Abstract:
Plant metabolism interacts strongly with the plant microbiome. Glucosinolates, secondary metabolites synthesized by Bras-
sica plants, are hydrolyzed by myrosinase into bioactive compounds of great importance in human health and plant protec-
tion. Compared with myrosinase from plant sources, myrosinase enzymes of microbial origin have not been extensively
investigated. Therefore, seven endophytic strains corresponding to Bacillus sp. were isolated from Eruca vesicaria ssp. sativa
plants that could hydrolyse glucosinolates (sinigrin) in the culture medium and showed myrosinase activity (0.08–19.92 U
mL−1). The bglA myrosinase-related gene encoding the 6-phospho-β-glucosidase (GH 1) from Bacillus sp. NGB-B10, the
most active myrosinase-producing bacterium, was successfully identifed. Response surface methodology (RSM) was applied
to statistically optimize culture conditions for myrosinase production from Bacillus sp. strain NGB-B10. The Plackett–Bur-
man design indicated that nitrogen concentration, incubation period, and agitation speed were the signifcant parameters in
myrosinase production. The application of the Box–Behnken design of RSM resulted in a 10.03-fold increase in enzyme
activity as compared to the non-optimized culture conditions. The myrosinase was partially purifed by 40% fractionation
followed by SDS-PAGE analysis which yielded two subunits that had a molecular weight of 38.6 and 35.0 KDa. The puri-
fed enzyme was stable under a broad range of pH (5.5–10) and temperatures (10–65 °C). The hydrolysis products released
by bacterial myrosinase from some glucosinolate extracts had higher and/or equivalent in vitro antagonistic activity against
several phytopathogenic fungi compared to the nystatin (a broad-spectrum antifungal agent). This study provides original
information about a new source of bacterial myrosinase and afords an optimized method to enhance myrosinase production.
