Novel Nematocidal Compounds from Shrimp Shell Wastes Valorized by Bacillus velezensis RB.EK7 against Black Pepper Nematodes

Abstract

Among various organic wastes, shrimp shell powder (SSP) was the most suitable carbon/nitrogen source for producing antinematode compounds (ANCs) via Bacillus veleznesis RB.EK7 fermentation. The fermentation process for the enhancement of antinematode activity was investigated. B. veleznesis RB.EK7 produced the highest antinematode activity in the medium containing 0.8% SSP with an initial pH of 6.5–7.0, and fermentation was performed at 35–37 °C with a saking speed of 150 rpm for 72 h. Targeting ANCs were purified from the fermented culture broth and identified as thymine (1) and hexahydropyrrolo [1,2-a]pyrazine-1,4-dione (2) based on nuclear magnetic resonance (NMR) and mass spectra analysis and were compared to those of the reported compounds. Notably, for the first time, these compounds were found as novel ANCs. Thymine (1) demonstrated a potential nematicidal effect with near 100% mortality of second-stage juvenile (J2) nematodes and anti-egg hatching effects of 70.1%, while hexahydropyrrolo [1,2-a]pyrazine-1,4-dione showed moderate antinematode activities with 64.2% mortality of J2 nematodes and anti-egg hatching effects of 57.9%. The docking study coupled with experimental enzyme inhibition results indicated that the potent nematicidal effect of these compounds may be possibly due to the inhibition of the targeting enzyme acetylcholinesterase. The data of this study suggest that SSP can be potentially reused for the eco-friendly production of ANCs for the management of black pepper nematodes.

Enhancing Nematicidal Effect of Prodigiosin via Nano-Encapsulation Using Chitosan as a Novel Carrier Substance

“…To determine the possible action mechanism of Pg against root-knot nematodes, we evaluated the molecular mechanism of the nematicidal effect via docking study [23,[33][34][35][36]]. Among the protein targeting anti-root-knot nematodes, the enzyme AchE has been commonly used in virtual studies for the inhibition of nematode M. incognita, a major species of the genus Meloidogyne [23,34]. Therefore, this enzyme was also used as the targeting enzyme for the molecular docking in this work.…”

“…Molecular docking protocol: we assessed the molecular mechanism of anti-nematode activity of Pg released from E-Pg/CS NPs via virtual screening assays according to the method presented in detail in our previous work [23].…”

“…The novel anti-root-knot nematodes of Pg was recently reported in our previous study [11], however, its action mechanism has not been reported. To determine the possible action mechanism of Pg against root-knot nematodes, we evaluated the molecular mechanism of the nematicidal effect via docking study [23,[33][34][35][36]]. Among the protein targeting anti-root-knot nematodes, the enzyme AchE has been commonly used in virtual studies for the inhibition of nematode M. incognita, a major species of the genus Meloidogyne [23,34].…”

“…These two ligands are also bound to AChE with very low DS values of − 12.0 and − 10.4 kcal/mol, respectively, indicating that both cation-Pg and neutral-Pg appear to be possibly effective enzyme inhibitors of AChE. Some bioactive compounds isolated and identi ed from microbes with anti-AChE and anti-nematodes effect were also accessed through molecular docking (Table 7) and showing the inhibition e cacy with DS values in the range of -6.89 to -9.3 kcal/mol [23,39]. In this work, both forms of Pg show lower DS values (− 12.0 and − 10.4 kcal/mol), as such, Pg may be suggested as an effective anti-AChE inhibitor via docking study.…”

Emerging strategy for eco-friendly management of black pepper root-knot nematodes

“…Besides, the promising activity of prodigiosin might be associated with anti-acetylcholinesterase (AChE) -a common enzyme used to resist Meloidogyne nematode [67]. Compounds from Bacillus veleznesis RB.EK7 fermentation were identified as thymine and hexahydropyrrolo [1,2-a]pyrazine-1,4-dione [68]. These compounds were tested for anti-Meloidogyneincognita effect on black peppers.…”