Advanced strategy to produce insecticidal destruxins from lignocellulosic biomass Miscanthus

Abstract

Background: Biorefineries are widely recognized as the most feasible solution to the problem of achieving environmental sustainability along with economic growth. Furthermore, pine wilt disease has caused severe environmental and economic damage worldwide to date. Herein, a highly efficient, advanced process for producing destruxins (DTXs) from Miscanthus (MCT) is reported, along with an application strategy. Results: The acetic acid-sodium chlorite pretreatment of MCT (AASC-MCT) is found to improve the monosaccharide production. Through biocatalytic conversion processes (simultaneous saccharification and cultivation), Metarhizium anisopliae JEF-279 can efficiently produce DTXs from 1% (w/v) AASC-MCT, i.e., DTX E (334.8 mg/L), A (288.8 mg/L), and B (48.6 mg/L). Monochamus alternatus (MA, Japanese pine sawyer) is known to act as a mediator transferring Bursaphelenchus xylophilus to pinewood. As B. xylophilus is associated with the occurrence of pine wilt disease, biological control of MA is a major strategy or controlling this disease. In this study, upon the application of a mixture of DTXs and protease-containing culture filtrate (PCF), complete mortality of MA is observed after a 5-day incubation. The MA immune system response is believed to cause an overexpression of actin and tropomyosin as a defense mechanism against the flaccid paralysis induced by the DTXs and PCF treatment. Conclusions: These results suggest that MCT can be used as a major feedstock in the biorefinery industry and that DTXs can be applied as an insecticide for biological control of pine wilt disease via MA termination.