Marine enzymes: Classification and application in various industries

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.

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.

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.