Green synthesis and effective genistein production by fungal β-glucosidase immobilized on Al2O3 nanocrystals synthesized in Cajanus cajan L. (Millsp.) leaf extracts

Abstract

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) (NH4)2SO4 as nitrogen source, 0.05% (w/v) MgSO4 as magnesium source, 2 ml (v/v) size of inoculum, and 60 min incubation time. The Al2O3 nanocrystals (NCs) were synthesized by optimal volume of leaf extract (25 ml) and procurement period (50 min) along with Al2NO3 and NaOH. The β-glucosidase immobilization on Al2O3 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 Al2O3 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.

Keywords

• genistein
• biotransformation
• cajanus cajan
• submerged fermentation
• uv–visible spectra
• fourier transform infrared spectra