A method for extracting chitosan using black soldier flies

Abstract

The present invention belongs to the field of natural product extraction, and specifically relates to a method for extracting chitosan using black soldier flies in a high-value manner. The present invention uses an ionic liquid while extracting chitosan using a low eutectic solvent method. The low eutectic solvent can form a strong interaction with the chitin molecules, and the ionic liquid can further enhance the specific recognition of the chitin molecules. The two act synergistically, thereby improving the solubility and recognition of chitosan, efficiently removing proteins and salts, and avoiding the hydrolysis and cleavage of the glycosidic bonds of the chitin macromolecular main chain, thereby significantly improving the extraction rate and purity of chitosan. The extraction conditions of the present invention are mild, and the low eutectic solvent can be recycled and reused, which simplifies the chitosan extraction process and is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the field of natural product extraction, and particularly relates to a method for extracting chitosan by utilizing black soldier flies. Background Art

[0002] Chitosan, also known as chitosan, polyglucosamine, and soluble chitin, is the only alkaline polysaccharide among natural polysaccharides and the only cationic alkaline polysaccharide. As a natural polymer, chitosan possesses inherent advantages in being edible, biodegradable, biocompatible, safe, and non-toxic, making it widely used in industries such as food, healthcare, and agriculture.

[0003] Chitosan is typically extracted from the shells of marine organisms such as shrimp, crab, and shellfish. However, shrimp and crab shells contain low levels of chitin and high levels of inorganic salts (over 30%). This leads to inconsistent chitosan yield and quality, and high extraction costs, hindering widespread application. The black soldier fly (Hermetia illucens) is a unique insect capable of producing fertilizer, protein, and fat, and also serving as a source of other important bioactive substances such as chitin, chitosan, and melanin. The chitosan content in black soldier flies varies at different stages (larval, prepupal, pupal, and mature). According to literature (CN115260339A), the chitosan content in the shells of prepupal flies is the highest, and the extraction rate is also the highest at this time, which can be maximized. Secondly, in the prepupal stage, chitosan is mainly enriched in the shells, while the visceral fat is mainly protein, which can be made into feed for pets, poultry, etc. The shells and viscera can be separated, and the former can be used to extract chitosan and the latter can be used as feed to maximize economic benefits.

[0004] Currently, the main processes for extracting chitosan from black soldier flies include acid-base extraction, microwave-assisted extraction, and enzymatic hydrolysis.

[0005] CN102585035A discloses a method for extracting chitosan from black soldier flies, which involves demineralization with dilute acid, deproteinization with dilute alkali, depigmentation with sodium hypochlorite, and deacetylation with concentrated alkali. However, due to the need for concentrated alkali and high temperatures, under these conditions, the concentrated alkali solution not only promotes the hydrolysis of acetyl groups but also hydrolyzes and cleaves the glycosidic bonds of the macromolecular backbone, reducing the relative molecular weight and the extraction yield.

[0006] CN106832054A uses black soldier fly adults as raw materials to extract chitosan. The deacetylation process adopts a microwave-assisted method combined with an enzymatic method. The microwave-assisted method first removes some acetyl groups, while activating chemical bonds and substitution sites. Subsequently, chitosan deacetylase reacts, greatly improving the degree of deacetylation. The degree of deacetylation is as high as 95.6-97.3%, obtaining good-quality chitosan, avoiding the hydrolysis and cleavage of the glycosidic bonds of the chitosan macromolecular backbone, and avoiding the pollution and waste caused by the use of high-concentration alkali solution. However, the microwave-assisted method has the disadvantages of using too high a sodium hydroxide concentration and too long a microwave heating time. The source of deacetylase is not easy, and the enzyme amount required to achieve a higher degree of deacetylation is large. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a method for extracting chitosan using black soldier flies, which has mild extraction conditions for chitosan, high extraction rate and high chitosan purity. In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for extracting chitosan using black soldier flies comprises the following steps:

[0009] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and sieving to obtain black soldier fly pupa shell powder;

[0010] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) is mixed with a solvent and subjected to Soxhlet extraction at 35-65°C for 8-15 hours. The mixture is filtered and the liquid component is desolvated at 35-65°C to obtain oil and recovered solvent, respectively. The oil is repeatedly washed with the recovered solvent, and the resulting solid component is dried to obtain defatted black soldier fly pupa shell powder. The solvent is one or more of petroleum ether, acetone, and toluene; the mass-to-volume ratio of black soldier fly pupa shell powder to solvent is 1 g: 20-40 mL.

[0011] Step 3) preparing a deep eutectic solvent: mixing a hydrogen bond acceptor and a hydrogen bond donor, stirring them uniformly, and heating them to obtain a deep eutectic solvent; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2-4;

[0012] Step 4) preparing an ionic liquid solution: dissolving an ionic liquid in ethanol, stirring uniformly and heating to obtain an ionic liquid solution; the ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium sulfonate, and 1-ethyl-3-methylimidazolium tetrafluoroborate;

[0013] Step 5) preparing chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), reacting in a water bath at 65-85°C for 3-5 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding an aqueous solution of H2O2 at a ratio of 1 g: 20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, allowing to stand, centrifuging, washing, and drying to obtain chitosan;

[0014] Step 6) Preparation of chitosan: The chitin prepared in step 5) is mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80-120° C. for 3-5 h, filtered, washed, and dried to obtain chitosan.

[0015] In some embodiments, the hydrogen bond donor in step 3) is one or more of lactic acid, urea, acetamide, methylurea, imidazole, pyridine, glycerol, butanediol, amino acid and glucose, and the hydrogen bond acceptor is one or more of choline chloride and betaine.

[0016] In some embodiments, in step 3), the hydrogen bond donor is lactic acid and imidazole, and the hydrogen bond acceptor is choline chloride; the molar ratio of choline chloride to lactic acid and imidazole is 1:1:1-3.

[0017] In some embodiments, in step 3), the hydrogen bond donor is lactic acid and imidazole, and the hydrogen bond acceptor is betaine; the molar ratio of betaine to lactic acid and imidazole is 1:1:1-3.

[0018] In some embodiments, in step 4), the solid-to-liquid ratio of the ionic liquid to ethanol is 1 g: 100-200 mL.

[0019] In some embodiments, in step 5), the solid-to-liquid ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and ionic liquid solution is 1 g: 10-30 mL: 5-15 mL.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) While extracting chitosan using a deep eutectic solvent method, the present invention also introduces an ionic liquid. The deep eutectic solvent can form a strong interaction with the chitin molecules, and the ionic liquid can further enhance the specific recognition of the chitin molecules, thereby improving the solubility and recognition of chitosan. The synergistic effect of the two makes the chitosan in black soldier flies highly soluble and selective, effectively removes protein and salt, and significantly improves the extraction rate and purity of chitosan.

[0022] 2) The present invention uses two specific hydrogen bond donors, lactic acid and imidazole, and a hydrogen bond acceptor to form a deep eutectic solvent, which interacts with the ionic liquid. The deep eutectic solvent and the ionic liquid have the same imidazole, carboxyl and other groups, and can form a stable eutectic solution, exerting a synergistic effect. Through intermolecular forces such as hydrogen bonds, they form a strong interaction with the chitin molecules, which can not only efficiently remove protein and salt, but also avoid the hydrolysis and cleavage of the glycosidic bonds in the main chain of the chitin macromolecule, thereby significantly improving the extraction rate and purity of chitosan.

[0023] 3) The extraction conditions of the present invention are mild, and the deep eutectic solvent can be recycled and reused, which simplifies the extraction process of chitosan, is environmentally friendly, and is suitable for industrial production. DETAILED DESCRIPTION

[0024] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. The following contents are merely illustrative of the scope of the present invention. Those skilled in the art may make various changes and modifications to the present invention based on the disclosed contents, and such changes and modifications should also fall within the scope of the present invention. The present invention will be further described below by way of specific examples.

[0025] Chitosan extraction rate = extracted chitosan mass / chitosan mass in black soldier fly shell x 100%;

[0026] Chitosan purity = mass of chitosan in extract / mass of extract x 100%.

[0027] The content of chitosan was determined by ninhydrin colorimetry.

[0028] Example 1

[0029] A method for extracting chitosan using black soldier flies comprises the following steps:

[0030] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0031] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0032] Step 3) preparing a deep eutectic solvent: mixing hydrogen bond donor lactic acid and imidazole with hydrogen bond acceptor choline chloride, and stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to lactic acid and imidazole is 1:1:1.5;

[0033] Step 4) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0034] Step 5) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), wherein the solid-liquid ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and the ionic liquid solution is 1 g:25 mL:5 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding a 20 wt% H2O2 aqueous solution at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, standing, centrifuging, washing, and drying to obtain chitin;

[0035] Step 6) Preparation of chitosan: The chitin prepared in step 5) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0036] Example 2

[0037] A method for extracting chitosan using black soldier flies comprises the following steps:

[0038] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0039] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0040] Step 3) preparing a deep eutectic solvent: mixing lactic acid (a hydrogen bond donor) and choline chloride (a hydrogen bond acceptor), stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to lactic acid is 1:2.5;

[0041] Step 4) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0042] Step 5) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), wherein the solid-liquid ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and the ionic liquid solution is 1 g:25 mL:5 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding a 20 wt% H2O2 aqueous solution at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, standing, centrifuging, washing, and drying to obtain chitin;

[0043] Step 6) Preparation of chitosan: The chitin prepared in step 5) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0044] Example 3

[0045] A method for extracting chitosan using black soldier flies comprises the following steps:

[0046] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0047] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0048] Step 3) preparing a deep eutectic solvent: mixing a hydrogen bond donor, imidazole, and a hydrogen bond acceptor, choline chloride, and stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to imidazole is 1:2.5;

[0049] Step 4) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0050] Step 5) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), wherein the solid-liquid ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and the ionic liquid solution is 1 g:25 mL:5 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding a 20 wt% H2O2 aqueous solution at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, standing, centrifuging, washing, and drying to obtain chitin;

[0051] Step 6) Preparation of chitosan: The chitin prepared in step 5) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0052] Example 4

[0053] A method for extracting chitosan using black soldier flies comprises the following steps:

[0054] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0055] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0056] Step 3) preparing a deep eutectic solvent: mixing lactic acid and methylurea as hydrogen bond donors and choline chloride as hydrogen bond acceptor, and stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to lactic acid and methylurea is 1:1:1.5;

[0057] Step 4) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0058] Step 5) Extracting chitosan: Mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4) at a solid-liquid ratio of 1 g: 25 mL: 5 mL, reacting in a 75°C water bath for 4 hours, filtering, and centrifuging the filtrate to obtain a precipitate, washing, and drying. A 20 wt% H2O2 aqueous solution is added at a ratio of 1 g: 20-40 mL, and the mixture is uniformly mixed. The pH value is adjusted to 7.5, decolorized, allowed to stand, centrifuged, washed, and dried to obtain chitosan;

[0059] Step 6) Preparation of chitosan: The chitin prepared in step 5) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0060] Example 5

[0061] A method for extracting chitosan using black soldier flies comprises the following steps:

[0062] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0063] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0064] Step 3) preparing a deep eutectic solvent: mixing hydrogen bond donors lactic acid and pyridine with a hydrogen bond acceptor choline chloride, and stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to lactic acid and pyridine is 1:1:1.5;

[0065] Step 4) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-to-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0066] Step 5) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), wherein the solid-liquid ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and the ionic liquid solution is 1 g:25 mL:5 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding a 20 wt% H2O2 aqueous solution at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, standing, centrifuging, washing, and drying to obtain chitin;

[0067] Step 6) Preparation of chitosan: The chitin prepared in step 5) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0068] Comparative Example 1

[0069] A method for extracting chitosan using black soldier flies comprises the following steps:

[0070] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0071] Step 2) Preparing defatted black soldier fly pupa shell powder: mixing the black soldier fly pupa shell powder prepared in step 1) with petroleum ether at a solid-liquid ratio of 1 g:40 mL, performing Soxhlet extraction at 50° C. for 12 hours, filtering, and desolvating the liquid component at 50° C. to obtain oil and recovered solvent, respectively. The oil is repeatedly washed with the recovered solvent, and the resulting solid component is dried to obtain defatted black soldier fly pupa shell powder;

[0072] Step 3) preparing a deep eutectic solvent: mixing hydrogen bond donor lactic acid and imidazole with hydrogen bond acceptor choline chloride, and stirring at 75° C. to obtain a transparent liquid; wherein the molar ratio of choline chloride to lactic acid and imidazole is 1:1:1.5;

[0073] Step 4) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) at a solid-liquid ratio of 1 g:30 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying. A 20 wt% H2O2 aqueous solution is added at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, allowing to stand, centrifuging, washing, and drying to obtain chitin;

[0074] Step 5) Preparation of chitosan: The chitin prepared in step 4) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0075] Comparative Example 2

[0076] A method for extracting chitosan using black soldier flies comprises the following steps:

[0077] Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and passing through a 60-mesh sieve to obtain black soldier fly pupa shell powder;

[0078] Step 2) Preparing defatted black soldier fly pupa shell powder: The black soldier fly pupa shell powder prepared in step 1) was mixed with petroleum ether at a solid-liquid ratio of 1 g:40 mL, subjected to Soxhlet extraction at 50° C. for 12 hours, filtered, and the liquid component was desolvated at 50° C. to obtain oil and recovered solvent, respectively. The oil was repeatedly washed with the recovered solvent, and the resulting solid component was dried to obtain defatted black soldier fly pupa shell powder;

[0079] Step 3) preparing an ionic liquid solution: dissolving 1-ethyl-3-methylimidazolium acetate in ethanol and stirring at 50° C. to obtain an ionic liquid solution; the solid-liquid ratio of the 1-ethyl-3-methylimidazolium acetate to ethanol is 1 g:100 mL;

[0080] Step 4) Extracting chitosan: mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the ionic liquid solution prepared in step 3) at a solid-liquid ratio of 1 g:30 mL, reacting in a 75°C water bath for 4 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding a 20 wt% H2O2 aqueous solution at a ratio of 1 g:20-40 mL, mixing evenly, adjusting the pH to 7.5, decolorizing, allowing to stand, centrifuging, washing, and drying to obtain chitosan;

[0081] Step 5) Preparation of chitosan: The chitin prepared in step 4) was mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80° C. for 3 h, filtered, washed, and dried to obtain chitosan.

[0082] Table 1 Extraction results of chitosan using black soldier flies

[0083] Extraction rate / % purity / % Example 1 92.6 98.5 Example 2 84.4 92.8 Example 3 87.1 93.7 Example 4 81.5 90.2 Example 5 82.7 91.6 Comparative Example 1 64.9 89.4 Comparative Example 2 47.6 92.3

[0084] According to the results shown in Table 1, it can be seen from the comparison between Example 1 and Comparative Example 1 and Comparative Example 2 that in Example 1 of the present invention, when extracting chitosan from black soldier flies, a deep eutectic solvent and an ionic liquid are used simultaneously, and a higher extraction rate of chitosan is achieved, and the obtained chitosan has a higher purity. This may be because the deep eutectic solvent can form a strong interaction with the chitin molecules, and the ionic liquid can further enhance the specific recognition of the chitin molecules, change the spatial conformation of the chitin, thereby improving the solubility and recognition of the chitosan, and the deep eutectic solvent and the ionic liquid have the same imidazole, carboxyl and other groups. The two work synergistically, so that the chitosan in the black soldier fly has high solubility and selectivity, efficiently removes protein and salt, and significantly improves the extraction rate and purity of the chitosan.

[0085] From the comparison between Example 1 and Example 2, Example 3, Example 4, and Example 5, it can be seen that Example 1 of the present invention uses two specific hydrogen bond donors, lactic acid and imidazole, and a hydrogen bond acceptor to form a low eutectic solvent, which interacts with the ionic liquid to exert a synergistic effect, and can form a stable eutectic solution. It forms a strong interaction with the chitin molecules through intermolecular forces such as hydrogen bonds, which can not only efficiently remove protein and salt, but also avoid the hydrolysis and cleavage of the glycosidic bonds in the main chain of the chitin macromolecule, thereby significantly improving the extraction rate and purity of chitosan.

[0086] The above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for extracting chitosan using black soldier flies, comprising the following steps: Step 1) preparing black soldier fly pupa shell powder: taking black soldier fly pupa shells, washing with water, washing with alcohol, washing with water again, drying, grinding, and sieving to obtain black soldier fly pupa shell powder; Step 2) Preparing defatted black soldier fly pupa shell powder: mixing the black soldier fly pupa shell powder prepared in step 1) with a solvent, performing Soxhlet extraction at 35-65° C. for 8-15 hours, filtering, and desolvating the liquid component at 35-65° C. to obtain oil and recovered solvent, respectively. The oil is repeatedly washed with the recovered solvent, and the resulting solid component is dried to obtain defatted black soldier fly pupa shell powder; Step 3) preparing a deep eutectic solvent: mixing a hydrogen bond acceptor and a hydrogen bond donor, stirring them uniformly, and heating them to obtain a deep eutectic solvent; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2-4; the hydrogen bond donor is lactic acid and imidazole, and the hydrogen bond acceptor is choline chloride; Step 4) preparing an ionic liquid solution: dissolving an ionic liquid in ethanol, stirring and heating to obtain an ionic liquid solution; the ionic liquid is 1-ethyl-3-methylimidazolium acetate; Step 5) Preparing chitosan: Mixing the defatted black soldier fly pupa shell powder prepared in step 2) with the deep eutectic solvent prepared in step 3) and the ionic liquid solution prepared in step 4), reacting in a water bath at 65-85°C for 3-5 hours, filtering, centrifuging the filtrate to obtain a precipitate, washing, and drying, adding an aqueous H2O2 solution at a ratio of 1 g: 20-40 mL and mixing evenly, adjusting the pH to 7.5, decolorizing, allowing to stand, centrifuging, washing, and drying to obtain chitosan; the feed ratio of the defatted black soldier fly pupa shell powder to the deep eutectic solvent and the ionic liquid solution is 1 g: 10-30 mL: 5-15 mL; Step 6) Preparation of chitosan: The chitin prepared in step 5) is mixed with a 35 wt% NaOH aqueous solution, deacetylated at 80-120° C. for 3-5 h, filtered, washed, and dried to obtain chitosan.

2. The method for extracting chitosan using black soldier flies according to claim 1, wherein: In step 2), the solvent is one or more of petroleum ether, acetone, and toluene; and the mass-to-volume ratio of the black soldier fly pupa shell powder to the solvent is 1 g: 20-40 mL.

3. The method for extracting chitosan using black soldier flies according to claim 1, wherein: The molar ratio of hydrogen bond acceptor to lactic acid and imidazole is 1:1:1-3.

4. The method for extracting chitosan using black soldier flies according to claim 1, wherein: Step 4) The feed ratio of the ionic liquid to ethanol is 1 g: 100-200 mL.