sentences:  It may also be used in the augmented production of secondary metabolites such as the vinca alkaloids Vincristine and Vinblastine in the rosy periwinkle ("Catharanthus roseus"), whereby space grown specimens often have higher concentrations of these constituents that on earth are present in only trace amounts.From an engineering perspective, facilitating the delivery and exchange of air, food, and water, and the processing of waste products is also challenging.The transition from expendable physicochemical methods to sustainable bioregenerative systems that function as a robust miniature ecosystem is another goal of bioastronautics in facilitating long duration space travel.