Magnetically immobilized edible Bacillus natto for the biotransformation of polydatin to resveratrol and its bioactivity assessment

•Magnetically immobilized Bacillus natto was applied on biotransformation of polydatin to resveratrol firstly.•The novel biotransformation was high-efficiency and eco-friendly.•The immobilized Bacillus natto could be reused at least 3 runs.•The content of resveratrol after biotransformation was 18.18-fold to untreated matrix.•The extracts possessed superior antioxidant and antitumor activities after biotransformation.