Using waste biomass to produce 3D-printed artificial biodegradable structures for coastal ecosystem restoration

The loss of ecosystem functions and services caused by rapidly declining coastal marine ecosystems, including corals and bivalve reefs and wetlands, around the world has sparked significant interest in interdisciplinary methods to restore these ecologically and socially important ecosystems. In recent years, 3D-printed artificial biodegradable structures that mimic natural life stages or habitat have emerged as a promising method for coastal marine restoration. The effectiveness of this method relies on the availability of low-cost biodegradable printing polymers and the development of 3D-printed biomimetic structures that efficiently support the growth of plant and sessile animal species without harming the surrounding ecosystem. In this context, we present the potential and pathway for utilizing low-cost biodegradable biopolymers from waste biomass as printing materials to fabricate 3D-printed biodegradable artificial structures for restoring coastal marine ecosystems. Various waste biomass sources can be used to produce inexpensive biopolymers, particularly those with the higher mechanical rigidity required for 3D-printed artificial structures intended to restore marine ecosystems. Advancements in 3D printing methods, as well as biopolymer modifications and blending to address challenges like biopolymer solubility, rheology, chemical composition, crystallinity, plasticity, and heat stability, have enabled the fabrication of robust structures. The ability of 3D-printed structures to support species colonization and protection was found to be greatly influenced by their biopolymer type, surface topography, structure design, and complexity. Considering limited studies on biodegradability and the effect of biodegradation products on marine ecosystems, we highlight the need for investigating the biodegradability of biopolymers in marine conditions as well as the ecotoxicity of the degraded products. Finally, we present the challenges, considerations, and future perspectives for designing tunable biomimetic 3D-printed artificial biodegradable structures from waste biomass biopolymers for large-scale coastal marine restoration.

Chemical extraction of chitin from American lobster (Homarus americanus) shells optimized through response surface methodology

Chitin extraction from the shells of American lobsters (Homarus americanus) was optimized through the use of response surface methodology (RSM). The demineralization step was optimized to minimize the ash content of shell samples and the deproteination step was optimized to minimize the protein content of the chitin product. At a laboratory scale, one set of optimized conditions for the demineralization step was 7.35 % w/w acetic acid at a 40 mL/g of powdered lobster shell ratio for 15 min; this lowered the ash content from 39.62 % to 0.41 ± 0.08 %. A set of optimized conditions for the deproteination step at a similar scale was 4 % w/w sodium hydroxide at a 43 mL/g demineralized shell ratio heated to 95 °C for 83 min. These conditions were indicated to entirely remove protein from the resultant chitin. Average yields under optimized conditions were 23.43 ± 1.75 % for demineralization and 30.33 ± 0.02 % for deproteination, though a demineralization reaction with larger biomass input had a higher yield at 40.31 %.

Chitin and chitin-based biomaterials: A review of advances in processing and food applications

Chitin is the most abundant natural amino polysaccharide, showing various practical applications owing to its functional properties. However, there are barriers in the development due to the difficulty of chitin extraction and purification, regarding its high crystallinity and low solubility. In recent years, some novel technologies such as microbial fermentation, ionic liquid, electrochemical extraction have emerged for the green extraction of chitin from new sources. Furthermore, nanotechnology, dissolution systems and chemical modification were applied to develop a variety of chitin-based biomaterials. Remarkably, chitin was used in delivering active ingredients and developing functional foods for weight loss, lipid reduction, gastrointestinal health, and anti-aging. Moreover, the application of chitin-based materials was expanded into medicine, energy and the environment. This review outlined the emerging extraction methods and processing routes of different chitin sources and advances in applying chitin-based materials. We aimed to provide some direction for the multi-disciplinary production and application of chitin.

Chitin, Chitosan, and Nanochitin: Extraction, Synthesis, and Applications

Crustacean shells are a sustainable source of chitin. Extracting chitin from crustacean shells is ongoing research, much of which is devoted to devising a sustainable process that yields high-quality chitin with minimal waste. Chemical and biological methods have been used extensively for this purpose; more recently, methods based on ionic liquids and deep eutectic solvents have been explored. Extracted chitin can be converted into chitosan or nanochitin. Once chitin is obtained and modified into the desired form, it can be used in a wide array of applications, including as a filler material, in adsorbents, and as a component in biomaterials, among others. Describing the extraction of chitin, synthesis of chitosan and nanochitin, and applications of these materials is the aim of this review. The first section of this review summarizes and compares common chitin extraction methods, highlighting the benefits and shortcomings of each, followed by descriptions of methods to convert chitin into chitosan and nanochitin. The second section of this review discusses some of the wide range of applications of chitin and its derivatives.