Ludovica Varriale

• The economic and environmental challenges are driving the search for alternative and sustainable energy resources. In this scenario, lignocellulosic biomasses are gaining more attraction due to their high abundance, renewability, and low cost, and can therefore contribute to the development of a bio-based economy. Grass materials from dedicated crops or crop residues can be utilized as feedstock in green biorefinery platforms. In these platforms, the biomass is firstly fractionated into a press-cake and a press-juice. Then, further technologies are applied including the extraction of valuable compounds from the press-juice, and the utilization of the press-cake in feed, material, pulp and paper, and fuel applications. This thesis outlines the development of an innovative green biorefinery platform using the perennial ryegrass Lolium perenne for the production of chemicals. To accomplish this, all the conversion steps— including biomass pretreatment, enzymatic hydrolysis, and fermentation— were carried out to promote the utilization of both the press-cake and the press-juice. Mechanical pretreatment was identified as the most efficient method to get sugars from enzymatic hydrolysis, and to separate the press-cake and the press-juice. Different bioprocesses were investigated to convert the press-cake and the press-juice into the final chemicals. The press-cake was utilized as substrate in a Consolidated Bioprocess where Aspergillus niger was used as a biocatalyst for citric acid production. The nutrient-rich press-juice was exploited in ethanol and lactic acid fermentation. For ethanol production, short-term adaptation was applied to enhance the fermentation capacities of Saccharomyces cerevisiae in pure press-juice. Lactic acid production was ensured by optimizing the press-juice as a fermentation medium at bench- and reactor-scale. Overall, the main findings of this thesis demonstrate that, despite their limitations, lignocellulosic biomasses— including the perennial ryegrass— are valuable feedstocks for the bio-based production of chemicals, fuels, and materials.