Hello everyone, my name is Melody Kimi from University Malaysia Sarawak. I'm going to present a method to obtain the valuable chitosan from marine shell waste in just one step using a new extraction solution. This is the main idea of this project entitled Direct Extraction of Chitosan from Marine Shell Waste by Natural Deep Eutectic Solvent.
According to National Solid Waste Management Department, approximately 45% of waste generated every day in Malaysia is food waste. In line with sustainable consumption and production, in Sustainable Development Goals 12, the valuable compounds from food waste can be extracted to form useful products while also reducing pollution. Marine shells are usually discarded as food waste in seafood industries. Marine shells waste contain a useful compound which is known as chitin.
Chitin is made up of amino polysaccharide polymer which can be used to replace synthetic polymer. Approximately 25% dry weight of marine shells consisted of chitin. However, chitin has limited uses due to its poor reactivity.
This can be overcome by a chemical process known as deacetylation of chitin to convert chitin to chitosan. Chitosan is a biodegradable biopolymer containing active functional groups which can be processed into various structures to suit its application such as encapsulation of substrate as biofilm or as binder or delivery of substrate. However, commercial kaitosan must be extracted from marine shell waste using three main steps which includes demineralization, deproteinization and deacetylation.
These steps often employ harsh chemicals under high temperature to remove the resistant calcium carbonate and protein found in marine shells. To overcome this, there is an alternative method to this conventional method. This alternative method uses a solution known as natural deep eutectic solvent, also known as NADES.
NADES is made up of at least two natural metabolite components. The natural metabolite components must behave as hydrogen bond acceptor and hydrogen bond donor. However, current NADES synthesized so far only managed to extract chitin from marine shell waste. There is still a need to use strong base for deacetylation of chitin to chitosan. The importance of deacetylation process is to produce the amino group of chitosan which contributes to its reactivity.
Current NADES only reduces the steps to obtain chitosan. It does not eliminate the usage of harsh chemicals. In order to solve this shortcoming of the current NADES, a new NADES solution which can obtain chitosan directly from marine shells is needed. Recently, in 2019, there have been a report published in Nature which states that acetogenin solution is capable of extracting chitosan from marine shells. Acetogenin is a main component in Graviola leaves.
Graviola is commonly known as soursop. A recent study has found that deacetylation reaction of chitin to chitosan is facilitated by the nucleophilic attack of hydroxyl groups from acetogenin on the carbonyl group of chitin. This process, however, is time-consuming. To enhance the rate of reaction of chitosan extraction using acetone, Acetogenin as hydrogen bond donor is mixed with another component as hydrogen bond acceptor. We found that choline chloride can act as hydrogen bond acceptor which can be paired with acetogenin.
Choline chloride, a biodegradable, affordable, non-toxic quaternary ammonium chloride salt, can be extracted from biomass. as the hydrogen bond acceptor. These two components form a new NADES solution. With this NADES solution, pure chitosan can be extracted in just 2 hours.
It eliminates the use of harsh chemicals and the extraction can proceed in room temperature, without any heating. The Kaitosan obtained by this method has lower moisture content, higher degree of deacetylation, higher molecular weight compared to the commercial Kaitosan. These features enhance the reactivity and strength of the polymer Kaitosan. The current approach using newly synthesized NADES is a sustainable single-step process with enhanced properties compared to the conventional way of extraction using strong acid and base under high temperature. The extracted chitosan will be safe to be used in food industries, medical field and agricultural industries as zero harmful reagent is applied during the extraction process.
Nades Extraction Solution enables a sustainable approach in valorization of marine shell waste to biopolymer chitosan. Natural solution for natural chitosan. Thank you for listening.