β-glucan may offer a potential solution.
β-glucans are a group of β-D-glucose polysaccharides naturally found in the cell walls of grains, bacteria, and fungi. Yeast β-glucans, characterized by β-(1,3)-glucosidic linkages forming the main chain and β-(1,6)-glucosidic linkages as branches, can enter the lymph through the intestines, interact with immune cells as immunomodulators, and enhance immune cell activity. They also possess anti-inflammatory and anti-tumor properties, making them promising alternatives to antibiotics. However, current extraction and production methods for β-glucans, including enzymatic, alkaline, acid, and chemical synthesis methods, suffer from complexity, low efficiency, impurities, and high costs.
Our laboratory has identified a marine yeast-like fungus isolated from mangroves, Aureobasidium melanogenum BZ-11, which secretes extracellular polysaccharides including β-glucans efficiently and is suitable for fermentation. This means that extracellular β-glucans can be obtained simply through centrifugation. However, its polysaccharides also contain significant impurities such as melanin and pullulan, and it has limited oxygen uptake capacity, restricting yield and purity. Therefore, we employed synthetic biology techniques, utilizing Cre-loxP technology to block melanin and pullulan secretion, enhancing product purity, and introducing an oxygen uptake system to boost yield. We have continually optimized the nitrogen and carbon sources in the culture medium to facilitate fermentation for β-glucan production.
The β-glucan obtained through centrifugation and freeze-drying can be widely applied in livestock as a feed additive. We believe this can serve as an antibiotic alternative to reduce antibiotic use in feed, addressing the issue of antibiotic misuse effectively.
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