# NMR and LC-MS-Based Metabolomics to Study the Effect of Surfactin on the Metabolome of Flax
## 1 Introduction  
Fax, also known as _Linum usitatssimum_ (Linaceae), is a multipurpose plant used for its fiber and nutritious seeds. It grows until 0.9 to 1.2 m tall, with thin stalks, short lance-shaped leaves, and blooms with five petals in a variety of hues. The fruits are little capsules with glossy brown seeds accumulating high contents of omega-3 fatty acids and lignans. Flax has been domesticated for almost 8000 years, beginning in the Fertile Crescent region [1]. Fax fiber, one of the earliest textile fibers known to humans, is produced by processes such as retting, drying, crushing, and beating. Its strength, durability, and moisture absorption make it ideal for a wide range of items, including delicate linen textiles and industrial materials such as canvas, twine, and fire hoses. Linen clothing is popular because it keeps the user cool and is resistant to microbes [2]. Linen culture for fiber production is mainly found in northwestern Europe [1, 3]. Faxseed contains omega-3 fatty acids, lignans, dietary fiber, protein, and minerals. It can be eaten raw or roasted; mixed into salads or baked items; or extracted to make linseedoil for paints, varnishes, and supplements. Flax culture for seed production is mainly found in nations such as Russia, Kazakhstan, Canada, and China [4]. Genetic research, combined with advances in genomics and metabolomics, allows for improvement in flax culture and applications [5]. Because flax culture can be damaged by several biotic or abiotic stresses, it is interesting to develop new practices to limit the use of chemical products that potentially damage the environment and health. The use of biostimulants and biocontrol agents has economic potential in agriculture because they can increase production, reduce input costs, and promote sustainable agricultural practices [6]. They can improve yields, reduce dependency on chemical pesticides, and promote global food security. Importantly, they can be economically competitive with traditional ways, promoting their inclusion into contemporary agricultural systems. These products may be derived from natural microbes or plants. As a result, they can decrease or eliminate damage caused by certain pests and diseases while also improving plant performance [7; 8; 9]. Among these agents, _Bacillus_ strains are available in different commercial products. These bacteria produce several metabolites, belonging to the lipoprotein family, which can induce plant resistance to different pathogens. A study on surfactin produced by _Bacillus subtilis SF1_ against the fungal agent _Fusarium foetens_, which causes potato wilt, has shown that surfactin and other lipopeptides produced by _Bacillus_ may have biocontrol properties against plant diseases [10]. Surfactant molecules have also been recognized as powerful biostimulants in agricultural and horticultural systems due to their ability to solubilize large organic molecules and increase their availability for uptake by plants [11]. Surfactant is a cyclic lipopeptide biosurfactant. Its structure consists of a circular heptapeptide containing specific amino acids such as L-leucine, D-leucine, L-valine, L-aspartate, and L-glutamate, along with a long-chain fatty acid [11; 12]. Surfactant has a variety of uses in plant protection and has been proven to trigger induced systemic resistance (ISR) in plants, thus increasing their pathogen defense systems [13]. For example, surfactin has been shown to activate ISR in plants such as tobacco and tomato. Furthermore, surfactin has been shown to improve resistance to diseases such as cucurbi powdery mildew in melon plants. These findings emphasize surfactin's potential as a biocontrol agent in agriculture, promoting plant health and disease management [13; 14]. Surfactant has also been shown to boost the host's defensive capabilities [15]. Additionally, surfactin has been found to increase the uptake of certain minerals and nutrients, which in turn may influence plant metabolism.