A new source of bacterial myrosinase isolated from endophytic Bacillus sp. NGB-B10, and its relevance in biological control activity

Abstract

Plant metabolism interacts strongly with the plant microbiome. Glucosinolates, secondary metabolites synthesized by Brassica plants, are hydrolyzed by myrosinase into bioactive compounds of great importance in human health and plant protection. 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 identified. Response surface methodology (RSM) was applied to statistically optimize culture conditions for myrosinase production from Bacillus sp. strain NGB-B10. The Plackett–Burman design indicated that nitrogen concentration, incubation period, and agitation speed were the significant 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 purified 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 purified 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 affords an optimized method to enhance myrosinase production.

Beyond defense: Glucosinolate structural diversity shapes recruitment of a metabolic network of leaf-associated bacteria

“…In addition, this hydrolysis reaction releases sulfate (S), and the further metabolism of breakdown products could provide more carbon or nitrogen in the form of amines. Supporting nutritive roles, human gut bacteria break down GLSs ( 44 ), and myrosinase-producing bacteria have been identified in both soil and plant roots ( 45 , 46 ) as well as in the phyllosphere ( 47 ). GLSs as resources are costly, however, since myrosinase cleavage also releases an aglycone that can rearrange to form ITCs or other toxic products.…”

“…Assuming this enrichment is indeed due to GLS metabolism, it is possible that bacteria that can access GLSs do not need to be present in high abundances so that we did not detect Yersiniaceae. On the other hand, many bacteria can utilize GLSs (often other Enterobacterales) ( 46 ) and myrosinases have been suggested to be enriched in the phyllosphere ( 47 ). Given the differing specificities of myrosinases and ITC hydrolases for substrate structures, it is very likely that other bacteria may be able to functionally replace Yersiniaceae in planta , preventing its consistent enrichment in the phyllosphere.…”

Effects of pulsed electric field technology on the nutritional value and biological function of plant food

“…Thioglucoside is widely used in the pharmaceutical and food industries for its antibacterial, neuroprotective, and anticancer effects (Watson et al, 2013;Choudhury et al, 2022;Hoffmann et al, 2022;Marcinkowska and Jelen, 2022;Youseif et al, 2022;Zhou et al, 2022). Thioglucoside is water-soluble and heat-sensitive; therefore, heating causes a large loss of thioglucosides, and heat treatment should be avoided when extracting these components (Hoffmann et al, 2022;Marcinkowska and Jelen, 2022).…”