Valorization of the Exoskeletons of Crustaceans in Seafood Wastes to Chemicals in Renewable Solvents: A Catalytic and Mechanistic Study

Abstract

Levulinic acid (LA) and γ-valerolactone (GVL) are considered valuable platform chemicals that can be derived from various types of biomass ranging from food wastes to agricultural residues. Herein, the valorization of the exoskeletons of crustaceans in seafood wastes into LA, GVL, acetic acid (AA), and ammonium (NH 4 ) + was studied including the catalytic and mechanistic aspects. Chitin was used as a model compound to optimize the conditions for converting the exoskeletons of crustaceans in seafood wastes using acetic acid (AA) and GVL as bio-originated renewable solvents. The same conditions were applied to convert various pretreated seafood wastes, such as the exoskeletons of crabs and lobsters. The decalcification of the crustacean samples using phosphoric acid was also studied. GVL was also used as a solvent to produce formic acid (FA), LA, NH 4 + , and GVL to simplify the product purification process. The reaction mixture of chitin (0.41 g, equivalent to 2 mmol of N-acetyl-glucosamine) in a mixture of 10 mL of GVL and 1.5 mL of 5 M H 2 SO 4 was heated at 150 °C for 4 h followed by neutralization with additional NH 4 + (NH 4 OH) to result in two phases due to the salting out effect of (NH 4 ) 2 SO 4 . Ru-based Shvo's catalyst was then added to the organic phase for transfer hydrogenation of LA with FA as the hydrogen donor to yield GVL. Uniformly labeled N-acetyl-[ 13 C 6 ]glucosamine (UL-13 C 6 -NAG) was used to confirm the formation of 13 C 5 -GVL in 12 C 5 -GVL via 13 C 5 -LA and 13 C-FA. Detailed in situ NMR studies revealed the presence of two bicyclic compounds, protonated salt of 1,6anhydro-2-deoxy-2-ammonio-glucopyranose (AGluNPH + ) and 1,6-anhydro-2-deoxy-2-ammonio-glucofuranose (AGluNFH + ), as proposed key intermediates of the of UL-13 C 6 -NAG conversion.

Catalytic conversion of chitin-based biomass to nitrogen-containing chemicals

“…successfully detected and quantified ammonium ions using the 1 H NMR technique in the acidolysis of crustacean shells and chitin to 5-HMF, LA, and GVL at 130°C to 150°C. 132 A highly favorable maximum yield of 83% ammonium from chitin was achieved in their reaction system, with the remaining nitrogen contents being incorporated into humins. The acid-catalyzed deamination step could be attained following cleavage of the amide bond through hydrolysis.…”

Strategies to Prepare Chitin and Chitosan-Based Bioactive Structures Aided by Deep Eutectic Solvents: A Review

“…Among natural biopolymers, chitin stands out as the second most abundant natural polymer on Earth (only after cellulose, the principal component of plant cell walls and the most abundant source of renewable polysaccharides on Earth [26]). It can be found in a plethora of living beings [27], with some notable sources being crustacean shells [28][29][30][31][32], arthropods [33], mollusks [34], insects [35][36][37], and fungi [38]. Chemically, chitin is a linear polysaccharide composed by a repetition of subunits of 2-amino-2-deoxy-D-glucose (N-acetyl-glucosamine, GlcNAc, Figure 1a) connected by (β1→4) glycosidic bonds (Figure 1b,c).…”

“…The resultant rigidity bolstered by these hydrogen bonds, along with the substantial bulk of the acetamide substituent, not only imparts inflexibility to the chains but also restricts rotation along the glycosidic bonds linking the monosaccharides, leading to highly stable chain conformations (Khoushab and Yamabhai, 2010). Chitin present in its primary natural reservoir, namely crustacean shells [28][29][30][31][32], adopts an antiparallel orientation (α- The resultant rigidity bolstered by these hydrogen bonds, along with the substantial bulk of the acetamide substituent, not only imparts inflexibility to the chains but also restricts rotation along the glycosidic bonds linking the monosaccharides, leading to highly stable chain conformations (Khoushab and Yamabhai, 2010). Chitin present in its primary natural reservoir, namely crustacean shells [28][29][30][31][32], adopts an antiparallel orientation (α-chitin), in which not only intramolecular but also intermolecular hydrogen bonding is present (Figure 1d, red color), resulting in an orthorhombic crystal structure [27,43].…”

“…Chitin present in its primary natural reservoir, namely crustacean shells [28][29][30][31][32], adopts an antiparallel orientation (α- The resultant rigidity bolstered by these hydrogen bonds, along with the substantial bulk of the acetamide substituent, not only imparts inflexibility to the chains but also restricts rotation along the glycosidic bonds linking the monosaccharides, leading to highly stable chain conformations (Khoushab and Yamabhai, 2010). Chitin present in its primary natural reservoir, namely crustacean shells [28][29][30][31][32], adopts an antiparallel orientation (α-chitin), in which not only intramolecular but also intermolecular hydrogen bonding is present (Figure 1d, red color), resulting in an orthorhombic crystal structure [27,43]. Conversely, β-chitin (present in squid pens, clams, oyster shells, and bones of cuttlefish, [34]) features a parallel chain alignment, with no interchain bonding, giving rise to a monoclinic crystal symmetry [43] with higher solubilizing properties.…”