Pyroligneous Acids of Differently Pretreated Hybrid Aspen Biomass: Herbicide and Fungicide Performance

Abstract

The pyroligneous acids (PAs) of woody biomass produced by torrefaction have pesticidal properties. Thus, PAs are potential alternatives to synthetic plant protection chemicals. Although woody biomass is a renewable feedstock, its use must be efficient. The efficiency of biomass utilization can be improved by applying a cascading use principle. This study is novel because we evaluate for the first time the pesticidal potential of PAs derived from the bark of hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) and examine simultaneously how the production of the PAs can be interlinked with the cascade processing of hybrid aspen biomass. Hybrid aspen bark contains valuable extractives that can be separated before the hemicellulose is thermochemically converted into plant protection chemicals. We developed a cascade processing scheme, where these extractives were first extracted from the bark with hot water (HWE) or with hot water and alkaline alcohol (HWE+AAE) prior to their conversion into PAs by torrefaction. The herbicidal performance of PAs was tested using Brassica rapa as the test species, and the fungicidal performance was proven using Fusarium culmorum. The pesticidal activities were compared to those of the PAs of debarked wood and of commercial pesticides. According to the results, extractives can be separated from the bark without overtly diminishing the weed and fungal growth inhibitor performance of the produced PAs. The HWE of the bark before its conversion into PAs appeared to have an enhancing effect on the herbicidal activity. In contrast, HWE+AAE lowered the growth inhibition performance of PAs against both the weeds and fungi. This study shows that hybrid aspen is a viable feedstock for the production of herbicidal and fungicidal active chemicals, and it is possible to utilize biomass according to the cascading use principle.

Hormetic Effect of Pyroligneous Acids on Conjugative Transfer of Plasmid-mediated Multi-antibiotic Resistance Genes within Bacterial Genus

“…40 The effects were consistent with that of PA, which is mainly explained by the complex compositions of dissolved biochars such as humic acid-like substances, small molecule phenols, and organic acids. PAs, one of the by-products simultaneously derived from ACS Environmental Au biomass pyrolysis for biochar production, 28,29 containing similar chemical components with the dissolved biochars (Figure S1), would be responsible for the hormesis on ARG transfer, which will be discussed in the following section.…”

“…Increasing strategies are recommended to alleviate ARG pollution in agricultural soils, such as aerobic composting or anaerobic digestion of manure and sludge before use, , inactivation of ARGs and antibiotic resistant bacteria from the reclaimed water before irrigation, vermiculture, , phage therapy, and soil amendment (e.g., biochar, calcined eggshell, and nanomaterials) applications. ,, Among them, soil amendments, , which may fight against ARGs already existing in soils, have attracted increasing attention because of their efficiencies and convenient implementation . Pyroligneous acids (PAs) derived from biomass pyrolysis, as multifunctional soil amendments with long history, can decrease soil salinity and pH, , regulate bacterial community, kill plant pathogenic fungi and bacteria, − and promote crop growth and grain yield . Our recent studies first demonstrated that PA amendment can reduce ARG levels in soils grown with vegetable Brassica, regardless individual application or combined with biochar amendment. , Similarly, another research also reported that the combined treatment of bamboo biochar and distilled PA showed significant synergistic effects on alleviating ARG proliferation in municipal solid waste composts .…”

“…These studies mainly ascribed the decreased ARG abundances to the inhibited HGT, reduced co-selection of heavy metals and lowered potential host bacteria of ARGs but ignored the underlying mechanisms of PA on HGT process. Previous studies have verified that PA as a bacteriostatic agent can damage the cell structure and inhibit the bacterial energy production and cell metabolic activity, − which may impede the conjugative process. However, these potential effects and the relevant mechanisms underlying HGT process by PA amendment remain unclear, limiting the further development of the PA-based technology to abating soil ARG pollution.…”

“…The potential mechanisms include the overproduced reactive oxygen species (ROS), enhanced membrane permeability, promoted cell-to-cell contact by stimulating extracellular polymeric substance (EPS) production and decreasing electrostatic repulsion between cell surfaces, induced SOS response, and regulated conjugation-related gene expression. − On the contrary, these antibiotics and non-antibiotic chemicals , at inhibitory levels (above the MIC) generally inhibited ARG conjugation by strong bacteriostasis. As common soil amendments, PAs containing a large variety of water-soluble compounds (e.g., 39–124 species) such as organic acids, phenolics, esters, aldehydes, and alcohols , can effectively inactivate bacteria, fungi, plant pathogens, and viruses . A study reported that a PA obtained by slow pyrolysis of a mixture of pine, spruce, and fir wood particles, containing organic acids such as acetic acid and aldehydes like vanillin and furfural, all of which are known as microbial inhibitors, showed antibacterial activity against five pathogenic bacterial strains .…”

“… 10 , 22 , 23 Among them, soil amendments, 22 , 23 which may fight against ARGs already existing in soils, have attracted increasing attention because of their efficiencies and convenient implementation. 23 Pyroligneous acids (PAs) derived from biomass pyrolysis, as multifunctional soil amendments with long history, can decrease soil salinity and pH, 24 , 25 regulate bacterial community, 24 kill plant pathogenic fungi and bacteria, 26 − 28 and promote crop growth and grain yield. 25 Our recent studies first demonstrated that PA amendment can reduce ARG levels in soils grown with vegetable Brassica , regardless individual application or combined with biochar amendment.…”