Statistical Optimization and Scale-Up of Lipase Production Using Brassica Seed Cake in a Stirred Bioreactor

Abstract

Fungal lipases, particularly from Aspergillus species, are valued for their stability and high yield under optimized fermentation conditions. Agro-industrial residues such as Brassica seed cake provide a cost-effective and sustainable substrate for large-scale enzyme production. This study aimed to optimize and scale up lipase production from Aspergillus sojae using statistical approaches in a stirred bioreactor with emphasis on agro-waste utilization for potential industrial applications. A potent lipase-producing fungal isolate (Aspergillus sojae TB-MS) was cultivated. Preliminary trials were conducted in 250 mL Erlenmeyer flasks, followed by scale-up in a 5-liter stirred fermenter. Key substrates, including Brassica seed cake (complex carbon and nitrogen source), molasses (sucrose as a carbon source), sunflower oil (inducer and lipid substrate), sucrose (readily metabolizable carbon source), yeast extract (organic nitrogen source), and Tween 80 (emulsifier and lipase activity enhancer), were screened using a one-factor-at-a-time (OFAT) approach. Response Surface Methodology (RSM) was applied to evaluate the interactive effects of the components. Brassica seed cake and sunflower oil significantly enhanced lipase production, yielding 9.04 ± 0.251 IU/mL after 48 h. RSM optimization achieved a maximum extracellular activity of 12.5 IU/mL. Scale-up in a stirred fermenter produced peak extracellular (26.43 ± 0.057 IU/mL) and intracellular (28.04 ± 0.041 IU/g) activities after 40 h, with maximum glucose utilization and biomass formation at 8 h and 24 h, respectively. The study successfully optimized lipase production from Aspergillus sojae using Brassica seed cake as a low-cost agro-industrial substrate, demonstrating both high yield and scalability.