Chitin and Lignin: Natural Ingredients from Waste Materials to Make Innovative and Healthy Products for Humans and Plant

Abstract

In a globalized world, plants are continually cut to obtain free land for intensive farming without remembering their important function in the planet ecosystem. They produce oxygen eliminating the carbon dioxide excess, contributing to reduce the pollution thus giving a great support to our health. According to the World Health Organization (WHO), air pollution -both outdoor and indoor- is nowadays "the biggest environmental risk to health carrying responsibility for about one in every nine deaths" (WHO, 2016). Outdoor pollution alone, in fact, kills around 3 million people each year. At this purpose however, it is necessary to remember that indoor emission of nanoparticles (NP) represent 50-80% of human exposure, calculated from 10.000 to 249.000 NP/mL air-while in polluted air NP are from ~10.000 to 50.000 NP/mL (Nohynek, 2011). Thus, there is a strict necessity "to consider air pollution as a global health priority in the sustainable development agenda" (WHO, 2016). Moreover, plants, multicellular organisms, as well as humans have evolved several mechanisms of defense and sensor systems to detect danger and prevent entry of most foreign material (Janeway et al, 2001). The sensors can direct and assist the host defenses by the use of specialized cells that ingest and digest foreign material. This protective non-specific method is called innate immune system, also connected with certain specific molecular patterns recognition associated with invading microbes or tissue damage (Nurnberger et al., 2004). In addition to innate immunity, vertebrates have evolved an adaptive immune system that relies on many antigen receptors, expressed by specialized immune cells. Unlike vertebrates, plants lack mobile defender cells and respond to infection by a two-branched immune system (Jones et al., 2006). The first branch recognizes and responds to all the common microbial molecules, while the second responds to pathogen virulence factors only. However, both plants and mammals have as first-line defense a barrier that, separating and shielding the interior of the body from the surrounding environment, represents the initial obstacle to be overcame from any pathogenic microorganisms. This barrier not only provides a physical separation, but releases also substances with antimicrobial properties. Moreover, when the first-line barrier has been breached, sensor systems are activated to give information to other components of the host defenses. Thus, while mammals activate, for example, the toll-like receptors capable to recognize families of compounds unique to microbes, plants release specialized compounds known as elicitors, signaling molecules able to induce their defense systems (Trouvelot et al., 2014). Examples of common ingredients, used from both plant and mammal as elicitors and defense-related compounds, are chitin and lignin. In this work, these materials will be briefly reviewed and results of chitin nanofibrils production and usage is reported. Finally, possible usage of combined chitin-lignin nanofibrils in commercial products will be pointed out.