*3.8. β-Glucuronidase Activity*

Determination of β-glucuronidase (EC 3.2.1.31) was based on the Kapnoor and Mulimani methodology [88]. The test was prepared by withdrawing from the bioreactor 200 µL of the contents, to which phosphate buffer (pH 7.0) and NaCl (0.1 M) were added. The samples were shaken for 1 h, then centrifuged to give the supernatant. Then, 200 mL substrate (1 mg/mL β-glucuronidase suspended in phosphate buffer, pH 6.7) was added to 200 mL of the supernatant, and incubated for 2.5 h at 40 ◦C. The reaction was stopped with sodium carbonate. The absorbance was measured at 420 nm. The total content of β-glucuronidase was expressed as mM/g of nitrogen soluble.
