LEMON - Integrated two-stage fermentation process for the development of biorefineries using the example of lemon acid production

Despite significant progress in the development of microbial production strains and fermentation processes, commercial biorefineries using second-generation (2G) feedstocks are still difficult to find. When analyzing the ongoing difficulties in the development of 2G biorefineries, two main obstacles can be identified: First, organic residue or waste streams often contain inhibitors and therefore require extensive detoxification or dilution to serve as substrates for microbial growth. As a result, the end product concentrations of such fermentations are often low, which makes downstream product purification expensive. Secondly, waste streams often contain a complex matrix of mineral salts and organic substances. These compounds are often impossible or very difficult to separate from the final product. The consequences of these impurities range from deviations from the desired color of the product to its complete unusability in subsequent processing stages. From an economic point of view, this means disproportionately high costs for product purification or even a complete failure of the technology.

In this project, these problems are to be solved by developing a novel production process in which three different residual material streams (whey molasses from Sachsenmilch Leppersdorf GmbH, fruit juice sludge from Natursaft-Sachsen GmbH & Co. KG and lignocellulose hydrolysate from UPM Biochemicals GmbH) are to be used as a raw material source for the production of citric acid. This additive is used directly by food companies in their products and therefore does not require separate marketing.