Green synthesis and effective genistein production by fungal β-glucosidase immobilized on Al 2 O 3 nanocrystals synthesized in Cajanus cajan L. (Millsp.) leaf extracts

The research deals with the isoflavone genistein production, followed by the β-glucosidase production from Aspergillus oryzae. The Cajanus cajan leaf extract was prepared and the optimized extraction parameters were leaf powder weight (1 g), agitation time (75 min), and temperature (60°C). The optimal conditions for β-glucosidase production by submerged fermentation were 0.4% (w/v) (NH 4 ) 2 SO 4 as nitrogen source, 0.05% (w/v) MgSO 4 as magnesium source, 2 ml (v/v) size of inoculum, and 60 min incubation time. The Al 2 O 3 nanocrystals (NCs) were synthesized by optimal volume of leaf extract (25 ml) and procurement period (50 min) along with Al 2 NO 3 and NaOH. The β-glucosidase immobilization on Al 2 O 3 NCs improved the specific activity from 2.38 ± 0.002 to 5.64 ± 0.07 U·mg −1 . The maximum genistein production was achieved with the rate of biotransformation (48 h) and enzyme concentration (1% (v/v)) along with the substrate level. In fourier transform infrared spectroscopy analysis, the difference between both β-glucosidases free and Al 2 O 3 immobilized was obtained with peaks at 1,120 and 2,150 cm −1 . The X-ray diffraction analysis for the NCs was obtained from 10° to 80° with several intensities. and zeta potential size distribution was recorded at 16.2% of intensity with 206.4 d nm. After immobilization, the stability of the β-glucosidase was increased, thereby increasing its potential in the pharmaceutical, biofuel, food, and beverage industries.