Extraction of Chitin from Green Crab Shells by Mechanochemistry and Aging

Abstract

Crustacean shell waste is one of the most important chitin sources for commercial use due to its low price and high availability. The extraction of chitin from this residue relies on two removal steps: one for proteins and another one for minerals. Herein, we report a "solvent-free", one-pot process relying on mechanochemistry and aging to convert crustacean shells into chitin with high yields and low ash content. The extraction was performed on European Green Crabs, one of the world's most damaging invasive species, thus converting a serious environmental threat into a biomaterial opportunity. Successful chitin isolation of Green Crabs was achieved by milling of solid acids (i.e., citric, ascorbic, malic, succinic, and salicylic acid) for 10 to 30 min, while a combination of milling and aging was necessary for aqueous acids (i.e., hydrochloric and acetic acid). Milling, aging times, and shell to acid ratios were optimized, while the process could be scaled to 200 g of shell starting materials. This method required limited chemical and energy inputs, which were quantified by sustainability metrics. The process reported is a more sustainable approach for chitin production over the current industrial methods and has the potential to be extended to other chitin sources (e.g., lobster, shrimp, and insects).

Environmental Impact Assessment of Chitin Nanofibril and Nanocrystal Isolation from Fungi, Shrimp Shells, and Crab Shells

“…Accordingly, future works should implement greener approaches to raw chitin isolation before nanochitin synthesis. Recent advances in the field include the use of solvent-free mechanochemistry to extract chitin from crab shells, or transition-metal salt aqueous solutions with ionic liquids to extract α-chitin from shrimp shells (purities reaching 96.5 wt %) . Overall, these processes circumvent the need of NaOH or HCl, lowering waste volumes and associated environmental impacts.…”

“…Weak organic acids such as oxalic, lactic, or citric acid can replace inorganic acids such as HCl or H 2 SO 4 during biobased colloid isolation, so their use can be a priori considered to lower the total environmental impacts of chitin nanoparticle isolation. Accordingly, recent investigations have tapped onto the replacement of HCl or H 2 SO 4 by weak organic acids such as citric acid, malic acid, or ascorbic acid, or novel extraction approaches involving biobased natural deep eutectic solvents (NADES) composed of hydrogen bond donors and acceptors that adhere to the Green Chemistry principles . As weak organic acids and NADES (generally) feature lower toxicities, better biocompatibilities, and enhanced environmental sustainability over inorganic acids, their use should be translated into a more sustainable process to extract biomass nanoparticles.…”

A bio-based click reaction leading to the dihydropyridazinone platform for nitrogen-containing scaffolds

“…Recent investigations toward this end have revealed a great potential of chitin as a source compound for N-containing chemicals synthesis, due to its shear abundance and high N content (∼7 wt%). 25 Several appealing products, such as N -acetylglucosamine, 26 and 3-acetamido-5-acetylfuran 27 and its derivatives, 28 could be selectively prepared. Unfortunately, the molecular structure types of the resulting products are still rare.…”

Controlled Chitosan Molecular Weight Reduction by Mechanochemical and Aging-based Phosphoric Acid Hydrolysis

“…35 Besides reactions happening during mechanical treatment, the concept of aging has been introduced, in which reactions take place in the solid phase, after an initial mixing phase. 36 These solid-state methodologies are well suited in the context of biomass conversion, especially because such starting materials tend to be insoluble, 37 and have shown great promise in the context of chitin extraction, 38,39 and conversion. 39,40 Mechanochemistry has been used for the deacetylation of chitin into chitosan in a process pioneered by Yan and co-workers.…”