Subcritical Water Hydrolysis Research Articles

Subcritical water hydrolysis of soybean hulls pretreated by steam explosion: High pressure integrated process strategy

Steam explosion (SE) pretreatment and sequentially subcritical water hydrolysis (SWH) was studied. Industrially, there is an advantage in using this process strategy, since it uses the same equipment and instrumentation, without the need to transport the raw material in separate stages. The influence of severity factors (SF) (2.75, 3.05, and 3.35) and solvent used (distilled water and 0.5 % w/w of H2SO4) were evaluated in the SE efficiency. SWH was perform in integrated processing using the best pre-treatment conditions. The influence of temperature (230 and 260 °C) and the solvent/feed ratio (40 and 80) were considered. The integrated system resulted in a FS yield of 19.19 ± 0.49 g/ 100 g SH, for a condition Integrated 230 °C, S/F-40, a FS yield 3.3 times greater than that obtained in the same condition with untreated soybean hulls, demonstrating the advantage of perform the process under this operating strategy (SE + SWH)

Investigation of Coffee Instant Premium by Subcritical Water Hydrolysis: Enhance of Caffeine and Antioxidant Contents

The current study observed a basic investigation into instant coffee production through subcritical water (SBW) hydrolysis. A series of SWB research in lab-scale were carried out to optimize the product qualities by adjusting the process parameters such as temperature, solvent amounts, and time for hydrolysis. The caffeine, antioxidant, pH changes, and morphologies of modified and unmodified coffee powder (commercial products) were also evaluated by SEM. The result showed that the optimum conditions were observed for SBW process at 170°C/11.18 ml/20 min with obtained 0.48 mg/ml and 29.40 µg/ml for antioxidant and caffeine, respectively. SEM images represented physical degradation of coffee extracted powder during hydrolysis. Further, the amount of coffee in the blend with mineral amount could be important sources of minerals to the human diet, as evident by EDX analysis. Further, the change of chemistry surface was also confirmed by FTIR. In summary, flow-through SBW hydrolysis of coffee extract promises for enhance caffeine and antioxidant.

Protein Hydrolysates from Salmon Heads and Cape Hake By-Products: Comparing Enzymatic Method with Subcritical Water Extraction on Bioactivity Properties.

Fish by-products can be converted into high-value-added products like fish protein hydrolysates (FPHs), which have high nutritional value and are rich in bioactive peptides with health benefits. This study aims to characterise FPHs derived from salmon heads (HPSs) and Cape hake trimmings (HPHs) using Alcalase for enzymatic hydrolysis and Subcritical Water Hydrolysis (SWH) as an alternative method. All hydrolysates demonstrated high protein content (70.4-88.7%), with the degree of hydrolysis (DH) ranging from 10.7 to 36.4%. The peptide profile of FPHs indicated the breakdown of proteins into small peptides. HPSs showed higher levels of glycine and proline, while HPHs had higher concentrations of glutamic acid, leucine, threonine, and phenylalanine. Similar elemental profiles were observed in both HPHs and HPSs, and the levels of Cd, Pb, and Hg were well below the legislated limits. Hydrolysates do not have a negative effect on cell metabolism and contribute to cell growth. HPSs and HPHs exhibited high 2,2'-azino-bis(3 ethylbenzthiazoline-6)-sulfonic acid (ABTS) radical scavenging activity, Cu2+ and Fe2+ chelating activities, and angiotensin-converting enzyme (ACE) inhibitory activity, with HPHs generally displaying higher activities. The α-amylase inhibition of both FPHs was relatively low. These results indicate that HPHs are a promising natural source of nutritional compounds and bioactive peptides, making them potential candidates for use as an ingredient in new food products or nutraceuticals. SWH at 250 °C is a viable alternative to enzymatic methods for producing FPHs from salmon heads with high antioxidant and chelating properties.

Synergistic Effects of Azospirillum brasilense and Nitrogen Doses on Wheat Flour Characteristics and Yields of Reducing Sugars Obtained by Subcritical Water Hydrolysis from Bran

The synergistic interactions between nitrogen doses and microbial inoculation in crops indicate the potential for integrated nutrient management strategies in plant cultivation. Therefore, this study investigated the interactive effects of nitrogen doses and Azospirillum brasilense inoculation on wheat flour characteristics in terms of the falling number and color parameters and yields of reducing sugars obtained by subcritical water hydrolysis (SWH) from wheat bran. The strip-plot experimental design, bifactorial with three replications, was applied. Factor A was three wheat cultivars: ORS Agile (AGI), ORS Feroz (FER), and TSZ Dominadore (DOM). Factor D was five nitrogen doses in the topdressing: 0, 20, 40, 60, and 80 kg ha−1. The lowest value of falling number of 332 s was achieved with flour from FER cultivar using a nitrogen dose of 80 kg ha−1 with A. brasilense inoculation. The SWH produced yields of reducing sugars (YRS) from wheat bran of up to 6.74 ± 0.18 g (100 g of wheat bran)−1 for the cultivar DOM when using a nitrogen dose of 60 kg ha−1 associated with A. brasilense inoculation. In this cultivation condition, the falling number was 408 s and the color parameters were L* of 92.49, a* of −0.26, and b* of 11.91. In the other conditions, the YRS ranged from 2.93 ± 0.63 to 6.52 ± 0.04 g (100 g of wheat bran)−1. Both flour and bran are nutritional products with high application potential, and this study indicated SWH as a promising technique to dissociate the lignocellulosic complex of wheat bran without using hazardous solvents.

Fractionation and refining of pectic oligosaccharides derived from onion skins through continuous feed diafiltration

In this work, a diafiltration-based process was investigated for the recovery of pectic oligosaccharides produced by subcritical water hydrolysis from onion skin waste. Four tubular ceramic membranes from 100 to 1 kDa were selected based on the molecular weight of the different galacturonic acid species present in the onion skin hydrolysate. All these membranes showed high selectivity towards pectic oligosaccharides, with low retention for free galacturonic acid, monosaccharides, organic acids, and other impurities. The 50 and 100 kDa membranes completely retained pectic oligosaccharides with a molecular weight exceeding 80 kDa, accounting for approximately 30 % of the initial pectic oligosaccharides in the hydrolysate. However, the purification rate was significantly slower using the 50 kDa membrane due to the increased cake layer resistance. Furthermore, it was examined a fractionation/purification cascade involving sequential diafiltration stages using 100, 10, and 1 kDa membranes at 25 °C, TMP = 1 bar, and a crossflow velocity of 1.5 m s−1. Approximately 87 % of the initial pectic oligosaccharides were successfully recovered and purified in the retentates, highlighting their potential for diverse applications due to their narrow molecular weight distribution, while phenolic compounds and other valuable low molecular weight molecules were recovered in the final permeate.

Optimization of Ultrasound-enhanced Subcritical Water Hydrolysis of Oil Palm Empty Fruit Bunch for the Production of Fermentable Sugar

To enhance the hydrolysis to produce fermentable sugar, oil palm empty fruit bunch (OPEFB) has undergone ultrasonication pretreatment prior to subjection to subcritical water hydrolysis. This work aims to optimize the effect of temperature, reaction time, and the concentration of sodium dodecyl sulfate (SDS) as the surfactant, with the primary aim of maximizing sugar production in the subcritical water hydrolysis process applied to oil palm empty fruit bunch (OPEFB). The pretreatment process conditions were optimized using response surface methodology of the central composite design (RSM–CCD). The experimental design includes three factors and levels, with a range of 180–220 °C temperature (X1), 60–80 minutes process time (X2), and 1–5% w/w SDS concentration (X3), an α value of 1.68, and reducing sugar concentration (g/L) as response (Y1). The optimum condition for subcritical water hydrolysis of OPEFB was obtained at 208 °C, 78 minutes, and 2.6% w/w SDS concentration with an expected yield of 6.09 g/L. As a result, reducing sugar produced by enzymatic hydrolysis increased by 324.7% compared to raw OPEFB, with sugar yield of 45.64% after 36 hours. Along these, changes in crystallinity, chemical composition, lignocellulosic functional groups, and morphology were analyzed to determine the impact of the pre-treatment on OPEFB.

Potential of Subcritical Water Hydrolysis to Valorize Low-Valued Ray-Finned Fish (Labeobarbus nedgia): Effects of Hydrolysis Temperature and Pressurization Agent.

Subcritical water (SCW) hydrolysis was applied to valorize the low-valued ray-finned fish (Labeobarbus nedgia) into valuable protein hydrolysates, employing N2 and CO2 as pressurization agents at varying temperatures (140, 160, 180, and 200 °C). The degree of hydrolysis (DH) and total free amino acid content increased with temperature for both pressurizing agents. The highest DH (54.5 ± 0.4%) and total free amino acid content (210 ± 1 mg/gprot) were observed at 200 °C when CO2 gas was used as the pressurizing agent. Predominantly, glycine and alanine were released for both pressurizing agents. The antioxidant activity, evaluated through three different assays, increased with temperature and was found to be the highest at 200 °C. This study illustrated the advantages of the intensified SCW technology by using CO2 as a pressurization agent in valorizing low-valued ray-finned fish (Labeobarbus nedgia), as animal residue rich in proteins, for the production of valuable protein hydrolysates with a high fraction of valuable free amino acids, which could offer potential applications as a functional ingredient in the food industry.

Protein and Polysaccharide Recovery from Shrimp Wastes by Natural Deep Eutectic Solvent Mediated Subcritical Water Hydrolysis for Biodegradable Film.

Environmental pollution is a significant problem due to the improper disposal of plastics and shrimp shells outdoors. Therefore, the synthesis of biodegradable film from waste materials is highly important. The novelty of this research lies in the extraction of protein hydrolysates and chitosan from shrimp shells, as well as the fabrication of biodegradable film from these materials. In this study, the composite films were produced using the solution casting method. Moreover, the combined effect of ultrasound pretreatments (UPT) and natural deep eutectic solvents (NADES) was investigated as extraction media, to determine their potential impact on shrimp waste subcritical water hydrolysis (SWH). Shrimp shells were submitted to UPT in NADES solution, followed by SWH at different temperatures ranging from 150 to 230°C under 3MPa for 20min. Then, the physiochemical properties and bioactivities of the hydrolysates were assessed to determine their suitability for use in biodegradable packaging films. Additionally, the physiochemical properties and bioactivities of the resulting hydrolysates were also analyzed. The highest amount of protein (391.96 ± 0.48mg BSA/g) was obtained at 190°C/UPT/NADES, and the average molecular size of the protein molecules was less than 1000Da with different kinds of peptide. Overall, combined UPT and SWH treatments yielded higher antioxidant activity levels than individual treatments. Finally, the application of composite films was evaluated by wrapping fish samples and assessing their lipid oxidation. The use of higher concentrations of protein hydrolysates significantly delayed changes in the samples, thereby demonstrating the film's applicability.

Characterization of Acid-Mechanical Milling Pretreated Rice Straw for Subcritical Water Hydrolysis

Characterization of Acid-Mechanical Milling Pretreated Rice Straw for Subcritical Water Hydrolysis

Characterization of temperature-dependent subcritical water hydrolysis pattern of strong and floury rice cultivars and potential utilizations of their hydrolysates

This study investigated the effects of subcritical water (SW) temperatures on the hydrolysis pattern and characteristics of hydrolysates prepared with strong rice (SR) and floury rice (FR). The characteristics of the hydrolysates were generally dependent on the rice cultivar in the SW temperature range of 150–250 °C, while the cultivar dependence was diminished at temperatures greater than 300 °C. Based on brix and reducing sugar content, an optimal production of rice hydrolysates was obtained at a SW temperature range of 200–250 °C. However, thermal conversion of sugar into acids, 5-hydroxymethylfurfural (HMF) and furfural was manifested at 250 °C. The rice hydrolysates prepared at 250 ∼ 300 °C had the highest antioxidant activity with strong umami intensity, but they suppressed the growth of prebiotics. Therefore, the present study demonstrated that controlling the SW temperature is crucial to improve rice hydrolysis efficiency and to regulate the physiological activity of the hydrolysates.

Production of chitosan from shrimp shell using ultrasound followed by subcritical water hydrolysis

The interest in shrimp shell valorization has been growing in line with sustainability goals. Therefore, the main objective of this study was to obtain chitosan from shrimp shell using ultrasound followed by subcritical water treatment. Ultrasonication of shells was performed at 600 and 1200 W for 5 min. Then, shells were hydrolyzed at 140–260 °C and 50 bar for 10–60 min followed by demineralization using citric acid, bleaching using hydrogen peroxide and deacetylation using sodium hydroxide solution. The highest deproteination (80.93 %) was obtained by ultrasonication at 1200 W/5 min followed by subcritical water hydrolysis at 260 °C/50 bar/60 min, where the residue with a yield of 10.56 %, whiteness index of 60.42, degree of deacetylation of 64.27 %, relative crystallinity of 32.66 % and similar functional groups to the commercial sample was obtained. These results indicated that the combination of ultrasound with subcritical water is promising to valorize shrimp shell towards production of value-added compounds.

Valorization of black grape pomace by pressurized hot water extraction and hydrolysis: Real-time online and in-line monitoring

The primary aim of this study was to maximize the value of black grape pomace by harnessing innovative and environmentally friendly extraction and hydrolysis technology on the biorefinery concept. This automated system seamlessly integrates pressurized hot water extraction (PHWE) and sequential subcritical water hydrolysis (SubCWH), complemented by inline purification through solid phase extraction (SPE) and online analysis via high-performance liquid chromatography (HPLC) equipped with photodiode array (PDA) and refractive index (RI) detectors. The results of this investigation revealed the presence of twelve anthocyanins, each exceeding a concentration of 3 mgEC3G gDBGP-1. By summing the concentration of these individual anthocyanins, a total yield of 47.6 mgEC3G gDBGP-1 was achieved, attributed to the utilization of acidified water as the solvent and adherence to optimal process conditions. The newly developed system demonstrated its efficacy in both PHWE and SubCWH of black grape pomace, coupled with inline SPE purification and real-time HPLC analysis of various natural compounds. The real-time monitoring capability facilitated swift and efficient responses, reducing processing time, minimizing solvent consumption, decreasing labor requirements, conserving energy, and mitigating environmental impact.

Antioxidant Activity of Egg Yolk Protein Hydrolysates Obtained by Enzymatic and Sub-Critical Water Hydrolysis

Obtaining peptides with antioxidant properties by enzymatic hydrolysis has been widely described; however, the use of non-enzymatic methods to obtain peptides with antioxidant capacities has been poorly investigated. In this study, non-soluble proteins obtained from delipidated egg yolk granules were hydrolyzed with trypsin, and with a non-enzymatic method using sub-critical water hydrolysis under a non-oxidizing (nitrogen) and oxidizing (oxygen) atmosphere. The effect of the sub-critical water hydrolysis on the amino acids’ composition of the hydrolysates was assessed. Furthermore, the antioxidant capacities of the hydrolysates were evaluated using the ABTS•+ scavenging assay, the DPPH radical scavenging activity assay, and by measuring the reducing power of the peptides, the peptides’ ferrous ion chelating capacities, and the antioxidant effect of the peptides on beef homogenates. The hydrolysate obtained by sub-critical water hydrolysis under a nitrogen stream showed similar or better results in the antioxidant tests than those obtained using trypsin hydrolysis, except in the ferrous chelating capacity, where the trypsin hydrolysate showed the best performance. The oxidizing environment promoted by the oxygen in the other sub-critical water hydrolysis method tested produced the peptides with the lowest antioxidant capacities, due to changes in the primary structure of the peptides. These results suggest that the sub-critical water hydrolysis method under a nitrogen stream, in comparison with the enzymatic hydrolysis, is a reliable method to obtain peptides with good antioxidant capacities.

Bio-refinery of brewery spent grain utilizing natural deep eutectic solvent-induced subcritical water

This research aimed to valorize brewery spent grain (BSG) using subcritical water hydrolysis (SWH) modified by six different natural deep eutectic solvents (DES) and determining their bipotentialities. DES-induced SWH BSG hydrolysates showed the highest sugar content 46.63 ± 2.10 mg glucose, protein 228.08 ± 5.52 mg BSA, total flavonoids 22.87 ± 0.23 mg RE, phenolic compounds 8.00 ± 0.25 mg GAE from per gram dried BSG. A total of 9 different essential amino acids were identified from the BSG-hydrolysates; among them, leucine, isoleucine, phenylalanine, and histidine were the most prominent. The major phenolic compounds in the hydrolysates are gallic acid, protocatechuic acid, catechin, 4-hydroxybenzoic acid, naringin, and ferulic acid. BSG hydrolysates demonstrated antimicrobial activities and FT-IR analysis confirmed the presence of bioactive compounds. This comprehensive profiling of different bioactive compounds from BSG using DES-mediated SWH can be helpful for the efficient valorization of BSG for industrial purposes.

Sequential Process of Subcritical Water Hydrolysis and Hydrothermal Liquefaction of Butia Capitata Endocarp to Obtain Fermentable Sugars, Platform Chemicals, Bio-oil, and Biochar.

Butia capitata endocarp (BCE) is a biomass residue with the potential to produce a wide variety of bio-products. The processing of BCE in a sequential process of subcritical water hydrolysis (SWH) and hydrothermal liquefaction (HTL) was investigated to obtain fermentable sugars, platform chemicals, bio-oil, and biochar. The SWH was evaluated at 230 and 260°C and solvent: feed mass ratios (R) of 10 and 20 for the production of fermentable sugars and platform chemicals. The solid residue from SWH was sequentially submitted to the HTL at 330 and 360°C for bio-oil and biochar production. The results were analyzed by comparing the sequential (SWH/HTL) and individual (HTL only) processes. The highest yields of fermentable sugars (5.26g/ 100g BCE) were obtained for SWH at 260°C and R-20 with higher contents of xylose (2.64g/100g BCE) and cellobiose (1.75g/100g BCE). The highest yields of platform chemicals (2.44g/100g BCE) were obtained for SWH at 260°C and R-10 with higher contents of acetic acid (1.78g/100g BCE) and furfural (0.54g/100g BCE). The highest yield of bio-oil (25.30g/100g BCE) occurred in HTL individual process at 360°C and R-20. Sequential process SWH/HTL showed a decrease in bio-oil yield but maintained a similar biochar yield compared to HTL, in addition to the production of fermentable sugars and platform chemicals.

Process optimization and characterization of hydrolysate from underutilized brown macroalgae (Padina tetrastromatica) after fucoidan extraction through subcritical water hydrolysis

The growing demand for macroalgal biomass as a source of proteins, peptides, and amino acids is garnering attention for their biological and functional properties. This study depicts the use of emerging green techniques, i.e. subcritical water, to hydrolyze protein from Padina tetrastromatica. The biomass was treated with subcritical water at varying temperatures between 100 and 220 °C for 10–40 min at a biomass to water proportion of 1:50 (w/v) and pressure of 4.0 MPa. The optimum conditions for recovering the maximum protein (127.2 ± 1.1 mg g−1), free amino acids (58.4 ± 1.0 mg g−1), highest degree of hydrolysis (58.8 ± 1.2 %) and low molecular weight peptides (<650 Da) were found to be 220 °C for 10 min. The amino acid profiling of the hydrolysate revealed that it contains 45 % essential amino acids, with the highest concentration of methionine (0.18 %), isoleucine (0.12 %) and leucine (0.10 %). It was found that the hydrolysate contains phenolics (23.9 ± 1.4 mg GAE g−1) and flavonoids (1.23 ± 0.1 mg QE g−1), which are largely responsible for antioxidant activity. The hydrolysate effectively inhibits acetylcholinesterase and α-amylase in vitro, with IC50 values of 17.9 ± 0.1 mg mL−1 and 16.0 ± 0.5 %, respectively, which can help prevent Alzheimer's disease and diabetes mellitus. Consequently, this study reveals that utilizing eco-friendly subcritical water hydrolysis method, 79 % of the protein was recovered from P. tetrastromatica, which might be an effective source of bioactive peptides in various nutraceutical, pharmaceutical and cosmeceutical applications.

Kinetic and thermodynamic study of pyrolysis of the hydrolyzed residue of rice straw and husk by subcritical water process using thermogravimetric analysis

AbstractThe use of hydrolyzed rice straw (HRS) and hydrolyzed rice husk (HRH) as feedstock for pyrolysis was evaluated through kinetic and thermodynamic studies. HRS and HRH were obtained from subcritical water hydrolysis (SWH) at different temperatures (180, 220, and 260°C). The Coats‐Redfern method was used to analyze the thermal behavior through thermogravimetry (TG) and derivative thermogravimetry (DTG) curves. TG profiles showed higher decomposition in the range of 250–400°C, especially for rice straw (RS) and HRS (80 wt %). The pyrolysis curves were well predicted by a first‐order reaction model. The kinetic analysis showed a variation in activation energy (EA) between 24.3 to 41.3 kJ mol−1 and 40.4 to 54.7 kJ mol−1 for RS/HRS and rice husk (RH)/HRH, respectively. The enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) varied from 25.9 to 39.6 kJ mol−1, 35.4 to 69.6 kJ mol−1, and −64.1 to −6.7 J mol−1 K−1, respectively, for RS/HRS, and 35 to 49.8 kJ mol−1, 43.2 to 79.3 kJ mol−1, and −53.5 to −10.2 J mol−1 K−1, respectively, for RH/HRH. These results showed that the pyrolysis reactivity using HRS is higher than HRH, which indicates the pyrolysis of HRS is more advantageous than HRH.

Obtaining oil, fermentable sugars, and platform chemicals from Butia odorata seed using supercritical fluid extraction and subcritical water hydrolysis

Butia odorata seeds (BOS) present high economical potential because they contain oil and lignocellulosic compounds. Oil extracted by supercritical technology may have potential use in the food industry and the remaining solid from the process can be used to produce second- generation ethanol from the hydrolysis of its carbohydrates to obtain fermentable sugars. This work evaluates the processing of BOS using supercritical fluid extraction (SFE), to obtain oil, and subsequent subcritical water hydrolysis (SWH) of SFE residue (BOSR), to obtain fermentable sugars and platform chemicals. Kinetic curves at temperatures of 40 °C and 60 °C, and pressures of 18, 20, and 22 MPa were obtained for SFE using CO2 as solvent, with the best oil yield of 29.05 ± 1.42 wt% at 60 °C and 22 MPa. In the SWH, the explored conditions were 230 °C and 260 °C for temperature, 50 and 100 for solvent to feed ratio (S/F) with a constant pressure of 15 MPa. The best results for the yields of fermentable sugars and platform chemicals were 5.78 ± 1.15 g/100 g and 2.90 ± 0.24 g/100 g, respectively, at 260 °C and S/F 50.

Biogas production from food waste hydrolysate using a subcritical water pretreated process and pulp wastewater seed sludge

This study was investigated the biogas production performance from subcritical water hydrolysate (SCWH) using a pretreated food waste (FW) process, and pulp wastewater (PW) as seed sludge according to different volatile solid (VS) ratio of PW to SCWH, and different substrate concentration. The subcritical water hydrolysis was acted for 30 mins in a 70 ml Teflon reactor under different temperatures varied from 119, 129, 139, 159, and 195 ℃, respectively. A batch system for optimal biogas and methane production yields examination were fermented in a 60 ml flask under 37 °C and 120 rpm. A maximum biogas yield of 807.0 ml/g VSre and methane yield of 329.5 ml/g VSre were achieved at a VS ratio of PW to SCWH 1:3 and substrate concentration of 25 g/L with a hydrolysate under 159 ℃ and the volatile solids (VS) removal efficiency of 80%. These results indicated that the food waste pretreated by subcritical water hydrolysis can efficiently increase the biogas production under optimal conditions.

Valorization of Kappaphycus alvarezii through extraction of high-value compounds employing green approaches and assessment of the therapeutic potential of κ-carrageenan

This study utilizes different emerging green extraction technologies to recover maximum value-added products from Kappaphycus alvarezii and evaluate their bio-functional properties. Using the supercritical fluid extraction (SFE) method, the total lipid yield of 0.21 ± 0.2 % was obtained from the biomass. Linoleic acid, eicosapentaenoic acid, arachidonic acid, γ-linolenic acid, and docosahexaenoic acid were present in higher concentrations (9.12 %) in the lipid extracted with SFE as compared to hexane (5.5 %). Using an ultrasonication assisted approach, ~56 % of κ-carrageenan was recovered from SFE residual biomass, which contains 28.5 ± 1.9 % sulfate content. It exhibited a monosaccharide content of 3,6-anhydrogalactose (~24 %) and galactose (~53 %), as well as rheological properties within FAO limitations that can be explored for food-grade applications. ~58 % of the total protein (12.5 %) from SFE residual biomass was recovered using subcritical water hydrolysis method. The effectiveness of κ-carrageenan in suppressing the 3CLpro of SARS-CoV-2 using in vitro and in silico approaches was investigated. κ-Carrageenan effectively inhibited the main protease by up to 93 % at 1.6 mg mL−1. In silico results revealed that κ-carrageenan successfully binds to the active site of the main protease while retaining the structural integrity and stability of protein-ligand complexes.