Microalgae like cyanobacteria and cyanidiales can efficiently use nutrients present in wastewater to fix CO₂ into carbohydrates for a subsequent conversion into high-value compounds. However, the composition of their thick wall hinders the degradation of biopolymers and final products as feed stocks in microbial fermentation. In WP6, we aim to investigate the biomass from microalgae and to optimize the enzymes capable of its effective degradation.

First, we will characterize the cell wall composition of cyanobacteria and cyanidiales using different fractionation techniques and subsequent amino acid and lipid identification as well as monosaccharide composition and glycosidic linkage analyses. For cyanidiales, endogenous hydrolases expressed during the life cycle transition between haploid and diploid phases will be selected from genome databases and heterologously expressed in yeast or E. coli. We will also test other enzyme candidates for their ability to degrade microalgal biomass into oligo- and monosaccharides, peptides and amino acids. In addition, the substrate specificities and kinetic parameters of the selected enzymes will be determined and activity and stability will be optimized by rational protein engineering and directed evolution if needed. Efficient degradation of exopolysaccharides and intracellular lipids, proteins and carbohydrates will be achieved by a cocktail of proteases, lipases, cellulases and other enzymes of the glycoside hydrolase family. The degraded monomers will be also used as a feedstock for the cultivation of beneficial microorganisms.