High-Yield Vanillin Production Through RSM-Optimized Solid-State Fermentation Process from Brewer’s Spent Grains in a Single-Use Bag Bioreactor

Vanillin is the compound of great interest to the industry. It is used to augment and enhance the aroma and taste of food preparations and also as a fragrance compound in perfumes and detergents. Currently, majority of the world's supply consists of chemically synthesized or lignin-derived vanillin. The application of biocatalysis for sustainable manufacturing of food ingredients, pharmaceutical intermediates, and fine chemicals is the key concept of modern industrial biotechnology. The main goal of this research was to conduct optimization procedures aimed at intensifying the microbial hydrolysis process of the lignin-rich plant raw materials and further bioconversion of the released ferulic acid to vanillin. The tests were performed in the solid-state fermentation system with strains selected during the screening stage on agri-food by-products such as brewer's spent grain. A specially designed single-use bag bioreactor was used to carry out the process on a preparative scale with the most effective strain. The experiment was designed using the RSM, which allowed for an increase in biosynthesis efficiency from 363 mg/kg to 1413 mg/kg (an increase of 389%). The progress of the process was controlled by the use of chromatographic techniques (HPLC) by quantitative determination of vanillin content in the obtained extracts.