Abstract: Lipases are biocatalysts of great industrial and agricultural importance. The production of lipase by microbial sources can be optimized by adjusting the physicochemical and nutritional parameters. The aim of the present study was to determine the optimal production of extracellular lipase by Aspergillus flavus in solid-state fermentation and to evaluate its impact on lipid mobilization and seed germination in Brassica napus. A. flavus, a morphologically identified and molecularly confirmed strain, was initially isolated from oil-roasted bread and cultured on malt extract agar for enzyme production under solid-state fermentation. Optimization of fermentation parameters, including incubation time, temperature, pH, inoculum type and size, substrate type and concentration, and supplementation with metal ions, carbon, oil, and nitrogen sources, was performed using the one-variable-at-a-time (OVAT) approach as a preliminary optimization method. Lipase activity was determined by a titrimetric method using an olive oil emulsion. The optimized enzyme extract was applied to B. napus seeds to assess its effects on germination, seedling growth, and lipid mobilization. The optimal conditions were 48 h incubation, 40 °C, pH 8, spore inoculum (1 mL), 20 g Nigella meal, 2 % (w/v) CdCl2, 3 % (w/v) fructose, 3 % (v/v) mustard oil, 2 % (w/v) ammonium sulfate, and 1 % (w/v) yeast extract, resulting in maximum extracellular lipase activity (14.99 ± 1.66 U mL-1). Application of the optimized lipase significantly improved germination, radicle length, seedling fresh weight, and free fatty acid content by 12.8 %, 31.4 %, 16.4 %, and 50.4 %, respectively (p ≤ 0.05) compared to the control, indicating enhanced lipid mobilization and seed vigor. These findings demonstrate the potential of fungal lipase in industrial production and agricultural applications, particularly in improving seed germination and early seedling development.
Bashir et al. (Thu,) studied this question.