Efficient transformation of grease to biodiesel using highly active and easily recyclable magnetic nanobiocatalyst aggregates

[Display omitted] ► New method for converting grease to biodiesel using nanobiocatalyst is reported. ► Active and separable magnetic nanobiocatalyst aggregates (MNA) are engineered. ► Transforming grease to biodiesel with MNA TL (3.3wt.%) gives 99% yield in 12h. ► MNA TL is stable and recyclable, retaining 88% productivity in the 11th cycle. ► Esterification of FFA in grease with MNA CA (0.45wt.%) is high yielding (>97%). Green and efficient production of biodiesel (FAME) from waste grease containing high amount of free fatty acid (FFA) was achieved by using novel magnetic nanobiocatalyst aggregates (MNA). Thermomyces lanuginosus Lipase (TLL) and Candida antartica Lipase B (CALB) were covalently immobilized on core–shell structured iron oxide magnetic nanoparticle (80nm), respectively, followed by freeze-dry to give MNA (13–17μm) with high yield (80–89%) and high enzyme loading (61mg TLL or 22mg CALB per gram MNA). MNA TL showed the best performance among immobilized enzymes known thus for the production of FAME from grease (17wt.% FFA) with methanol, giving 99% yield in 12h (3.3wt.% catalyst). MNA TL was easily separated under magnetic field and reused, retaining 88% productivity in 11th cycle. MNA CA converted >97% FFA in grease (17wt.% FFA) to FAME in 12h (0.45wt.% catalyst), being useful in two-step transformation of grease to biodiesel.