EP3976662A1

EP3976662A1 - A method for producing chitosan

Info

Publication number: EP3976662A1
Application number: EP19931347.9A
Authority: EP
Inventors: Ahmet Cemal SAYDAM
Original assignee: Chitlig Enerji Uretim Ve Pazarlama AS
Current assignee: Chitlig Enerji Uretim Ve Pazarlama AS
Priority date: 2019-05-28
Filing date: 2019-05-28
Publication date: 2022-04-06
Also published as: EP3976662A4; WO2020242396A1

Abstract

The present invention relates to a method for producing chitosan. The method allows the utilization of desert soil. The said soil is reacted with oxalic acid, and chitosan is formed. Obtaining combustible gases using the method disclosed in the present invention removes the need for using bases. Thus, it is more environment-friendly compared to other methods.

Description

A METHOD FOR PRODUCING CHITOSAN Technical Field

The present invention relates to a method for producing chitosan from chitin especially using chitin containing shale rocks, desert soil, and/or crustaceans. Background of the Invention

By definition, chitosan is a chitin molecule refined from its acetyl groups. Chitin is the second most abundant biopolymer found on earth next to cellulose and is a long chain polymer of N-acetylglucosamine. Chitin is present in the exoskeletons of crustaceans and also in the cell walls of fungi and insects, especially arthropods, spiders and crustaceans. Chitosan is a collective name representing a family of de- N-acetylated chitins deacetylated to different degrees. Both chitin/chitosan and their modified derivatives find extensive applications in medicine, agriculture, food, and non-food industries as well. They have emerged as a new class of physiological materials of highly sophisticated functions. Their application versatility is a great challenge to the scientific community and to industry. All these are the result of their versatile biological activity, excellent biocompatibility, and complete biodegradability in combination with low toxicity In the state of the art, it is obtained from crustaceans. The proteins and the methyl groups in the chitin forming the shells of the crustaceans are removed, using acids and strong bases, and thus chitosan is obtained. Another way of obtaining chitosan is using specific fungi. However, all of the known methods involve using the shells of the crustaceans or fungus as a source of chitin, a precursor for chitosan. An alternative means for producing chitosan is needed.

The production methods of chitin in the state of the art requires treating the chitin source with a base such as sodium hydroxide or potassium hydroxide. This increases the number of process steps, and the number of materials required for obtaining chitosan, thus increasing the cost, and the environmental impact of the said production. A cost-effective and environmentally friendly production method is needed.

The Chinese patent document numbered CN103113496 in the background of the invention relates to production of chitosan. In the said document, the production of chitosan requires wastes generated in aquatic product processing, and treating these wastes with sodium hydroxide.

The United States patent document numbered US20130331557 in the background of the invention relates to a chitosan manufacturing process. In the said process, chitin-containing raw material is demineralized using a hydrochloric acid solution, and then deproteinized using a sodium hydroxide solution.

None of the documents in the state of the art disclose a method for obtaining chitosan using any materials other than crustacean shells, and none of the said documents present a production method as in the inventive method.

Summary of the Invention

The object of the invention is to provide a method for producing chitosan.

Another object of the invention is to provide a method for producing chitosan utilizing alternative raw materials. Brief Description of the Drawings

The following figures provided as supportive evidences for chitosan produced by using Saharan soil:

Figure 1. SEM image of the chitosan obtained by the inventive method, at x 10000 magnification

Figure 2. SEM image of the chitosan obtained by the inventive method, at x20000 magnification

Figure 3. SEM image of the chitosan obtained by the inventive method, at x80000 magnification

Figure 4. Another SEM image of the chitosan obtained by the inventive method, at x80000 magnification

Figure 5. FTIR Spectrometry results of the chitosan obtained by the inventive method

Detailed Description of the Invention The inventive method of producing chitosan comprises the steps of;

- providing at least one component comprising chitin,

- milling a component to obtain a milled component,

- solubilizing the milled component,

- separating the supernatant,

- reacting the supernatant with an oxalic acid solution,

- separating the liquid phase,

- introducing a base thereby precipitating chitosan,

- separating the precipitated chitosan thereby obtaining chitosan. In the inventive method, Saharan soil is especially preferred as the component comprising chitin. However, any component comprising chitin is suitable to be used. In the present invention, the components that can be used include, but are not limited to any of desert soil, especially Saharan soil, crustacean shells, insect skins and/or shells, pupal exuviae, any exuviae, marl, shale and combination thereof. The provided components are then milled in order to obtain milled components. The milled components are then solubilized preferably in water. When the milled components are solubilized, the sand, silt and clay fractions form a mixture with the liquid. As the supernatant i.e the liquid part, is separated, the precipitated heavier fraction mainly composed of sand, silt and clay particles also get separated. The liquid part, i.e. the liquefied components are then acidified and reacted with an oxalic acid solution. The reaction yields gaseous hydrocarbons such as methane and ethane. These by-products are preferably removed. The liquid remaining after the reaction with the oxalic acid solution contains dissolved chitosan. The liquid phase is then separated. The chitosan dissolved in the separated liquid phase is precipitated by introducing a base to the said liquid phase. Afterwards, the precipitated chitosan is separated from the rest of the solution.

In an embodiment of the invention, when reacting the components with oxalic acid, vacuum and/or heat might be applied in order to increase the speed of the reaction. Vacuum and heat act as catalysts. The preferred temperature of reaction is 50-70 °C. However, any temperature allowing the reaction to continue may be utili ed. Additionally, the reactants might be stirred. This also increases the speed of the reaction.

After reacting the components with oxalic acid, the solution is allowed to settle. The solution settles under gravity and hence the liquid part containing chitosan gets separated from the precipitates.

After the reaction with oxalic acid, the liquid part containing chitosan is separated from the precipitates by syphoning, or any physical separation model. The pH of the liquid part containing chitosan is preferably adjusted by a base such as NaOH or KOH. The precipitation of chitosan starts as soon as a base is introduced to the said liquid part. At the time of the introduction, the pH of the liquid part is on the acidic side of the pH scale, thus, the precipitation does not require the pH of the solution to be on the basic scale. Nevertheless, a pH level of 7-8 is observed to be the most suitable level for the precipitation. The said pH levels yield the most product, and thus they are preferred.

The precipitated chitosan might be separated by syphoning the supernatant, or by any physical separation technique.

In an embodiment of the invention, after the separation of the liquid phase, the separated liquid phase is filtered. This helps further removing impurities.

Especially for obtaining medical-grade chitosan, it is better for the deacetylation process to be repeated multiple times. In order to achieve this, the resultant chitosan is processed again, according to the inventive process, starting from the step of reacting the components with an oxalic acid solution. The more times the deacetylation is repeated, the purer the resultant chitosan is.

As can be seen on Figure 4, the chitosan obtained by the inventive method has a porous structure. The porous structure renders the chitosan obtained by the inventive method a suitable and effective carrier for drugs.

Claims

1. A method of producing chitosan comprising the steps of;

- providing at least one component comprising chitin,

- milling a component to obtain a milled component, characterized by the steps of

- solubilizing the milled component,

- separating the supernatant,

- reacting the supernatant with an oxalic acid solution,

- separating the liquid phase

- introducing a base for precipitating chitosan

- separating the precipitated chitosan thereby obtaining chitosan.

2. A method of producing chitosan as in Claim 1 , further comprising the step of applying vacuum for increasing the reaction speed.

3. A method of producing chitosan as in Claim 1 , further comprising the step of applying heat for increasing the reaction speed.

4. A method of producing chitosan as in Claim 1 , further comprising the step of filtering the separated liquid phase, after separating the liquid phase.

5. A method of producing chitosan as in Claim 1, wherein the resultant chitosan is reprocessed according to the inventive process, starting from the step of reacting the components with an oxalic acid solution.

6. A chitosan obtained by the method of producing chitosan according to any one of the preceding claims.