A gastrointestinal device and methods of manufacturing said gastrointestinal device are described and include a flexible tubular structure including a layered wall, the flexible tubular structure including at least one microbe-promoting agent encased in the layered wall, the microbe-promoting agent configured to promote at least one of attraction, colonization, and growth of at least one type of commensal microbe, and a proximal end and a distal end, the proximal end and the distal end forming a flow conduit through the flexible tubular structure; and at least one anchor structure including one or more gastric wall-engaging components configured to engage a wall of the gastrointestinal tract of the subject.