Cost-effective fermentation of fuels and chemicals from second generation sugars has a huge potential for replacing fossil-based feedstocks. Enzymatic saccharification of lignocellulosic biomass streams with (hemi)cellulases is essential to produce monomeric sugars for the production of fuel and chemicals. Yet, saccharification of heterogeneous lignocellulosic streams from circular use of biomass or the biorefinery of crops remains a too high cost factor, and often requires empirical and tedious optimization of enzyme cocktails. I aim to create industrial yeast strains that have the unique capacity to self-adjust their enzymatic arsenal depending on the composition of the available biomass (‘designer cellulosomics’). Designer cellulosomes are engineered multi-enzyme complexes comprising (hemi)cellulases, with an improved degradation efficiency. Specifically, I aim to construct a yeast population with each cell producing a cellulosome with different enzyme composition. By evolutionary experiments, I will create self-enriched yeast subcommunities that are trained for specific lignocellulosic side streams. While I will focus on the non-recyclable fraction of recycled paper pulp and corn bran, the concept can be broadly expanded to any lignocellulose-rich feedstock. By combining bulk production (bioethanol) and high added value fine chemical (flavonoids) production with such strains, I aim to increase the overall profitability and sustainability of biomass processing.