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Metabolic engineering – the improvement of cellular activities by manipulation of enzymatic, transport and regulatory functions of the cell – has enabled the industrial production of a wide variety of biological molecules from renewable resources. Microbial production of fuels and chemicals thereby provides an alternative to oil-based production. To compete with petrochemistry, not only the kinetics of product formation, but also the product yield needs to be optimized. Whereas reduction of byproduct formation, modification of redox-cofactor balances and optimization of the stoichiometry of product formation is studies in many laboratories, the ATP yield of product formation is often overlooked, although it is of paramount importance for the product yield that can be obtained. In this thesis, several opportunities for improvement of free-energy (ATP) conservation in the yeast Saccharomyces cerevisiae, a key industrial microorganism, were investigated. For product pathways with excess ATP and biomass formation, a widely applicable strategy (relocating sucrose hydrolysis) was presented to decrease free-energy (ATP) conservation and thereby increase the product yield. On the other hand, the efficiency of free-energy (ATP) conservation was increased by expression of a maltose phosphorylase, which forms the basis for further development of these strategies towards increasing the ATP yield of many industrial target pathways and specifically to potentially enable efficient anaerobic homolactate production with S. cerevisiae.