Sustainable and eco-friendly strategies for shrimp shell valorization

Metabolic and Bioprocess Engineering of Clostridium tyrobutyricum for Butyl Butyrate Production on Xylose and Shrimp Shell Waste

Microbial conversion of agri-food waste to valuable compounds offers a sustainable route to develop the bioeconomy and contribute to sustainable biorefinery. Clostridium tyrobutyricum displays a series of native traits suitable for high productivity conversion of agri-food waste, which make it a promising host for the production of various compounds, such as the short-chain fatty acids and their derivative esters products. In this study, a butanol synthetic pathway was constructed in C. tyrobutyricum, and then efficient butyl butyrate production through in situ esterification was achieved by the supplementation of lipase into the fermentation. The butyryl-CoA/acyl-CoA transferase (cat1) was overexpressed to balance the ratio between precursors butyrate and butanol. Then, a suitable fermentation medium for butyl butyrate production was obtained with xylose as the sole carbon source and shrimp shell waste as the sole nitrogen source. Ultimately, 5.9 g/L of butyl butyrate with a selectivity of 100%, and a productivity of 0.03 g/L·h was achieved under xylose and shrimp shell waste with batch fermentation in a 5 L bioreactor. Transcriptome analyses exhibited an increase in the expression of genes related to the xylose metabolism, nitrogen metabolism, and amino acid metabolism and transport, which reveal the mechanism for the synergistic utilization of xylose and shrimp shell waste. This study presents a novel approach for utilizing xylose and shrimp shell waste to produce butyl butyrate by using an anaerobic fermentative platform based on C. tyrobutyricum. This innovative fermentation medium could save the cost of nitrogen sources (~97%) and open up possibilities for converting agri-food waste into other high-value products.

Maximizing crustaceans (shrimp, crab, and lobster) by-products value for optimum valorization practices: A comparative review of their active ingredients, extraction, bioprocesses and applications

BACKGROUND

The processing of the three major crustaceans (shrimp, lobster, and crab) is associated with inevitable by-products, high waste disposal costs, environmental and human health issues, loss of multiple biomaterials (chitin, protein hydrolysates, lipids, astaxanthin and minerals). Nowadays, these bioresources are underutilized owing to the lack of effective and standardized technologies to convert these materials into valued industrial forms.

AIM OF REVIEW

This review aims to provide a holistic overview of the various bioactive ingredients and applications within major crustaceans by-products. This review aims to compare various extraction methods in crustaceans by-products, which will aid identify a more workable platform to minimize waste disposal and maximize its value for best valorization practices.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The fully integrated applications (agriculture, food, cosmetics, pharmaceuticals, paper industries, etc.) of multiple biomaterials from crustaceans by-products are presented. The pros and cons of the various extraction methods, including chemical (acid and alkali), bioprocesses (enzymatic or fermentation), physical (microwave, ultrasound, hot water and carbonic acid process), solvent (ionic liquids, deep eutectic solvents, EDTA) and electrochemistry are detailed. The rapid development of corresponding biotechnological attempts present a simple, fast, effective, clean, and controllable bioprocess for the comprehensive utilization of crustacean waste that has yet to be applied at an industrial level. One feasible way for best valorization practices is to combine innovative extraction techniques with industrially applicable technologies to efficiently recover these valuable components.

Chitinous material bioconversion by three new chitinases from the yeast Mestchnikowia pulcherrima

BACKGROUND

Chitinases are widely distributed enzymes that perform the biotransformation of chitin, one of the most abundant polysaccharides on the biosphere, into useful value-added chitooligosaccharides (COS) with a wide variety of biotechnological applications in food, health, and agricultural fields. One of the most important group of enzymes involved in the degradation of chitin comprises the glycoside hydrolase family 18 (GH18), which harbours endo- and exo-enzymes that act synergistically to depolymerize chitin. The secretion of a chitinase activity from the ubiquitous yeast Mestchnikowia pulcherrima and their involvement in the post-harvest biological control of fungal pathogens was previously reported.

RESULTS

Three new chitinases from M. pulcherrima, MpChit35, MpChit38 and MpChit41, were molecularly characterized and extracellularly expressed in Pichia pastoris to about 91, 90 and 71 mU ml- 1, respectively. The three enzymes hydrolysed colloidal chitin with optimal activity at 45 ºC and pH 4.0-4.5, increased 2-times their activities using 1 mM of Mn2+ and hydrolysed different types of commercial chitosan. The partial separation and characterization of the complex COS mixtures produced from the hydrolysis of chitin and chitosan were achieved by a new anionic chromatography HPAEC-PAD method and mass spectrometry assays. An overview of the predicted structures of these proteins and their catalytic modes of action were also presented. Depicted their high sequence and structural homology, MpChit35 acted as an exo-chitinase producing di-acetyl-chitobiose from chitin while MpChit38 and MpChit41 both acted as endo-chitinases producing tri-acetyl-chitotriose as main final product.

CONCLUSIONS

Three new chitinases from the yeast M. pulcherrima were molecularly characterized and their enzymatic and structural characteristics analysed. These enzymes transformed chitinous materials to fully and partially acetylated COS through different modes of splitting, which make them interesting biocatalysts for deeper structural-function studies on the challenging enzymatic conversion of chitin.

Simultaneous Optimization of Deacetylation Degree and Molar Mass of Chitosan from Shrimp Waste

Shrimp waste is a valuable source for chitin extraction and consequently for chitosan preparation. In the process of obtaining chitosan, a determining step is the chitin deacetylation. The main characteristic of chitosan is the degree of deacetylation, which must be as high as possible. The molar mass is another important parameter that defines its utilizations, and according to these, high or low molar masses are required. The present study is an attempt to optimize the deacetylation step to obtain chitosan with a high degree of deacetylation and high or low molar mass. The study was carried out based on experimental data obtained in the frame of a central composite design where three working parameters were considered: NaOH concentration, liquid:solid ratio, and process duration. The regression models defined for the degree of deacetylation (DD) and for the mean molar mass (MM) of chitosan powders were used in the formulation of optimization problems. The objectives considered were simultaneous maximum DD and maximum/minimum MM for the final chitosan samples. For these purposes, multiobjective optimization problems were formulated and solved using genetic algorithms implemented in Matlab®. The multiple optimal solutions represented by trade-offs between the two objectives are presented for each case.

Current and Expected Trends for the Marine Chitin/Chitosan and Collagen Value Chains

Chitin/chitosan and collagen are two of the most important bioactive compounds, with applications in the pharmaceutical, veterinary, nutraceutical, cosmetic, biomaterials, and other industries. When extracted from non-edible parts of fish and shellfish, by-catches, and invasive species, their use contributes to a more sustainable and circular economy. The present article reviews the scientific knowledge and publication trends along the marine chitin/chitosan and collagen value chains and assesses how researchers, industry players, and end-users can bridge the gap between scientific understanding and industrial applications. Overall, research on chitin/chitosan remains focused on the compound itself rather than its market applications. Still, chitin/chitosan use is expected to increase in food and biomedical applications, while that of collagen is expected to increase in biomedical, cosmetic, pharmaceutical, and nutritional applications. Sustainable practices, such as the reuse of waste materials, contribute to strengthen both value chains; the identified weaknesses include the lack of studies considering market trends, social sustainability, and profitability, as well as insufficient examination of intellectual property rights. Government regulations, market demand, consumer preferences, technological advancements, environmental challenges, and legal frameworks play significant roles in shaping both value chains. Addressing these factors is crucial for seizing opportunities, fostering sustainability, complying with regulations, and maintaining competitiveness in these constantly evolving value chains.

Green Chemistry to Valorize Seafood Side Streams: An Ecofriendly Roadmap toward Sustainability

A major challenge facing sustainable seafood production is the voluminous amounts of nutrient-rich seafood side streams consisting of by-catch, processing discards, and process effluents. There is a lack of a comprehensive model for optimal valorization of the side streams. Upcoming green chemistry-based processing has the potential to recover diverse valuable compounds from seafood side streams in an ecofriendly manner. Microbial and enzymatic bioconversions form major green processes capable of releasing biomolecules from seafood matrices under mild conditions. Novel green solvents, because of their low toxicity and recyclable nature, can extract bioactive compounds. Nonthermal technologies such as ultrasound, supercritical fluid, and membrane filtration can complement green extractions. The extracted proteins, peptides, polyunsaturated fatty acids, chitin, chitosan, and others function as nutraceuticals, food supplements, additives, etc. Green processing can address environmental, economic, and technological challenges of valorization of seafood side streams, thereby supporting sustainable seafood production. Green processing can also encourage bioenergy production. Multiple green processes, integrated in a marine biorefinery, can optimize valorization on a zero-waste trade-off, for a circular blue economy. A green chemistry-based valorization framework has the potential to meet the Sustainable Development Goals (SDGs) of the United Nations.

Degradation of marine crustacean shell wastes through single-stage co-fermentation using proteolytic and chitinolytic bacteria

Management of crustacean shell waste (SW) through an eco-friendly technique is an environmental obligation to control pollution. The present study showed a novel approach through the simultaneous application of proteolytic and chitinolytic bacteria to effectively degrade unprocessed crustacean SW. For this, the bacteria with concurrent chitinolytic and proteolytic activity (Bacillus subtilis, Priestia megaterium, or Bacillus amyloliquefaciens) were applied either alone or in combination with one proteolytic strain (Paenibacillus alvei) in the unprocessed lobster, crab, and shrimp SW. The method degraded the shells with high deproteinization (> 90%) and demineralization efficiency (> 90%). The degradation was confirmed through scanning electron microscopy. The highest weight loss achieved with shrimp, crab, and lobster shells was 93.67%, 82.60%, and 83.33%, respectively. B. amyloliquefaciens + P. alvei combination produced the highest weight loss in crab and lobster SW, whereas all combinations produced statistically similar weight loss in shrimp SW. There was a concurrent production of N-acetyl glucosamine (up to 532.89, 627.87, and 498.95 mg/g of shrimp, lobster, and crab shell, respectively, with P. megaterium + P. alvei and B. amyloliquefaciens + P. alvei in all SW) and amino acids (4553.8, 648.89, 957.27 μg/g of shrimp, lobster, and crab shells, respectively with B. subtilis + P. alvei in shrimp and B. amyloliquefaciens + P. alvei in crab and lobster). Therefore, it is concluded that, for the first time, efficient degradation of crustacean shell waste was observed using chitinolytic and proteolytic bacterial fermentation with the obtention of byproducts, providing a basis for further application in SW management.

Facile fabrication of chitosan Schiff bases from giant tiger prawn shells (Penaeus monodon) via solvent-free mechanochemical grafting

Fabrication of chitosan Schiff bases (ChSB) from giant tiger prawn shells (Penaeus monodon) using an environmentally friendly method has been conducted successfully. Transformation of Prawn Shells (PS) as raw material into chitin then chitosan was executed under ambient temperature. Later, three Ch Schiff bases (ChSB-A, ChSB-S, and ChSB-V) were successfully synthesized for the first time via solvent-free mechanochemical grafting with 2-hydroxy benzaldehyde, 4-methoxy benzaldehyde, and 3-methoxy-4-hydroxy benzaldehyde, respectively. Synthesis was carried out with Shaker Mill-Ultimate Gravity equipped with a Teflon jar with zirconia balls; then the product was characterized. FTIR analysis proved the conversion of free amine to imine groups. The degree of substitution (DS) and crystallinity index (CrI) were determined by elemental analysis and X-ray diffraction. The DS values obtained were about 0.343, 0.795, and 0.055 for ChSB-A, ChSB-S, and ChSB-V, respectively. The CrI of ChSB-A, ChSB-S, and ChSB-V was 53.3, 51.7, and 46.9 %, respectively. The thermal gravimetric analysis showed that the mechanochemical grafting of Ch improves the thermal stability of ChSB. This developed method provides a novel potential technique to convert PS into ChSB products by solvent-free mechanochemical grafting.

Maximizing the potential of leachate from sewage sludge as a sustainable nutrients source to alleviate the fertilizer crisis

Leachate from separate digesters in biological wastewater treatment plants contains valuable biogenic compounds that can serve as fertilizer nutrients. In this study, a method was developed to utilize leachate from sewage sludge dewatering as a raw material for the preparation of a plant conditioner, providing water, nutrients, and growth-stimulating amino acids. A chemical conditioning procedure (65% HNO₃) was used to prepare the leachate solution for fertilization. The feasibility of producing an amino acid-based fertilizer using shrimp shells and inorganic acids (96% H₂SO₄ and 85% H₃PO₄) was also demonstrated. Microbiological analysis confirmed the safety of the formulations, and chelation of micronutrients with available amino acids was proven (up to 100% chelating degree). The bioavailability of all nutrients was confirmed through extraction tests (extraction in neutral ammonium citrate). Germination tests showed similar fresh plant masses to those with commercial preparations, demonstrating the effectiveness of the developed technology. This approach aligns with circular economy principles and sustainable development and contributes to mitigating the impacts of climate change.

Influence of pre-treatment and drying process of the shrimp (Litopenaeus vannamei) exoskeleton for balanced feed production

Shrimp industry wastes can be transformed and used as raw material for the development of new products. The aim of this research was to evaluate the influence of pre-treatment and drying process of the shrimp (Litopenaeus vannamei) exoskeleton for balanced feed production. The balanced feed was made with shrimp flour (25.74%), cotton seed cake (24.56%), rice bran (22.06%), beef tallow (16.18%), sweet potato flour (5.81%), and cassava flour (5.66%). To obtain the flour, shrimp processing waste (heads and exoskeletons) were blanched, dried, ground and sieved. Blanching was carried out using a full factorial 2² experimental design, where temperature and time were evaluated as independent variables. The drying kinetics of the blanched exoskeletons were performed in a tray dryer at different temperatures (40 and 50 °C) and air velocity (1, 1.5 and 2 m/s). The blanching process showed no significant effect on the protein content present in shrimp by-products. The drying kinetics showed that the greatest loss of moisture occurs in the period of decreasing velocity, dominated by mass transfer by diffusion. The Page model showed the best fit for the experimental data. From the mixture of shrimp flour with the other ingredients in the proportions indicated by the Solve software, fish food pellets were obtained. These met the nutritional requirements of fish (tarpon) in the juvenile-commercial stage.

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Insights into the relationships of modifying methods, structure, functional properties and applications of chitin: A review

Chitin as the second plentiful polysaccharide has arouse widely attention due to its remarkable availability and biocompatibility. While the strong inter/intra molecular hydrogen bonds and crystallinity severely restrict its applications. Recently, multiple emerging technologies are increasingly used to modify chitin structure for the sake of obtaining excellent functional properties, as well as broadening the corresponding applications. Firstly, this review systematically outlines the features of single and combined methods for chitin modification. Then, the impacts of various modifying methods on the structural characteristics of chitin, including molecular weight, degree of acetylation and functional groups, are further summarized. In addition, the effects of these structural characteristics on the functional properties as well as its potential related applications are illustrated. The conclusion of this review provides better understanding of the relationships among the modifying methods, structure, properties and applications, contributing to chitin modification for the targeted purpose in the future study.

Efficient removal of Tris(2-chloroethyl) phosphate by biochar derived from shrimp shell: Adsorption performance and mechanism study

Tris(2-chloroethyl) phosphate (TCEP) has been detected all over the world as a typical refractory organic phosphate, especially in groundwater. This work applied a calcium-rich biochar derived from shrimp shell as a low-cost adsorbent for TCEP removal. Based on the kinetics and isotherm studies, the adsorption of TCEP on biochar was monolayer adsorbed on a uniform surface, with SS1000 (the biochar was prepared at the carbonization temperature of 1000 °C) achieving the maximum adsorption capacity of 264.11 mg·g^-1. The prepared biochar demonstrated stable TCEP removal ability throughout a wide pH range, in the presence of co-existing anions, and in diverse water bodies. A rapid removal rate of TCEP was observed during the adsorption process. When the dosage of SS1000 was 0.2 g·L^-1, 95% of TCEP could be removed within the first 30 min. The mechanism analysis indicated that the calcium species and basic functional groups on the SS1000 surface were highly involved in the TCEP adsorption process.

Turning Food Protein Waste into Sustainable Technologies

For each kilogram of food protein wasted, between 15 and 750 kg of CO₂ end up in the atmosphere. With this alarming carbon footprint, food protein waste not only contributes to climate change but also significantly impacts other environmental boundaries, such as nitrogen and phosphorus cycles, global freshwater use, change in land composition, chemical pollution, and biodiversity loss. This contrasts sharply with both the high nutritional value of proteins, as well as their unique chemical and physical versatility, which enable their use in new materials and innovative technologies. In this review, we discuss how food protein waste can be efficiently valorized not only by reintroduction into the food chain supply but also as a template for the development of sustainable technologies by allowing it to exit the food-value chain, thus alleviating some of the most urgent global challenges. We showcase three technologies of immediate significance and environmental impact: biodegradable plastics, water purification, and renewable energy. We discuss, by carefully reviewing the current state of the art, how proteins extracted from food waste can be valorized into key players to facilitate these technologies. We furthermore support analysis of the extant literature by original life cycle assessment (LCA) examples run ad hoc on both plant and animal waste proteins in the context of the technologies considered, and against realistic benchmarks, to quantitatively demonstrate their efficacy and potential. We finally conclude the review with an outlook on how such a comprehensive management of food protein waste is anticipated to transform its carbon footprint from positive to negative and, more generally, have a favorable impact on several other important planetary boundaries.

Eco-design and tunable structure-properties of chitosan-epoxy-glycerol-silicate biohybrids using integrated crosslinking

Tunable structure-properties were achieved for chitosan-epoxy-glycerol-silicate (CHTGP) biohybrids, eco-designed via integrated amine-epoxy and waterborne sol-gel crosslinking reactions. Medium molecular weight chitosan (CHT), with 83 % degree of deacetylation was prepared by microwave-assisted alkaline deacetylation of chitin. The amine group of chitosan was covalently bonded to the epoxide of 3-glycidoxypropyltrimethoxysilane (G) for further crosslinking with a sol-gel derived glycerol-silicate precursor (P) from 0.5 % to 5 %. The impact of crosslinking density on the structural morphology, thermal, mechanical, moisture-retention and antimicrobial properties of the biohybrids were characterized by FTIR, NMR, SEM, swelling and bacterial inhibition studies and contrasted with a corresponding series (CHTP) without epoxy silane. Water uptake was significantly reduced in all biohybrids with a 12 % window of variation between the two series. Properties observed in biohybrids with only epoxy-amine (CHTG) or sol-gel crosslinking reactions (CHTP), were reversed in the integrated biohybrids (CHTGP) to impart improved thermal and mechanical stability and antibacterial activity.

Chemoenzymatic catalytic synthesis of furfurylamine from hemicellulose in biomasses

Recently, efficient synthesis of furan-based chemicals from biomacromolecule via chemoenzymatic approaches have been widely recognized. In this work, an efficient conversion of biomacromolecule (e.g., xylan in biomass) to furfurylamine (FLA) was developed in a tandem reaction by bridging with chemocatalysis and biocatalysis. Various biomasses (e.g., corncob, bagasse, bamboo shoot shell, corn stalk, rice straw stalk, reed, water bamboo and sunflower stalk) could produce different titer of furfural due to the diverse xylan content in biomass. After being catalyzed by shrimp shell-supported solid acid catalyst (Sn-DAT-SS) in deep eutectic solvent choline chloride:ethylene glycol (ChCl:EG) - water (10:90, v/v) at 170 °C after 30 min, corncob gave the highest furfural yield of 52.4 %. The potential catalytic mechanism for Sn-DAT-SS-catalyzing the conversion of biomass into furfural in ChCl:EG - water was proposed. It was found that by-products (formic acid, levulinic acid, 5-hydroxymethylfurfural) and soluble sugars (glucose, xylose, arabinose, cellobiose) produced during the conversion of biomass to furfural had certain inhibition effects on the biotransamination of furfural to FLA. Biomass-derived furfural (36.7-92.3 mM) could be fully aminated to FLA by E. coli CCZU-XLS160 cells harboring ω-transaminase after 24-72 h. The established chemoenzymatic strategy for converting biomacromolecules into valuable furan-based products was successfully developed in an eco-friendly system.

Fermented shellfish condiments: A comprehensive review

Fermented shellfish condiments are globally consumed especially among Asian countries. Condiments, commonly used as flavor enhancers, have unique sensory characteristics and are associated with umami and meaty aroma. The main reactions that occur during fermentation of shellfish include proteolysis by endogenous enzymes and microbial activities to produce peptides and amino acids. The actions of proteolytic enzymes and microorganisms (predominantly bacteria) are found to be largely responsible for the formation of taste and aroma compounds. This review elaborates different aspects of shellfish fermentation including classification, process, substrates, microbiota, changes in both physicochemical and biochemical components, alterations in nutritional composition, flavor characteristics and sensory profiles, and biological activities and their undesirable impacts on health. The characteristics of traditional shellfish production such as long duration and high salt concentration not only limit nutritional value but also inhibit the formation of toxic biogenic amines. In addition, this review article also covers novel bioprocesses such as low salt fermentation and use of novel starter cultures and/or novel enzymes to accelerate fermentation and produce shellfish condiments that are of better quality and safer for consumption. Practical Application: The review paper summarized the comprehensive information on shellfish fermentation to provide alternative strategies to produce shellfish comdiments that are of better quality and safer for consumption.

Development of Fermented Shrimp Shell Product with Hypoglycemic and Hypolipidemic Effects on Diabetic Rats

In 2020, approximately 9.3 billion tons of crustaceans were consumed, and 45–48% of shrimp shell (SS) by-products were discarded as waste. In this study, the SS of Litopenaeus vannamei was fermented by Lactobacillus plantarum LV33204, Stenotrophomonas maltophilia LV2122 (strong proteolytic activity), and Aeromonas dhakensis LV1111 (chitin-degrading activity), and the optimal fermentation conditions of liquid-fermented SS was established. Contents of total peptide, astaxanthin, and total phenolic content of the fermented SS were significantly higher than that of unfermented SS. In the presence of fermented SS, glucose uptake and insulin resistance of TNF-α-stimulated FL83B hepatocytes were markedly improved. Furthermore, daily oral supplement of fermented SS to streptozotocin (STZ)/nicotinamide (NA)-induced diabetic rats for 7 weeks significantly reduced plasma glucose and insulin resistance. Meanwhile, ingestion of fermented SS might enhance hepatic catabolism of glucose by increasing hexokinase and glucose-6-phosphate dehydrogenase activity and decreasing glucose-6-phosphatase activity. In addition, the fermented SS downregulated plasma total cholesterol (TG), triglycerides (TCs), low-density lipoprotein cholesterol (LDL-C), liver TG, and TC and lipid peroxidation levels in diabetic rats. In conclusion, a biorefinery process for waste SS was established through mixed strain fermentation. The in vitro and in vivo data reveal that the fermented SS is a promising functional food for the management of diabetic hyperglycemia and hyperlipidemia.

Mechano-Enzymatic Degradation of the Chitin from Crustacea Shells for Efficient Production of N-acetylglucosamine (GlcNAc)

Chitin, the second richest polymer in nature, is composed of the monomer N-acetylglucosamine (GlcNAc), which has numerous functions and is widely applied in the medical, food, and chemical industries. However, due to the highly crystalline configuration and low accessibility in water of the chitin resources, such as shrimp and crab shells, the chitin is difficult utilize, and the traditional chemical method causes serious environment pollution and a waste of resources. In the present study, three genes encoding chitinolytic enzymes, including the N-acetylglucosaminidase from Ostrinia furnacalis (OfHex1), endo-chitinase from Trichoderma viride (TvChi1), and multifunctional chitinase from Chitinolyticbacter meiyuanensis (CmChi1), were expressed in the Pichia pastoris system, and the positive transformants with multiple copies were isolated by the PTVA (post-transformational vector amplification) method, respectively. The three recombinants OfHex1, TvChi1, and CmChi1 were induced by methanol and purified by the chitin affinity adsorption method. The purified recombinants OfHex1 and TvChi1 were characterized, and they were further used together for degrading chitin from shrimp and crab shells to produce GlcNAc through liquid-assisted grinding (LAG) under a water-less condition. The substrate chitin concentration reached up to 300 g/L, and the highest yield of the product GlcNAc reached up to 61.3 g/L using the mechano-enzymatic method. A yield rate of up to 102.2 g GlcNAc per 1 g enzyme was obtained.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Recycling phosphorus and calcium from aquaculture waste as a precursor for hydroxyapatite (HAp) production: a review

Water contaminated with phosphorus needs to be managed efficiently to ensure that clean water sources will be preserved. Aquaculture plays an essential role in supplying food and generating high revenue. However, the quantity of phosphorus released from aquaculture effluents is among the major concerns for the environment. Phosphorus is a non-renewable, spatially concentrated material essential for global food production. Phosphorus is also known as a primary source of eutrophication. Hence, phosphorus recovery and separation from different wastewater streams are mandatory. This paper reviews the source of phosphorus in the environment, focusing on aquaculture wastewater as a precursor for hydroxyapatite formation evaluates the research progress on maximizing phosphorus removal from aquaculture wastewater effluents and converting it into a conversion. Shrimp shell waste appears to be an essential resource for manufacturing high-value chemicals, given current trends in wealth creation from waste. Shrimp shell waste is the richest source of calcium carbonate and has been used to produce hydroxyapatite after proper treatment is reviewed. There have been significant attempts to create safe and long-term solutions for the disposal of shrimp shell debris. Through the discussion, the optimum condition of the method, the source of phosphorus, and the calcium are the factors that influence the formation of hydroxyapatite as a pioneer in zero-waste management for sustainability and profitable approach. This review will provide comprehensive documentation on resource utilization and product development from aquaculture wastewater and waste to achieve a zero-waste approach.

Sustainable processes for treatment and management of seafood solid waste

Seafood processing is an important economical activity worldwide and is an integral part of the food chain system. However, their processing results in solid waste generation whose disposal and management is a serious concern. Proteins, amino acids, lipids with high amounts of polyunsaturated fatty acids (PUFA), carotenoids, and minerals are abundant in the discards, effluents, and by-catch of seafood processing waste. As a result, it causes nutritional loss and poses major environmental risks. To solve the issues, it is critical that the waste be exposed to secondary processing and valorization for recovery of value added products. Although chemical waste treatment technologies are available, the majority of these procedures have inherent flaws. Biological solutions, on the other hand, are safe, efficacious, and ecologically friendly while maintaining the intrinsic bioactivities after waste conversion. Microbial fermentation or the actions of exogenously introduced enzymes on waste components are used in most bioconversion processes. Algal biotechnology has recently developed unique technologies for biotransformation of nutrients, which may be employed as a feedstock for the recovery of important chemicals as well as biofuel. Bioconversion methods combined with a bio-refinery strategy offer the potential to enable environmentally-friendly and cost-effective seafood waste management. The refinement of these wastes through sustainable bioprocessing interventions can give rise to various circular bioeconomies within the seafood processing sector. Moreover, a techno-economic perspective on the developed solid waste processing lines and its subsequent environmental impact could facilitate commercialization. This review aims to provide a comprehensive view and critical analysis of the recent updates in seafood waste processing in terms of bioconversion processes and byproduct development. Various case studies on circular bioeconomy formulated on seafood processing waste along with techno-economic feasibility for the possible development of sustainable seafood biorefineries have also been discussed.

Efficient production of GlcNAc in an aqueous-organic system with a Chitinolyticbacter meiyuanensis SYBC-H1 mutant

OBJECTIVES

Shellfish waste is a primary source for making N-acetyl-D-glucosamine. Thus, establishing a high-efficiency and low-cost bioconversion method to produce N-acetyl-D-glucosamine directly from shellfish waste was promising.

RESULTS

A mutant C81 was obtained from Chitinolyticbacter meiyuanensis SYBC-H1 via ⁶⁰Co-γ irradiation. This mutant C81 showed the highest chitinase activity of 9.8 U/mL that was 85% higher than the parent strain. The mutant C81 exhibted improved antioxidant activities, including total antioxidant capacity, superoxide radical ability, and hydroxyl radical scavenging ability, compared to that of the parent strain. Four out of nine organic solvents increased the chitinase activity by 1.9%, 6.8%, 11.7%, and 15.8%, corresponding to methylbenzene, n-heptane, petroleum ether, and n-hexane, respectively. The biphase system composed of aqueous and hexane presented a five-fold reduction of cell viability compared to the control. Using a continuous fermentation bioconversion process, 4.2 g/L GlcNAc was produced from crayfish shell powder with a yield of 80% of the chitin content.

CONCLUSIONS

This study demonstrated that the mutant C81 is suitable for converting crayfish shell powder into GlcNAc in an aqueous-organic system.

Pilot-scale co-processing of lignocellulosic biomass, algae, shellfish waste via thermochemical approach: Recent progress and future directions

Thermal co-processing of lignocellulosic and aquatic biomass, such as algae and shellfish waste, has shown synergistic effects in producing value-added energy products with higher process efficiency than the traditional method, highlighting the importance of scaling up to pilot-scale operations. This article discusses the design and operation of pilot-scale reactors for torrefaction, pyrolysis, and gasification, as well as the key parameters of co-processing biomass into targeted and improved quality products for use as fuel, agricultural application, and environmental remediation. Techno-economic analysis reveals that end product selling price, market dynamics, government policies, and biomass cost are crucial factors influencing the sustainability of thermal co-processing as a feasible approach to utilize the biomass. Because of its simplicity, pyrolysis allows greater energy recovery, while gasification has the highest net present value (profitability). Integration of liquefaction, hydrothermal, and fermentation pre-treatment technology has the potential to increase energy efficiency while reducing process residues.

Chitooligosaccharides production from shrimp chaff in chitosanase cell surface display system

Chitin refers to a natural biopolymer, which is economically significant to next-generation biorefineries. In this study, a novel high-yield method with cell surface-display chitosanase (CHI-1) was built to produce chitooligosaccharides (COS) from shrimp chaff through the co-fermentation in the presence of Bacillus subtilis and Acetobacter sp. Under the optimized co-fermentation conditions (5 g/L yeast extracts, 10 g/L KH₂PO₄, 6% ethanol, 50 g/L glucose), the final deproteinization (DP) and demineralization (DM) efficiency and the chitin yield were achieved as 94, 92 and 18%, respectively. The engineered E. coli BL21-pET23b(+)-NICHI maintained 81% of the initial enzyme activity after 40 days at room temperature. The crude CHI-1 was inactivated after one-day interacting with prepared chitosan. Moreover, E. coli BL21-pET23b(+)-NICHI still maintained excellent hydrolysis ability in 7 days, and the COS yield reached 41%. Accordingly, the proposed method exhibited excellent stability and a high hydrolysis efficiency to produce COS with whole engineered cells.

Microbial decomposition of crustacean shell for production of bioactive metabolites and study of its fertilizing potential

Crustacean shell waste disposal is considered as biggest problem in seafood processing centers. Incineration and landfilling are the commonest ways of disposal of the waste which causes environmental pollution. Microbial bio-conversion is one of the promising approaches to minimize the wastes by utilizing the same for deriving different value added metabolites. In this perspective, chitinase- and protease-producing bacterial strains were isolated from shrimp culture pond, and the potent isolate was subsequently identified as Alcaligenes faecalis SK10. Fermentative optimization of the production of chitinase (85.42 U/ml), protease (58.57 U/ml), and their catalytic products, viz., N-acetylamino sugar (84 μg/ml) and free amino acids (112 μg/ml), were carried out by utilizing shrimp and crab shell powder as principal substrate. The fermented hydrolysate (FH) was subsequently applied to evaluate its potential to be a candidate fertilizer for the growth of leguminous plant Pisum sativum and Cicer arietinum, and the results were compared with chitin, chitosan, and commercial biofertilizer amended group. The results revealed that FH have paramount potential to improve plants morpho-physiological parameters like stem and root length, chlorophyll, cellular RNA, protein content, and soil physico-chemical parameters like total nitrogen, magnesium, calcium, phosphorus, and potassium significantly (p < 0.05). Moreover, the application of FH also selectively encouraged the growth of free-living nitrogen-fixing bacteria, Rhizobium, phosphate-solubilizing bacteria in the soil by 4.82- and 5.27-, 5.57- and 4.71, and 7.64- and 6.92-fold, respectively, in the rhizosphere of P. sativum and C. arietinum, which collectively is a good sign for an ideal biofertilizer. Co-supplementation of FH with commercial PGPR-biofertilizer significantly influenced the morpho-physiological attributes of plant and physico-chemical and microbial attributes of soil. The study validated proficient and sustainable utilization of fermented hydrolysate of waste crustacean shell as biofertilizer.

A Simple One-Step Modification of Shrimp Shell for the Efficient Adsorption and Desorption of Copper Ions

Removing toxic heavy metal species from aqueous solutions is a point of concern in our society. In this paper, a promising biomass adsorbent, the modified waste shrimp shell (MS), for Cu (II) removal was successfully prepared using a facile and simple one-step modification, making it possible to achieve high-efficiency recycling of the waste NaOH solution as the modification agent. The outcome shows that with the continuous increase in pH, temperature and ion concentration, the adsorption effect of MS on Cu (II) can also be continuously improved. Adsorption isotherm and adsorption kinetics were fitted with the Langmuir isotherm model and the pseudo-second-order model, respectively, and the maximum adsorption capacity of Cu (II) as obtained from the Langmuir isotherm model fitting reached 1.04 mmol/g. The systematic desorption results indicated that the desorption rate of Cu (II) in the MS could reach 100% within 6 min, where HNO3 is used as the desorption agent. Moreover, experiments have proven that after five successive recycles of NaOH as a modifier, the adsorption capacity of MS on Cu (II) was efficient and stable, maintaining tendency in 0.83-0.85 mmol/g, which shows that waste NaOH solution can be used as a modification agent in the preparation of waste shrimp shell adsorbent, such as waste NaOH solution produced in industrial production, thereby making it possible to turn waste into renewable resources and providing a new way to recycle resources.

Chitosan-tripolyphosphate nanoparticles designed to encapsulate polyphenolic compounds for biomedical and pharmaceutical applications - A review

Plant-based polyphenols are natural compounds, present in fruits and vegetables. During recent years, polyphenols have gained special attention due to their nutraceutical and pharmacological activities for the prevention and treatment of human diseases. Nevertheless, their photosensitivity and low bioavailability, rapid metabolism and short biological half-life represent the major limitations for their use, which could be overcome by polyphenols encapsulation (flavonoids and non-flavonoids) into chitosan (CS)-tripolyphosphate (TPP) based nanoparticles (NP). In this review, we particularly focused on the ionic gelation method for the NP design. This contribution exhaustively discusses and compares results of scientific reports published in the last decade referring to ionic gelation applied for the protection, controlled and site-directed delivery of polyphenols. As a consequence, CS-TPP NP would constitute true platforms to transport polyphenols, or a combination of them, to be used for the designing of a new generation of drugs or nutraceuticals.

Enzymatic approaches in the bioprocessing of shellfish wastes

Several tonnes of shellfish wastes are generated globally due to the mass consumption of shellfish meat from crustaceans like prawn, shrimp, lobster, crab, Antarctic krill, etc. These shellfish wastes are a reservoir of valuable by-products like chitin, protein, calcium carbonate, and pigments. In the present scenario, these wastes are treated chemically to recover chitin by the chitin and chitosan industries, using hazardous chemicals like HCl and NaOH. Although this process is efficient in removing proteins and minerals, the unscientific dumping of harmful effluents is hazardous to the ecosystem. Stringent environmental laws and regulations on waste disposal have encouraged researchers to look for alternate strategies to produce near-zero wastes on shellfish degradation. The role of enzymes in degrading shellfish wastes is advantageous yet has not been explored much, although it produces bioactive rich protein hydrolysates with good quality chitin. The main objective of the review is to discuss the potential of various enzymes involved in shellfish degradation and their opportunities and challenges over chemical processes in chitin recovery.

A Hybrid Methodology to Minimize Freshwater Consumption during Shrimp Shell Waste Valorization Combining Multi-Contaminant Pinch Analysis and Superstructure Optimization

The conservation and proper management of natural resources constitute one of the main objectives of the 2030 Agenda for Sustainable Development designed by the Member States of the United Nations. In this work, a hybrid strategy based on process integration is proposed to minimize freshwater consumption while reusing wastewater. As a novelty, the strategy included a heuristic approach for identifying the minimum consumption of freshwater with a preliminary design of the water network, considering the concept of reuse and multiple pollutants. Then, mathematical programming techniques were applied to evaluate the possibilities of regeneration of the source streams through the inclusion of intercept units and establish the optimal design of the network. This strategy was used in the shrimp shell waste process to obtain chitosan, where a minimum freshwater consumption of 277 t/h was identified, with a reuse strategy and an optimal value of US $5.5 million for the design of the water network.