It was not long ago that pictures and videos of huge quantities of dead shrimp spread on Mirbat Beach in the Dhofar Governorate, south of the Sultanate of Oman, until the official directives that preceded the announcement of the causes of the deaths were to warn against using them as food.
The authorities announced that the causes of death were due to climatic factors, namely the sudden change in sea water temperatures and the lack of dissolved oxygen. However, whatever the reasons, shrimp are very sensitive creatures, and as soon as they leave their aquatic environment and die, a rapid decomposition process occurs to them, especially in open air, which leads to the accumulation of harmful bacteria within a few hours and becomes a fertile environment for intestinal toxins.
However, these reasons that prevent it from being eaten as food do not hinder its use in the production of “chitosan”, which is the second largest biopolymer in the world after cellulose, and the raw material used in the manufacture of the most expensive medicines. It is also used in many industrial and environmental applications, which is what earned it the status of “sea gold.”
Steps to manufacture chitosan
Chitosan is mainly made from shrimp shells, so the dead shrimp in the Omani case remains a mine that can be exploited, even if the meat is spoiled or poisoned by bacteria that prevent it from being eaten.
Dr. Alaa Al-Muhtasib, associate professor at the Department of Chemical Engineering at Sultan Qaboos University, told Al Jazeera Net, “The carbon structure of the shell is not affected, and the harsh chemical processes by which chitosan is made will act as superior sterilization, making the final product safe for water treatment and medical and pharmaceutical uses.”
The process of manufacturing chitosan, as Alaa explains, begins with removing the peels from the meat, starting a series of chemical processes that begin with getting rid of the calcium carbonate and minerals that give the peel its hardness, by soaking it in hydrochloric acid, then preparing it for a second stage that aims to get rid of the organic tissues and proteins attached to the peels to obtain the pure “chitin” substance, which is done using sodium hydroxide.
To obtain a pure, transparent or white product far from natural shrimp pigments, the isolated chitin is treated with hydrogen peroxide, and to convert the chitin into the required chitosan, it is treated again with sodium hydroxide.
The specifications of Omani shrimp differ from others, as their shells are often thicker and denser, which means a higher concentration of the raw material, according to a study by researchers from the University of Nizwa in Oman that documented this feature.
According to this study published in the journal Carbohydrate Research, the researchers were able to extract more than 530 grams of pure chitosan from every kilogram of peels, a production efficiency that places the Sultanate of Oman at the forefront of countries capable of investing in its marine waste.
Encouraging prices.. pure extraction protocol
In addition to the efficiency of chitosan production provided by the specifications of Omani shrimp shells, the chitosan produced from them can reach high levels of purity, qualifying it to be sold at very high prices.
Like gold ore, the price of chitosan varies based on the “degree of purity.” While the raw material with the lowest degree of purity is sold by the kilogram, and ranges between 20 and 150 dollars per kilogram, the higher purity types used in surgery, bandages, and the manufacture of medicines are sold by the gram, and according to the prices recorded on the “nanochemazone” website, which specializes in selling chemical materials, the price of a gram of this high-purity raw material has reached $274 per gram.
An Omani study published in the journal Water-Energy Nexus established a protocol for reaching a purity that qualifies chitosan for medical uses.
This protocol, which was reached after implementing 27 repeated laboratory experiments, envisions the optimal conditions for production, starting with the second step in the chitosan production process, which is chitin extraction. The study found that the best concentration of materials used in extraction is 3% hydrochloric acid at a temperature of 25 degrees Celsius for one hour, followed by the use of 50% sodium hydroxide at 110 degrees Celsius for 3 hours to remove proteins in the next stage, which achieves an extraction efficiency of about 53.31%.
In the final stage, the chitin is bleached using hydrogen peroxide at a concentration of 30% for 3 hours, then converted into chitosan through alkaline treatment using sodium hydroxide at a concentration of 50% for 15 minutes.
Various medical applications
This pure chitosan is used as a smart carrier for therapeutic materials, and as a study published in the Journal of Drug Targeting indicates, this contributes to improving the absorption of the drug within the body and controlling the speed of its release, which allows reducing doses and improving therapeutic effectiveness.
As for tissue engineering, a study published in the Journal of Materials Chemistry B indicated its effectiveness as a material that supports cell growth, as it is used in developing biological structures that help restore bones, cartilage, and skin tissue. It is seen as a promising element in regenerative medicine due to its ability to support the rebuilding of damaged tissues.
In the context of surgical care, a third study published in the journal Novel Biomaterials for Regenerative Medicine indicates the use of chitosan in the manufacture of advanced medical dressings that help accelerate wound healing and reduce inflammation, in addition to its antimicrobial properties that contribute to reducing the risk of infection. It is also used in the manufacture of bleeding-stopping materials and absorbable surgical sutures.
Its applications are also expanding in the fields of oncology and diabetes, where it is used as an intermediary in the delivery of cancer drugs with the aim of reducing their side effects, according to a study published in the journal Biotechnology Advances, in addition to its potential role in improving the body’s response to metabolic treatments and regulating glucose levels, according to a study published in the Journal of Drug Delivery Science and Technology.
Water treatment and other applications
In addition to these medical applications for high-purity species, Dr. says: Alaa Al-Muhtasib said that less pure types of chitosan can be used in wastewater treatment, as it has distinct absorption properties that enable it to remove suspended materials in wastewater, in addition to its ability to bind to toxic heavy metal ions such as lead, cadmium, and nickel, which makes it an effective material in modern biotreatment techniques.
Studies also indicate that the use of chitosan leads to a reduction in indicators of organic pollution in water, such as biological oxygen demand (BOD) and chemical oxygen demand (COD), which are two basic standards for measuring the degree of wastewater pollution, and this reduction reflects a clear improvement in water quality after treatment.
In addition to these applications, chitosan is used as a plant growth stimulant and plant immunity enhancer, as it helps enhance crop resistance to fungal and bacterial diseases, according to a study published in the journal Agriculture.
It is also used in seed coatings and improving the efficiency of fertilizers thanks to its ability to gradually release nutrients, according to a study published by the International Journal of Biological Macromolecules.
In the food industry, a study published by the journal Food Chemistry indicates its use in food preservation by forming thin biofilms on the surface of fresh products, which extends their shelf life and limits the growth of microbes. It is also used in the biopackaging industry as an environmentally friendly alternative to traditional plastic materials, according to a study published by the Journal of Agriculture and Food Research.
In the industrial field, it is used in the paper and textile industry to improve the properties of strength, luster and durability.
Alaa says, “This diversity of uses reflects the flexibility of the chemical composition of chitosan and the possibility of modifying it to serve multiple applications, which means that dead shrimp, if their shells are exploited, can be transformed from an environmental burden into a gold mine.”
