Bioconversion of mustard oil cake for production of lipase, optimization and direct immobilization from solid-state fermentation extract

Fungal lipases are the leading industrial biocatalyst due to their broad applications, but high cost limits their commercial usage. The low-cost agri-residues substrates can reduce the cost of lipase production. However, the compatibility of agri-residue with fungal species, recovery process of lipase and stability of the enzyme are crucial steps. The aim of the present work was optimization of lipase production from a suitable combination of fungal culture with a locally available vegetable oilseed cake (mustard/groundnut/almond/cottonseed) in solid-state fermentation process and its direct immobilization. The enzyme produced using selected combination of <i>Rhizopus oryzae</i> and mustard oilseed cake was optimized by Plackett–Burman design, one-factor-at-a-time and central composite design (CCD). The highest enzyme activity of 25.08 U/gds was obtained by CCD at urea 2.11% w/w, inoculum size 1.18% v/w, and moisture content 69.99% w/w. The crude enzyme from the extract was immobilized on functionalized magnetic nanoparticles with the results of protein loading 68.88 ± 3.54 µg/mg of MNPs and activity recovery of 60.33 ± 3.03%. This study can be helpful to explore the suitability of locally available agri-residue for production of lipase and utilization of enzyme in different industrial applications.