Vijitra Luang-In, Abdulhadi Ali Albaser and John T. Rossiter

DOI: 10.14456/sjst-psu.2020.69

pp. 549 - 563

Abstract

A recombinant β-glucosidase human gut bacterium capable of nitrile production from desulfo-glucosinolates was
studied. The bgl4 gene (2,151 bp) from Enterococcus casseliflavus CP1 was cloned and overexpressed in Escherichia coli
BL21(DE3) at 25 °C for 16 h in LB medium using 0.5 mM isopropyl β-D-1-thiogalactopyranoside inducer. The recombinant
bgl4 enzyme (79 kDa) was purified using Ni²⁺ affinity column chromatography. This recombinant bgl4 enzyme of the glycosyl
hydrolase 3 family did not degrade glucosinolates; however, it transformed desulfo-glucosinolates, except for desulfoglucoraphanin, to produce the corresponding pure nitriles in citrate phosphate buffer pH 7.0 and LB medium. The bgl4 enzyme
activity toward pNPG in buffer was optimal at pH 7.0 and 37 °C at 23.4 U/mg, and promoted by Mn²⁺; however, activity was
slightly deactivated by Fe²⁺. This provided a possible alternative metabolic route involving nitrile formation from desulfoglucosinolates by β-glucosidase in certain bacteria.

Keywords

• β-O-glucosidase
• desulfo-glucosinolate
• enterococcus
• glycosyl hydrolase
• nitrile