Value-Added Utilization of Protein Rich Agricultural Residues—Development and Evaluation of Chemical Hydrolysis

Abstract The chemical industry’s reliance on fossil raw materials has significantly contributed to increased CO 2 levels. To reduce the climate footprint, renewable resources must replace fossil ones. Biotechnical production of industrial chemicals using renewable resources is a promising approach. However, many biotechnical processes require yeast extract, a costly nutrient source. Inexpensive, protein-rich substitutes like agricultural residues can be used instead. To improve fermentation results, a hydrolysis process was developed and tested. This paper describes the optimization of chemical hydrolysis for protein-rich agricultural raw materials like Distillers’ Dried Grains with Solubles (DDGS) and rapeseed meal (RM). The hydrolysates were used as a nitrogen source in bioprocesses to verify their usability. The results show that the amount of free amino nitrogen increases with increasing molarity of the acid. In order to achieve acceptable amino nitrogen concentrations with reduced sulfuric acid molarity, the temperature was raised up to 160 °C. This temperature increase resulted in 81.3% of the amino nitrogen concentration with 1 M sulfuric acid compared to using 3 M sulfuric acid. As a result of this optimization, the costs of the hydrolysated rapeseed meal are reduced to only 8–13% of the original costs of yeast extract with the same nitrogen content. Graphical Abstract