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Blue mussel (Mylitus edulis) shells are composed of an outer prismatic calcite layer and an inner nacreous aragonite layer. They are a by-product of the seafood industry and a potential feedstock in the ocean- or marine-biorefinery. Heat treatment of these shells can yield four CaCO3 materials with differing ratios of aragonite and calcite, and separation of the aragonite and calcite. Infrared spectroscopy (IR) and powder X-ray diffraction (XRD) revealed that when shells are heated (120–220 °C, 48 h), the ratios of aragonite and calcite change. The organic matrix, made up of silk-fibroin like proteins, β-chitin and glycoproteins, was revealed by 1H MAS NMR spectroscopy and shows previously unreported resonances in mollusc shells at chemical shifts typical for amides and aromatic groups. Heat treatment of the shells caused a large decrease in organic matrix levels as shown by 1H MAS NMR spectroscopy and this reduction in matrix content leads to a simple way to separate the prismatic calcite layer from the nacreous layer, allowing easy isolation of natural platelets of nacre. The prismatic calcite layer still contains some organic matrix whereas only about 0.02 wt% matrix remains in the nacreous layer. Using mussel protein hydrolysate (another by-product of the seafood industry) as an additive, artificial nacre was synthesized using a CaCl2 and Na2CO3 mixing method. Good polymorph control was seen, and new platelets of nacre can be seen growing on the surface of a mussel shell that was used for seeding in the presence of mussel protein hydrolysate.

Mussels are a high protein food grown using aquacultural methods around the world. By-product streams from this industry include raw discards (small or damaged product) and cooked shells that retain their posterior adductor muscle. Mollusc shells are primarily calcium carbonate and for blue mussels, Mytilus edulis, the shell accounts for up to 70% of their mass. The shell by-product streams could be used in a range of applications but shell storage without protein removal is problematic. In this study, we studied the potential of two enzymes (Multifect PR 6L and PR 7L) to remove protein from mussel shells using an initial screening and Design of Experiments approach. The enzymatic cleaning experiments were monitored using either thermogravimetric analysis or via manual recovery and weighing of protein residue still on shells. 20 g mussel shells with raw protein attached were efficiently cleaned using 1.0–2.0 μL g−1 Multifect PR 6L in seawater or tap water for 4 h at 55.0 °C. 20 g mussel shells with cooked protein attached were efficiently cleaned using 6.0 μL g−1 Multifect PR 7L in seawater or synthetic seawater for 10 h at 25.0 °C. As the developed methods do not require any additives (i.e. no need for pH adjustment), scale up to integrate into existing seafood processing facilities will be relatively straightforward and would provide two product streams: a biorenewable calcium carbonate and protein hydrolysate. Initial trials using freeze-dried mussel protein hydrolysate from this work to feed zebrafish (Danio rerio) over the course of 18 months have shown success.

Research into renewable chemicals, fuels and materials sourced from the oceans at Memorial University and elsewhere is employing green chemical technologies for the transformation of algae and food industry waste streams into useful products. A very small proportion of biomass utilization research is currently focused on these feedstocks and efforts focused in this area could reduce land space competition between food and chemical/fuel production. This perspective highlights some of the achievements and potential opportunities surrounding the use of algae and waste from shellfish and finfish processing. In particular, investigations in this field have used alternative solvents (water, supercritical carbon dioxide and methanol or ionic liquids) extensively. Supercritical Fluid Extraction (SFE) has been used to extract lipids and pigments from algae, and oils from fish-processing plant waste streams. Water can be used to isolate potentially high value biologically-active oligosaccharides from some seaweeds. Biotechnological approaches are showing promise in the separation of biopolymers from shellfish waste streams. Production of new nitrogen-containing bioplatform chemicals (e.g. 3-acetamido-5-acetylfuran) from aminocarbohydrates (chitin, chitosan and N-acetylglucosamine) is being pursued.

A novel route has been developed that yields levulinic acid (4-oxopentanoic acid, LA) and 5-hydroxymethylfurfural (5-HMF) from chitosan. Hydrolysis of chitosan was performed in the presence of a range of Lewis acids with SnCl4·5H2O providing the best results. All reactions were performed in sealed vessels under microwave irradiation at 200 °C for 30 min. Typical pressures achieved were 17 to 19 bar. 23.9 wt% LA was produced from 100 mg chitosan using 0.24 mmol SnCl4·5H2O and 4 mL water. Under more dilute conditions, 10.0 wt% 5-HMF was obtained using 0.12 mmol SnCl4·5H2O and 15 mL water. We propose that under more concentrated reaction conditions the 5-HMF formed reacts further to produce LA. When chitin is treated similarly, no 5-HMF is produced but up to 12.7 wt% LA can be obtained. For comparison, 32.0 wt% LA was produced from 100 mg glucosamine hydrochloride using 0.26 mmol SnCl4·5H2O and 20 mL water. This corresponds to a yield of 59.4%. The SnCl4 forms SnO2 and HCl in solution and under similar conditions using SnO2 and HCl, chitosan formed 27.4 wt% LA.

Trihexyl(tetradecyl)phosphonium ionic liquids (ILs) are found to support the formation of Pd(0) nanoparticles without the addition of reducing agents such as NaBH4. The resulting particles are highly crystalline and have been characterized by a range of techniques including TEM and XRD. Their sizes are in the range 7 ± 2 nm. The particle formation process is highly dependent on the anion of the IL with no nanoparticles observed when the chloride derivative was used. Particle shape could be controlled through varying the anion of the IL and the Pd(II) precursor used. Palladium chloride reagents gave truncated octahedron shaped particles in trihexyl(tetradecyl)phosphonium dodecylbenzenesulfonate, whereas palladium acetate under the same conditions afforded a mixture of shapes including triangular plates. We propose that the presence of chloride anions in the reaction mixtures led to oxidative etching of the particles and that this process can be reduced in the presence of certain anion partners in the IL including bis(2,4,4-trimethylpentyl)phosphinate. Two possible reduction mechanisms based on reactions of the phosphonium cation are suggested for the formation of the Pd(0) species. The resulting nanoparticles are effective in catalyzing the Suzuki reaction of 4-bromotoluene and benzene boronic acid.

A group of 14 different bio-sourced, renewable feedstocks (homoserine, 1; glutamic acid, 2; aspartic acid, 3; 2,5-furandicarboxylic acid, 4; fumaric acid, 5; oxalacetic acid, 6; tartaric acid, 7; malic acid, 8; succinic acid, 9; levulinic acid, 10; γ-hydroxybutyrolactone, 11; xylitol, 12; mannitol, 13; sorbitol, 14) have been examined for their solubility/miscibility in a variety of ‘green’ solvents, including water, supercritical carbon dioxide (scCO2), and ionic liquids. Two other bio-based compounds 5-hydroxymethylfurfural, 15, and D-xylose, 16, were studied in selected solvents. Trends in solubility have been assessed so that these data may be extrapolated to help predict solubilities of other related compounds. For example, 10, 11 and 15 all demonstrated appreciable solubility in scCO2, as they possess weak intermolecular interactions. The dicarboxylic acids studied (4–9) all proved soluble in modified scCO2 (by use of MeOH as a cosolvent). While the polyols (12–14) and 1 were insoluble in scCO2 but water of various pHs and ionic liquids proved adept at their dissolution. Some of the amino acids studied (2 and 3) were only soluble in water with an adjustment of pH.

Metal complexes of polydimethylsiloxane-derived ligands can be adsorbed onto silica and subsequently reduced in-situ in supercritical CO2 (scCO2) to generate metal nanoparticles. Pd nanoparticles on silica, generated during C–C coupling reactions in scCO2, can be recycled several times without any loss in activity. Focusing on Heck and Suzuki coupling reactions, the products showed no contamination of the organic products with Pd using quantitative ICP emission spectroscopy. The use of scCO2 prevents the desorption of the Pd nanoparticles from their support. Build-up of ammonium salts as by-products in these coupling reactions leads to reduced activity for these heterogeneous catalysts after four runs.