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. Electronic supplementary material The online version of this article (10.1186/s13068-019-1530-8) contains supplementary material, which is available to authorized users.

Mechanisms of Insecticidal Action of Metarhizium anisopliae on Adult Japanese Pine Sawyer Beetles (Monochamus alternatus)

“…JPS adults overexpressed actin and tropomyosin for muscle contraction as a defense mechanism. 1 The mechanism underlying the insecticidal effect of spraying conidia of M. anisopliae JEF-279 was similar to that observed for the treatment with destruxins or protease. Heat shock protein 70 (HSP70) contributes to insect survival under stress conditions by promoting protein integrity and cell homeostasis.…”

“… 19 In a previous study, spraying insecticidal secondary metabolites (destruxins at 336 ppm and protease at 85 μg) on JPS adults resulted in 100% insect mortality after 5 days. 1 …”

“…PWD is caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus Nickle (Aphelenchida: Aphelenchoididae) and results in severe environmental and economic damages in Asia (Korea, China, Japan, and Taiwan), Europe (Spain and Portugal), and North America (the United States of America, Canada, and Mexico). 1 , 2 Needles initially decolorize, then turn brown, and eventually die in several months. 3 Generally, browning of plants is strongly influenced by polyphenol oxidase, which induces the oxidation of phenolic compounds during the cellular disorganization.…”

“…g ., destruxins and protease-containing culture filtrate produced by M. anisopliae JEF-279, showed insect pathogenicity against JPS adults. 1 However, the insecticidal mechanism of action when M. anisopliae JEF-279 conidia are sprayed on JPS adults remains unknown.…”

Breeding Targets to Improve Biomass Quality in Miscanthus

“…Total uronic acid contents, including both galacturonic and glucuronic acid, have been reported to be 1.2% ( w / w ) of raw biomass and 1.8% ( w / w ) of total polysaccharide content [ 185 , 186 ]. Reported rhamnose levels in miscanthus have usually been very low (<0.30% w / w ) [ 122 , 134 , 140 ] or even undetectable [ 187 , 188 ]. In other studies, total pectin levels (0.5–3.5% w / w ) have been expressed as percentage of cell wall extracted with ammonium oxalate [ 140 , 187 ].…”