Lipase production by solid-state fermentation on distiller's dried grain with solubles in a biorefinery approach: Optimization and techno-economic analysis

This work proposes a biorefinery process from the corn ethanol industry to produce a low-cost dry-fermented solid biocatalyst and enzymatic biodiesel. The fermentation conditions (temperature, moisture, and spore concentration) were optimized through a design experiment. In the best conditions (27 °C, 65 % moisture content, and 1.00 × 10⁷ spores from Rhizopus oryzae/g of solid), it was possible to obtain 80 % conversion of oleic acid and ethanol to ester in 24 h of reaction. A solid pre-inoculum strategy was used to scale up the biocatalyst production by 100 times. The simulation in three different scenarios and its techno-economic analysis – made using the software SuperPro Designer – answered questions related to the feasibility of the biocatalyst production. In the best scenario, the unitary production cost was US$ 3.47/kg. Selling this product for US$ 7.30/kg would represent more than 100 % profit and a payback time of 1.46 years.