Invasive plants in Western Europe as renewable raw materials for biorefining: the case study of Japanese knotweed

Abstract: Japanese knotweed (Fallopia japonica) is a non-native invasive freshwater plant commonly found in Western Europe, notably along water bodies. In Belgium, our group works on the identification of valuable option for the valorization of this plant in a biorefining perspective. Japanese knotweed is indeed a complex lignocellulosic plant composed of cellulose (about 35%), lignin (26%), hemicellulose (9%) and others (proteins, inorganics, secondary metabolites, etc.). The rhizome of the plant is also an attractive source of trans-resveratrol, a phenolic compound of
great potential for high added value applications for cosmetics or para-pharmaceutics.
Japanese knotweed is a complex heterogeneous matrix that requires pretreatment processes to individualize lignin from hemicellulose and cellulose for further valorization schemes. Many types of pretreatment allow such a fractionation, their efficiency depending on the structure and composition of the raw material, but mostly on the desired applications for the separated fractions. Our works have evidenced that a methodology combining solvents mixture and Brönsted acid could be a cost-effective option for the one-step recovery of almost all the valuable compounds found in the Japanese knotweed and for their subsequent valorization for niche markets. This pretreatment methodology was found particularly suited for the extraction of phenolic compounds (in particular
resveratrol) in high yields and purity.
This contribution highlights the innovative applications of molecules extracted from an invasive plant and the benefits of this strategy in biorefining options. Valorization of secondary metabolites, production of high added value derivatives of lignin and cellulose are herein presented and llustrated.