Insecticidal and anti-microbial activity of bio-oil derived from fast pyrolysis of lignin, cellulose, and hemicellulose

Conflicting views regarding synthetic pesticides include the successful use as pest management tools for agriculture and forestry on one hand and the threats to components in the environment. Likewise, the residues from agriculture and forestry create a waste disposal problem, but are a potential bio-resource to be profited from. This abundant biomass can be converted into bio-fuel and valuable products (e.g., biopesticides) through thermochemical process and provide a potential solution to two problems. The objective of this study was to pyrolyze lignin, cellulose, and hemicellulose plant biomass individually for the separation and identification of pesticide compounds. The biomasses were individually pyrolyzed at 450 and 550 °C in a fluidized bed reactor and the bio-oil was collected from the condenser and electrostatic precipitator (ESP). Lignin ESP bio-oil was the most toxic at both temperatures based on bioassays using (1) insects (Leptinotarsa decemlineata, Trichoplusia ni, and Acyrthosiphon pisum); (2) fungi (Pythium ultimum, Rhizoctonia solani, and Sclerotinia sclerotiorum); and (3) bacteria (Clavibacter michiganensis subsp. michiganensis, Streptomyces scabies, and Xanthomonas campestris pv. vesicatoria). The lignin ESP organic phase retained the insecticidal activity and fractionation by semi-preparative high performance liquid chromatography (HPLC) isolated further the activity. Analyses of these fractions by gas chromatography–mass spectrometry (GC–MS) identified several polycyclic aromatic hydrocarbons (PAHs) potentially contributing to the pesticidal activity, including anthracene, pyrene, phenanthrene, fluoranthene, benzoanthracene, 1-phenylnaphthalene, 1-methylphenanthrene, 2-phenylnaphthalene, and 4,5-methylenephenanthrene. In light of the present study, it may be concluded that lignin is a very promising source of biopesticides when the reactor operating conditions are optimized.