Abstract: The present disclosure relates to the production of highly efficient heterologous pathways in host cells by identifying favorable enzyme and/or promoter combinations. In particular the present disclosure provides methods for assembly and selection of multi-step xylose and arabinose/xylose utilization pathways from a library of fungal enzymes. The present disclosure further provides compositions containing favorable enzyme combinations, as well as recombinant yeast expressing such combinations, and methods of use for bioconversion of pentose sugars. Also provided are compositions and methods involving favorable expression patterns identified by utilization of combinations of promoters of varying strengths. Provided herein are methods for assembly and selection of multi-step xylose, arabinose/xylose, and cellobiose utilization pathways from a library of promoters of varying strengths.