Utilization of Protein-Rich Agricultural Residues in the Biotechnological Production of L-Lactic Acid and 1,3-Propanediol for Added Value

Due to limited fossil resources and climate change, biotechnological processes converting renewable resources into industrial raw materials are increasingly important. Many of these processes require yeast extract for microorganism growth, a high-cost factor. Therefore, the use of inexpensive, protein-rich agricultural raw materials as a source of nutrients is desirable. However, their usage usually results in lower product concentrations and productivity in the fermentation process. This work investigates the nutritional requirements for the production of L-lactic acid using Lactobacillus casei ATCC 393 and 1,3-propanediol using Clostridium butyricum DSM 25047, aiming to replace complex nutrient sources with hydrolyzed protein-rich agricultural raw materials. In the production of 1,3-propanediol, yeast extract was largely (80%) replaced by rapeseed meal hydrolyzate, achieving the same final product concentration and maximum productivity. In the production of L-lactic acid, rapeseed meal hydrolyzate supplemented with B vitamins, mineral salts, cysteine, and tryptophan replaced yeast and meat extracts, achieving the same final product concentration with comparable maximum productivity.