Naturally occurring cellulose can be used as a renewable resource for the sustainable production of platform chemicals such as itaconic acid. The biocatalytic conversion of cellulose is a very promising approach due to its high selectivity, mild conditions, and low exergy loss. However, such biocatalytic processes are still seldom applied at the industrial scale since the single conversion steps (pretreatment, hydrolysis, and fermentation) exhibit low efficiencies or high costs. To allow a knowledge-based optimization, each step was analyzed in detail within this thesis. Thereby, new (integrated) approaches and screening technologies were also established. Within this thesis, a detailed understanding of the biocatalytic conversion of cellulose to itaconic acid was generated. Not only all essential conversion steps were investigated in detail, but also novel (integrated) approaches as well as technologies were developed. In the future, the conversion steps need to be further harmonized, and (in-situ) product recovery should be implemented, as well as the recycling of water, cellulases, microorganisms, and unconverted cellulose. Moreover, cellulases and microorganisms need to be improved and adapted to integrated process configuration such as SSF. In conclusion, the results presented within this thesis are the fundamental basis for a further knowledge-based improvement and pave the way for an economically feasible production process converting cellulose to itaconic acid
