Chitin & Chitosan Production

What is Chitin & Chitosan?

Chitosan is a sugar (linear polysaccharide) composed of deacetylated beta-1,4-D-glucosamine which is deacetylated form of chitin. Literally, chitosan has a degree of deacetylation (DD%) >50% which is obtained after deacetylation stage. Chitin, as a second abundant natural polysaccharide after cellulose, is a main component of exoskeletons of arthropods, the cell walls of fungi, insects, and etc (Table 1). Chitin has 3 polymorphic forms including α- (anti-parallel, most abundant, highly crystalline, strong H-bonding insoluble), β- (parallel, weak H-bounding, unstable, water soluble), and γ-chitin (mixture of α and β).
The chemical structure of chitin consists of repeating Glucosamines linked with a glycosidic oxygen (O-glycosides); glucose part in chitin have an amyl group linked (NHCOCH$_{3}$ or N-acetyl group) -instead of a hydroxyl group (OH) in cellulose- that consists of carbon (C) and nitrogen (N) atoms. Nitrogen has an electrically positive charge, while the oxygen (double bonded to the N-acetyl group) is electrically negative. Referring to electromagnetic courses, this two separate but spatially close enough atoms can be interpreted as a dipole in the molecule, which increases the hydrogen bond's possibilities which is formed between molecules. When we mix chitin solution with a composite-matrix consisting of various compounds, the resulting structure can be mechanically hard because of all the weak interactions between neighbor molecules. Naturally, chitin is insoluble in water and after deacetylation phase, the chitosan has acid solubility properties thus various modified chitosan methods are conducted to modify primary/secondary hydroxy and primary amino functional groups (remove, charge change, quaternization, substitution) through temperature, pH (protonation), hydrolysis, surface modification with free radicals/cold Plasma and etc.

Table 1. Chitin content in common sources

Brief timeline

• 1811 Chitin discovery by Prof. Henri Braconnot ("Fungine" isolation from mushroom)
• 1823 Chitin term from "chiton" by Antoine Odier, beetle cuticles study
• 1838 Cellulose discovery
• 1859 Chitosan discovery by Rought
• 1920s Chitin fibers production
• 1930s Synthetic fibers appears
• 1950s Chitin & Chitosan chemical structure studies by X-ray diffraction, IR-Spectroscopy, and enzymic analysis
• 1970s Chitin & Chitosan gain interest
• 1977 1st international conference about chitin & chitosan

Chitosan Oligosaccharide (COS)

COS is an oligomer of β-(1➔4)-linked d-glucosamine which can be synthesized using chitosan degradation (acidic, enzymatic, oxidative, and radiation). thus, COS has low molecular weight (~<2kDa), higher DD%, enhanced degree of polymerization (DP), and water solubility which can be absorbed in intestine or excreted with the urine. With lower electronegativity of N-atoms, amino groups has greater nucleophilic properties. Cationic COS can interact electrostatically with negatively charged entities like cell membranes (permeability change, disruption and etc.). COS shows better blood-brain barrier (BBB) penetration ability (Alzheimer's disease (AD) treatment candidate).

Chitin & Chitosan Extraction

According to literature, chitosan has vast applications (Table 2) due to incredible properties (Non-toxic, biodegradable, biocompatible, cytocompatible, anti-microbial, anti-cholestrolemic, anti-oxidant, anti-inflamatory, analgestic, hemostatic activities, mucoadhesion, angiogenesis stimulatory, macrophase activation, adsorption enhancer) [1].

Table 2. Chitosan applications

Chemical Extraction

Technically, the chitin source get through various stages as separation (washing, Crashing/Grinding), purification (deproteinization, demineralization, decolorization), deacetylation, degradation. For example, shrimp gets purchased, shrimp shell gets separated, washed by hot water, grinned to get desired particles (by considering filtering No.), deproteinized (also lipid removing) by alkali solution (~5% NaOH or KOH + Heat), demineralized (CaCO$_{3}$, ... removing) by acidic solutions (e.g. ~ 30%HCl or equivalent H$_{2}$SO$_{4}$, acetic acid), decolorized by oxidation (H$_{2}$O$_{2}$), deacetylated by alkali solution (stronger NaOH + heat (for faster results)), degraded by various techniques to get COS.
Extraction route depends on source and final market applications; for example in fungal mycelium, the processed are 10% NaOH, acetic acid, glucanases, 50% NaOH to get our final gel which after 10% NaOH, solubilized proteins, lipids, pigments and hemicelluloses get washed out.

Biological Extraction

Using microbes and enzymes.

Novel Extraction methods

1) microwave-assisted extraction (MWAE)
2) ultrasound-assisted extraction (UAE)
3) ultrasound-microwave extraction (UMWE)
4) green reaction solvents (e.g. glycerol)
5) ...

What we are trying to do!

We are gathering information about green and natural products for pollution lowering and easing industrial processes by innovating and inventing novel techniques, machines and products. Here, we are trying to build a production line according to our issuing patent for stable commercial link stablishing. In this case, we've focused on :
1) Biomedical Grade chitosan synthesis
2) High Extraction rate
3) Lowering Time, Cost, chemical & energy consumption, stages, complexity, ...
4) Chitin & Chitosan products
5) Industrial-level production line
6) Cold Plasma COS synthesis for nano-therapeutic applications
7) Marine resource management & recycling

Contributors

Inv. Ali Bakhshi, Ali Jamali

Project’s page in ResearchGate.