Marine enzymes: Classification and application in various industries

Last Decade Insights in Exploiting Marine Microorganisms as Sources of New Bioactive Natural Products

Marine microorganisms have emerged as prolific sources of bioactive natural products, offering a large chemical diversity and a broad spectrum of biological activities. Over the past decade, significant progress has been made in discovering and characterizing these compounds, pushed by technological innovations in genomics, metabolomics, and bioinformatics. Furthermore, innovative isolation and cultivation approaches have improved the isolation of rare and difficult-to-culture marine microbes, leading to the identification of novel secondary metabolites. Advances in synthetic biology and metabolic engineering have further optimized natural product yields and the generation of novel compounds with improved bioactive properties. This review highlights key developments in the exploitation of marine bacteria, fungi, and microalgae for the discovery of novel natural products with potential applications in diverse fields, underscoring the immense potential of marine microorganisms in the growing Blue Economy sector.

Purification, characterization, structural elucidation, and industrial applications of thermostable alkaline protease produced by seaweed-associated Nocardiopsis dassonvillei strain VCs-4

Alkaline proteases are crucial in the enzyme industry. The seaweed-associated strain Nocardiopsis dassonvillei strain VCs-4 produced a protease with the optimal activity of 362.97 U/mL under haloalkaliphilic conditions. Kinetic analysis revealed a Km of 0.17 mg/mL, Vmax of 1928 U/mL/min, and Kcat of 16.66 s-1. The VCs-4 protease showed remarkable stability against chemical stresses, including surfactants, detergents, and bleaching agents, making it suitable for industrial use. Its thermal stability was demonstrated with a ΔH* of 73.36 kJ/mol, ΔS* of -87.27 J/mol, and a half-life (t₁/₂) of 15 min at 80 °C, extended to 19 min in 2 M NaCl. Structural analysis using FTIR and CD spectroscopy revealed a predominance of α-helices (79.64 %) and minimal β-strands (0.55 %) at 60 °C. Additionally, 97.78 % of the residues were in the most preferred regions of the Ramachandran plot, reflecting high stereochemical quality. The enzyme composition includes 17 % cysteine and 8.5 % serine residues, with a charge profile of four negatively charged (Asp, Glu) and seven positively charged (Arg, Lys) residues. The VCs-4 protease demonstrated potential for industrial applications, successfully removing blood stains and hydrolyzing gelatin from used X-ray film.

Agro-industrial Waste Utilization, Medium Optimization, and Immobilization of Economically Feasible Halo-Alkaline Protease Produced by Nocardiopsis dassonvillei Strain VCS-4

The oceanic actinobacteria have strong potential to secrete novel enzymes with unique properties useful for biotechnological applications. The Nocardiopsis dassonvillei strain VCS-4, associated with seaweed Caulerpa scalpeliformis, was a halo-alkaline protease producer. Further investigation focuses on medium optimization and the use of agro-industrial waste for economically feasible, high-yield protease production. A total of 12 experimental runs were designed using Minitab-20 software and Placket-Burman design. Among the 7 physicochemical parameters analyzed, incubation time and gelatin were detected as significant factors responsible for higher protease production. Incubation time and gelatin were further analyzed using OVATs. Optimal protease production was achieved with 2% gelatin, 0.1% yeast extract, 0.1% bacteriological peptone, 7% NaCl, pH 8, 5% inoculum, and a 7-day incubation period, resulting in a maximum protease activity (Pmax) of 363.97 U/mL, generation time of 11.9 h, specific growth rate of 0.161 g/mL/h, and protease productivity (Qp) of 61.65 U/mL/h. Moreover, utilizing groundnut cake as an agro-industrial waste led to enhanced production parameters: Pmax of 408.42 U/mL, generation time of 9.74 h, specific growth rate of 0.361 g/mL/h, and Qp of 68.07 U/mL/h. The immobilization of crude protease was achieved using Seralite SRC 120 as a support matrix resulting in 470.38 U/g immobilization, 88.20% immobilization yield, and 28.90% recovery activity. Characterization of both crude and immobilized proteases revealed optimal activity at pH 10 and 70 °C. Immobilization enhanced the shelf-life, reusability, and stability of VCS-4 protease under extreme conditions.

Marine chitinase AfChi: green defense management against Colletotrichum gloeosporioides and anthracnose

Anthracnose disease, caused by the Colletotrichum gloeosporioides species, affects vegetables, fruits, pulses, and cereals, leading to significant economic losses worldwide. Although many synthetic fungicides are used to control this pathogen, eco-friendly biological alternatives are gaining popularity. This study focuses on isolating and purifying chitinase ( Af Chi)from a marine bacterium and testing its antifungal efficacy against C. gloeosporioides spore germination by targeting the chitin in the fungal cell wall. The chitinase was purified from a marine bacterium A. faecalis from the Arabian Sea and had a molecular mass of 45 kDa and a specific activity of 84.6 U/mg. Af Chi worked best at 50 °C and pH 7.0 in Tris HCl buffer. Na+ ion was the highest cofactor, highlighting the halophilic nature of this chitinase. K+, Ca2+, Cu2+, Mg2+, Mn2+, and EDTA also increased activity, while Fe3+, Zn2+, Co2+, and Pb2+ decreased it. The Km and Vmax values were 1.87 µg/mL and 17.45 U/mL, respectively. Purified Af Chi at 10 mg/mL completely inhibited spore germination within 8 h and reduced the size of the spores.

Investigating the nutritional viability of marine-derived protein for sustainable future development

Marine-derived proteins are emerging as a pivotal resource with diverse applications in food, pharmaceuticals, and biotechnological industries. The marine environment offers many protein sources, including fish, shellfish, algae, and microbes, which garnered attention due to their nutritional composition. Evaluating their protein and amino acid profiles is essential in assessing their viability as substitutes for conventional protein sources. Continuously exploiting marine ecosystems for protein extraction has led to significant environmental impacts. The optimization of aquacultural practices and implementation of innovative practices are imperative for the sustainable production of marine-based protein. This review will discuss the different sources of marine proteins, their nutritional profile, and their associated environmental impact. It also reviews the relationship between aquaculture advancements and regulatory frameworks toward attaining sustainable practices, alongside exploring the challenges and potentials in utilizing marine sources for protein production.

Marine-Derived Lipases for Enhancing Enrichment of Very-Long-Chain Polyunsaturated Fatty Acids with Reference to Omega-3 Fatty Acids

Omega-3 fatty acids are essential fatty acids that are not synthesised by the human body and have been linked with the prevention of chronic illnesses such as cardiovascular and neurodegenerative diseases. However, the current dietary habits of the majority of the population include lower omega-3 content compared to omega-6, which does not promote good health. To overcome this, pharmaceutical and nutraceutical companies aim to produce omega-3-fortified foods. For this purpose, various approaches have been employed to obtain omega-3 concentrates from sources such as fish and algal oil with higher amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Among these techniques, enzymatic enrichment using lipase enzymes has gained tremendous interest as it is low in capital cost and simple in operation. Microorganism-derived lipases are preferred as they are easily produced due to their higher growth rate, and they hold the ability to be manipulated using genetic modification. This review aims to highlight the recent studies that have been carried out using marine lipases for the enrichment of omega-3, to provide insight into future directions. Overall, the covalent bond-based lipase immobilization to various support materials appears most promising; however, greener and less expensive options need to be strengthened.

Improved production of alkaline and solvent-stable proteases from a halotolerant Exiguobacterium isolate through heterologous expression

Halophiles are excellent sources of detergent proteases that are attributed to stability in alkaline pH, salts, surfactants, and hydrophobic solvents. The lower enzymatic yields and tedious downstream processes necessitate the search for newer halophilic sources. We have previously reported a halotolerant Exiguobacterium sp. TBG-PICH-001, which secretes solvent-tolerant alkaline protease/s. The present study describes the heterologous expression of two protease genes, namely, rsep metalloprotease (WP_195864791, 1.23 Kb) and tpa serine protease (WP_195864453, 0.879 Kb) genes. These were cloned into the pET 22b + plasmid vector and expressed in Escherichia coli BL21(DE3). The recombinant proteases rsep and tpa showed respective yields of 6.3 and 6.7 IU/mg, 11 and 12-fold higher than the crude native protease/s from TBG-PICH-001. These showed soluble expression at 46 and 32 KDa, respectively. These were purified to homogeneity through Ni-NTA-affinity chromatography. The purified proteases were characterized for properties like pH & temperature optima and stability, substrate specificity, kinetic parameters, and detergent attributes. They showed affinity towards various substrates with a respective Km of 392 and 301 μM towards casein. The recombinant proteases exhibited stability in the alkaline pH (7-10), surfactants, metal ions, detergents, and hydrophobic solvents, rendering their suitability as detergent additives.

Marine-derived Compounds: A Powerful Platform for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a debilitating form of dementia that primarily affects cholinergic neurons in the brain, significantly reducing an individual's capacity for learning and creative skills and ultimately resulting in an inability to carry out even basic daily tasks. As the elderly population is exponentially increasing, the disease has become a significant concern for society. Therefore, neuroprotective substances have garnered considerable interest in addressing this universal issue. Studies have shown that oxidative damage to neurons contributes to the pathophysiological processes underlying AD progression. In AD, tau phosphorylation and glutamate excitotoxicity may play essential roles, but no permanent cure for AD is available. The existing therapies only manage the early symptoms of AD and often come with numerous side effects and toxicities. To address these challenges, researchers have turned to nature and explored various sources such as plants, animals, and marine organisms. Many historic holy books from different cultures emphasize that adding marine compounds to the regular diet enhances brain function and mitigates its decline. Consequently, researchers have devoted significant time to identifying potentially active neuroprotective substances from marine sources. Marine-derived compounds are gaining recognition due to their abundant supply of diverse chemical compounds with biological and pharmacological potential and unique mechanisms of action. Several studies have reported that plants exhibit multitarget potential in treating AD. In light of this, the current study focuses on marine-derived components with excellent potential for treating this neurodegenerative disease.

Non-deteriorative eco-friendly water-saving tactic for removal of vegetable matters from wool fleece using xylanase and cellulase

The carbonization of wool fleece (WF) is conducted to remove the adhered vegetable matter (VM) from contaminated WF using sulfuric acid, followed by drying and backing. This process has a deteriorative effect on WF and requires a tremendous quantity of water for rinsing WF after carbonization to remove any H2SO4 residuals. Herein, we propose an alternative eco-friendly water-saving process for the removal of VM from WF using enzymes. Cellulase-containing xylanase from the fungus Aspergillus terreus, and cellulase-free xylanase from the fungus Aspergillus flavus AW1 were used to remove the VM from WF. The effect of some process parameters on the amount of the removed VM was assessed. Alkali solubility as well as sulfur and cystine content were used to follow the alteration in the chemistry of the bio-treated WF. The fiber morphology was examined using scanning electron microscopy. The dyeability of the treated WF towards acid, reactive, and basic dyes was monitored. The results revealed that the removal of the VM from WF by applying the examined enzymes was effective and could be an appropriate, non-destructive, eco-friendly water-saving substitute to the conventional carbonization procedures. By virtue of enzyme specificity, the proposed process removed the VM without deteriorating the fiber.

High-Value Utilization of Marine Biological Resources

The ocean covers 71% of the surface of our planet and comprises a diverse variety of biological resources-a combination of marine animals, marine plants, and marine microorganisms that have economic value for human beings [...].

A novel salt- and organic solvent-tolerant phosphite dehydrogenase from Cyanothece sp. ATCC 51142

Phosphite dehydrogenase (PtxD) is a promising enzyme for NAD(P)H regeneration. To expand the usability of PtxD, we cloned, expressed, and analyzed PtxD from the marine cyanobacterium Cyanothece sp. ATCC 51142 (Ct-PtxD). Ct-PtxD exhibited maximum activity at pH 9.0°C and 50°C and high stability over a wide pH range of 6.0-10.0. Compared to previously reported PtxDs, Ct-PtxD showed increased resistance to salt ions such as Na+, K+, and NH4 +. It also exhibited high tolerance to organic solvents such as ethanol, dimethylformamide, and methanol when bound to its preferred cofactor, NAD+. Remarkably, these organic solvents enhanced the Ct-PtxD activity while inhibiting the PtxD activity of Ralstonia sp. 4506 (Rs-PtxD) at concentrations ranging from 10% to 30%. Molecular electrostatic potential analysis showed that the NAD+-binding site of Ct-PtxD was rich in positively charged residues, which may attract the negatively charged pyrophosphate group of NAD+ under high-salt conditions. Amino acid composition analysis revealed that Ct-PtxD contained fewer hydrophobic amino acids than other PtxD enzymes, which reduced the hydrophobicity and increased the hydration of protein surface under low water activity. We also demonstrated that the NADH regeneration system using Ct-PtxD is useful for the coupled chiral conversion of trimethylpyruvic acid into L-tert-leucine using leucine dehydrogenase under high ammonium conditions, which is less supported by the Rs-PtxD enzyme. These results imply that Ct-PtxD might be a potential candidate for NAD(P)H regeneration in industrial applications under the reaction conditions containing salt and organic solvent.

A review on the emerging conversion technology of cellulose, starch, lignin, protein and other organics from vegetable-fruit-based waste

A large amount of vegetable-fruit-based waste (VFBW) belonging to agricultural waste is produced around the world every year, imposing a huge burden on the environment and sustainable development. VFBW contains a lot of water and useful organic compounds (e.g., cellulose, minerals, starch, proteins, organic acids, lipids, and soluble sugars). Taking into account the composition characteristics and circular economy of VFBW, many new emerging conversion technologies for the treatment of VFBW (such as hydrothermal gasification, ultrasound-assisted extraction, and synthesis of bioplastics) have been developed. This review summarizes the current literature discussing the technical parameters, process, mechanism, and characteristics of various emerging conversion methods, as well as analyzing the application, environmental impact, and bio-economy of by-products from the conversion process, to facilitate solutions to the key problems of engineering cases using these methods. The shortcomings of the current study and the direction of future research are also highlighted in the review.

Hydrothermal Processing of Agar Waste to Levulinic acid and Fermentation of Hydrolysate to Bioethanol

Increasing global energy consumption and depleting fossil-fuel supplies prompted the search for green-alternatives. This study focuses on conversion of waste agar using different acids/alkalis (0.5% and 1%) as catalysts under varied temperature and time towards galactose (Gal), 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) production in a sequential reaction. The optimized process for agar depolymerisation was achieved using 1 % acid (H₂SO₄/HCl) catalysed conditions with a maximum of 11 g/L Gal yield (121 °C; 15 min). Increase in temperature (150 °C) and time (180 min) with 1% HCl/H₂SO₄ catalyst resulted in improved LA production along with Gal and HMF. The hydrolysis process was optimised for the selective production of LA (10 g/L) at 175 °C; 180 min. Further, galactose-rich hydrolysates were assessed for bioethanol fermentation using Saccharomyces cerevisiae and resulted 3 g/L ethanol. Thus, the study comprehensively demonstrates waste agar utilization to yield biochemicals/fuels in a circular bio-based economy approach.