2.4 Enzyme purification
The culture supernatant was filtered with 0.45 μm filters before being loaded on the column. Purification of the rAGL was performed with the AKTA Prime Plus (GEHealthcare Bio-science, Uppsala, Sweden) using a 5-mL high affinity Ni-Charged resin FF prepacked column (Genscript, Nanjing, China) [44]. After exchanging with sodium acetate buffer (100 mM, pH 4.0) and concentrated using an Amicon® Ultra-15 Centrifugal Filter Unit with an Ultracel-30 membrane (Merck Millipore Ltd., Ireland), the elute solution containing AGL was collected and stored at 4 °C for further experiments. The molecular weight of rAGL and protein purity were determined by 8% (w/v) SDS-PAGE. The protein concentration was determined using the Bradford method [45].