New direct production of gluconic acid from polysaccharides using a bifunctional catalyst in hot water

► Pt/AC-SO3H was prepared by the sulfonation of the prepared Pt/AC. ► The bifunctional catalyst had strong acidic sulfo groups and platinum fine particles. ► Gluconic acid was produced from polysaccharides, such as starch and cellobiose. The reaction was done by a one-pot process using the Pt/AC-SO3H catalyst. ► The Pt/AC-SO3H was highly water-tolerant under hot acidic aqueous solutions.