Cultivation of heterotrophic algae on paper waste material and digestate

This study investigates the cellulases-catalyzed hydrolysis of newspaper waste and paper slurries as carbon source in combination with digestate from anaerobic digestion as nitrogen source for the heterotrophic cultivation of Chlorella sorokiniana. The enzymatic hydrolysis of paper slurries resulted in a hydrolysate containing 27.2 g l−1 glucose reflecting a 78% cellulose conversion. A maximum Chlorella sorokiniana biomass yield of 3.64 g l−1 was achieved within 91 h of cultivation under consumption of 9.7 g l−1 glucose. The most efficient cultivation converted 1 g l−1 glucose into 0.42 g l−1 biomass. A strong decrease in pH of the batch cultures due to ammonium consumption and CO2 production by algae cells inhibited full glucose consumption for high concentrations of 17 g l−1 glucose. Characterizing the amino acid content and pattern of the biomass revealed an amino acid fraction of 32.9% with Alanine as the most frequent amino acid.