To move towards a circular bioeconomy, sustainable strategies for the utilization of renewable, non-food biomass wastes such as lignocellulose, are needed. To this end, an efficient bioconversion of d-xylose – after d-glucose the most abundant sugar in lignocellulose – is highly desirable. Most standard organisms used in biotechnology are limited in metabolising d-xylose, and also in vitro enzymatic strategies for its conversion have not been very successful. We herein discuss that bioconversion of d-xylose is mostly hampered by missing knowledge on the kinetic properties of the enzymes involved in its metabolism. We propose a combination of classical enzyme characterizations and mathematical modelling approaches as a workflow for rational, model-based design to optimize enzyme cascades and/or whole cell biocatalysts for efficient d-xylose metabolism.