An overview on marine cellulolytic enzymes and their potential applications

Blue Biotechnology: Marine Bacteria Bioproducts

The ocean is the habitat of a great number of organisms with different characteristics. Compared to terrestrial microorganisms, marine microorganisms also represent a vast and largely unexplored reservoir of bioactive compounds with diverse industrial applications like terrestrial microorganisms. This review examines the properties and potential applications of products derived from marine microorganisms, including bacteriocins, enzymes, exopolysaccharides, and pigments, juxtaposing them in some cases against their terrestrial counterparts. We discuss the distinct characteristics that set marine-derived products apart, including enhanced stability and unique structural features such as the amount of uronic acid and sulfate groups in exopolysaccharides. Further, we explore the uses of these marine-derived compounds across various industries, ranging from food and pharmaceuticals to cosmetics and biotechnology. This review also presents a broad description of biotechnologically important compounds produced by bacteria isolated from marine environments, some of them with different qualities compared to their terrestrial counterparts.

Purification and Properties of a Plasmin-like Marine Protease from Clamworm (Perinereis aibuhitensis)

Marine organisms are a rich source of enzymes that exhibit excellent biological activity and a wide range of applications. However, there has been limited research on the proteases found in marine mudflat organisms. Based on this background, the marine fibrinolytic enzyme FELP, which was isolated and purified from clamworm (Perinereis aibuhitensis), has exhibited excellent fibrinolytic activity. We demonstrated the FELP with a purification of 10.61-fold by precipitation with ammonium sulfate, ion-exchange chromatography, and gel-filtration chromatography. SDS-PAGE, fibrin plate method, and LC-MS/MS indicated that the molecular weight of FELP is 28.9 kDa and identified FELP as a fibrinolytic enzyme-like protease. FELP displayed the maximum fibrinolytic activity at pH 9 (407 ± 16 mm2) and 50 °C (724 ± 27 mm2) and had excellent stability at pH 7-11 (50%) or 30-60 °C (60%), respectively. The three-dimensional structure of some amino acid residues of FELP was predicted with the SWISS-MODEL. The fibrinolytic and fibrinogenolytic assays showed that the enzyme possessed direct fibrinolytic activity and indirect fibrinolysis via the activation of plasminogen; it could preferentially degrade Aα-chains of fibrinogen, followed by Bβ- and γ-chains. Overall, the fibrinolytic enzyme was successfully purified from Perinereis aibuhitensis, a marine Annelida (phylum), with favorable stability that has strong fibrinolysis activity in vitro. Therefore, FELP appears to be a potent fibrinolytic enzyme with an application that deserves further investigation.

Study of marine microorganism metabolites: new resources for bioactive natural products

The marine environment has remained a source of novel biological molecules with diversified applications. The ecological and biological diversity, along with a unique physical environment, have provided the evolutionary advantage to the plant, animals and microbial species thriving in the marine ecosystem. In light of the fact that marine microorganisms frequently interact symbiotically or mutualistically with higher species including corals, fish, sponges, and algae, this paper intends to examine the potential of marine microorganisms as a niche for marine bacteria. This review aims to analyze and summarize modern literature data on the biotechnological potential of marine fungi and bacteria as producers of a wide range of practically valuable products (surfactants, glyco-and lipopeptides, exopolysaccharides, enzymes, and metabolites with different biological activities: antimicrobial, antitumor, and cytotoxic). Hence, the study on bioactive secondary metabolites from marine microorganisms is the need of the hour. The scientific novelty of the study lies in the fact that for the first time, the data on new resources for obtaining biologically active natural products - metabolites of marine bacteria and fungi - were generalized. The review investigates the various kinds of natural products derived from marine microorganisms, specifically focusing on marine bacteria and fungi as a valuable source for new natural products. It provides a summary of the data regarding the antibacterial, antimalarial, anticarcinogenic, antibiofilm, and anti-inflammatory effects demonstrated by marine microorganisms. There is currently a great need for scientific and applied research on bioactive secondary metabolites of marine microorganisms from the standpoint of human and animal health.

Systematic bioprospection for cellulolytic actinomycetes in the Chihuahuan Desert: isolation and enzymatic profiling

The quest for microbial cellulases has intensified as a response to global challenges in biofuel production. The efficient deconstruction of lignocellulosic biomass holds promise for generating valuable products in various industries such as food, textile, and detergents. This article presents a systematic bioprospection aimed at isolating actinomycetes with exceptional cellulose deconstruction capabilities. Our methodology explored the biodiverse oligotrophic region of Cuatro Cienegas, Coahuila, within the Chihuahuan Desert. Among the evaluated actinomycetes collection, 78% exhibited cellulolytic activity. Through a meticulous screening process based on enzymatic index evaluation, we identified a highly cellulolytic Streptomyces strain for further investigation. Submerged fermentation of this strain revealed an endoglucanase enzymatic activity of 149 U/mg. Genomic analysis of strain Streptomyces sp. STCH565-A revealed unique configurations of carbohydrate-active enzyme (CAZyme) genes, underscoring its potential for lignocellulosic bioconversion applications. These findings not only highlight the significance of the Chihuahuan Desert as a rich source of cellulolytic microorganisms but also offer insights into the systematic exploration and selection of high-performing cellulolytic microorganisms for application in diverse environmental contexts. In conclusion, our bioprospecting study lays a foundation for harnessing the cellulolytic potential of actinomycetes from the Chihuahuan Desert, with implications for advancing cellulose deconstruction processes in various industries. The findings can serve as a blueprint for future bioprospecting efforts in different regions, facilitating the targeted discovery of microorganisms with exceptional cellulosic deconstruction capabilities.

Quantification of Xylanolytic and Cellulolytic Activities of Fungal Strains Isolated from Palmaria palmata to Enhance R-Phycoerythrin Extraction of Palmaria palmata: From Seaweed to Seaweed

R-phycoerythrin (R-PE) can be enzymatically extracted from red seaweeds such as Palmaria palmata. This pigment has numerous applications and is notably known as an antioxidant, antitumoral or anti-inflammatory agent. Enzymes secreted by P. palmata associated fungal strains were assumed to be efficient and adapted for R-PE extraction from this macroalga. The aim of the present study was to quantify both xylanolytic and cellulolytic activities of enzymatic extracts obtained from six Palmaria palmata derived fungal strains. Degradation of P. palmata biomass by fungal enzymatic extracts was also investigated, focused on soluble protein and R-PE extraction. Enzymatic extracts were obtained by solid state fermentation. Macroalgal degradation abilities were evaluated by measuring reducing sugar release using DNS assays. Soluble proteins and R-PE recovery yields were evaluated through bicinchoninic acid and spectrophotometric assays, respectively. Various enzymatic activities were obtained according to fungal isolates up to 978 U/mL for xylanase and 50 U/mL for cellulase. Enzymatic extract allowed high degrading abilities, with four of the six fungal strains assessed exhibiting at least equal results as the commercial enzymes for the reducing sugar release. Similarly, all six strains allowed the same soluble protein extraction yield and four of them led to an improvement of R-PE extraction. R-PE extraction from P. palamata using marine fungal enzymes appeared particularly promising. To the best of our knowledge, this study is the first on the use of enzymes of P. palmata associated fungi in the degradation of its own biomass for biomolecules recovery.

Comparative Genomic Analyses of Cellulolytic Machinery Reveal Two Nutritional Strategies of Marine Labyrinthulomycetes Protists

Labyrinthulomycetes are a group of ubiquitous and diverse unicellular Stramenopiles and have long been known for their vital role in ocean carbon cycling. However, their ecological function from the perspective of organic matter degradation remains poorly understood. This study reports high-quality genomes of two newly isolated Labyrinthulomycetes strains, namely, Botryochytrium sp. strain S-28 and Oblongichytrium sp. strain S-429, and provides molecular analysis of their ecological functions using comparative genomics and a biochemical assay. Our results suggest that Labyrinthulomycetes may occupy multiple ecological niches in marine ecosystems because of the significant differences in gene function among different genera. Certain strains could degrade wheat bran independently by secreting cellulase. The key glycoside hydrolase families (GH1, GH5, and GH9) related to cellulase and the functional domains of carbohydrate-active enzymes (CAZymes) were more enriched in their genomes. This group can actively participate in marine biochemical cycles as decomposers. In contrast, other strains that could not produce cellulase may thrive as "leftover scavengers" and act as a source of nutrients to the higher-trophic-level plankton. In addition, our findings emphasize the dual roles of endoglucanase, acting as both exo- and endoglucanases, in the process of cellulose degradation. Using genomic, biochemical, and phylogenetic analyses, our study provides a broader insight into the nutritional patterns and ecological functions of Labyrinthulomycetes. IMPORTANCE Unicellular heterotrophic eukaryotes are an important component of marine ecosystems. However, their ecological functions and modes of nutrition remain largely unknown. Our current understanding of marine microbial ecology is incomplete without integrating these heterotrophic microeukaryotes into the food web models. This study focuses on the unicellular fungus-like protists Labyrinthulomycetes and provides two high-quality genomes of cellulase-producing Labyrinthulomycetes. Our study uncovers the basis of their cellulase production by deciphering the results of genomic, biochemical, and phylogenetic analyses. This study instigates a further investigation of the molecular mechanism of organic matter utilization by Labyrinthulomycetes in the world's oceans.

Lignocellulolytic Biocatalysts: The Main Players Involved in Multiple Biotechnological Processes for Biomass Valorization

Human population growth, industrialization, and globalization have caused several pressures on the planet's natural resources, culminating in the severe climate and environmental crisis which we are facing. Aiming to remedy and mitigate the impact of human activities on the environment, the use of lignocellulolytic enzymes for biofuel production, food, bioremediation, and other various industries, is presented as a more sustainable alternative. These enzymes are characterized as a group of enzymes capable of breaking down lignocellulosic biomass into its different monomer units, making it accessible for bioconversion into various products and applications in the most diverse industries. Among all the organisms that produce lignocellulolytic enzymes, microorganisms are seen as the primary sources for obtaining them. Therefore, this review proposes to discuss the fundamental aspects of the enzymes forming lignocellulolytic systems and the main microorganisms used to obtain them. In addition, different possible industrial applications for these enzymes will be discussed, as well as information about their production modes and considerations about recent advances and future perspectives in research in pursuit of expanding lignocellulolytic enzyme uses at an industrial scale.

A comprehensive review on strategic study of cellulase producing marine actinobacteria for biofuel applications

Every year, 180 billion tonnes of cellulose are produced by plants as waste biomass after the cultivation of the desired product. One of the smart and effective ways to utilize this biomass rather than burn it is to utilize the biomass to adequately meet the energy needs with the help of microbial cellulase that can catalytically convert the cellulose into simple sugar units. Marine actinobacteria is one of the plentiful gram-positive bacteria known for its industrial application as it can produce multienzyme cellulase with high thermal tolerance, pH stability and high resistant towards metal ions and salt concentration, along with other antimicrobial properties. Highly stable cellulase obtained from marine actinobacteria will convert the cellulose biomass into glucose, which is the precursor for biofuel production. This review will provide a comprehensive outlook of various strategic applications of cellulase from marine actinobacteria which can facilitate the breakdown of lignocellulosic biomass to bioenergy with respect to its characteristics based on the location/environment that the organism was collected and its screening strategies followed by adopted methodologies to mine the novel cellulase genome and enhance the production, thereby increasing the activity of cellulase continued by effective immobilization on novel substrates for the multiple usage of cellulase along with the industrial applications.

Marine Bacterial Dextranases: Fundamentals and Applications

Dextran, a renewable hydrophilic polysaccharide, is nontoxic, highly stable but intrinsically biodegradable. The α-1, 6 glycosidic bonds in dextran are attacked by dextranase (E.C. 3.2.1.11) which is an inducible enzyme. Dextranase finds many applications such as, in sugar industry, in the production of human plasma substitutes, and for the treatment and prevention of dental plaque. Currently, dextranases are obtained from terrestrial fungi which have longer duration for production but not very tolerant to environmental conditions and have safety concerns. Marine bacteria have been proposed as an alternative source of these enzymes and can provide prospects to overcome these issues. Indeed, marine bacterial dextranases are reportedly more effective and suitable for dental caries prevention and treatment. Here, we focused on properties of dextran, properties of dextran—hydrolyzing enzymes, particularly from marine sources and the biochemical features of these enzymes. Lastly the potential use of these marine bacterial dextranase to remove dental plaque has been discussed. The review covers dextranase-producing bacteria isolated from shrimp, fish, algae, sea slit, and sea water, as well as from macro- and micro fungi and other microorganisms. It is common knowledge that dextranase is used in the sugar industry; produced as a result of hydrolysis by dextranase and have prebiotic properties which influence the consistency and texture of food products. In medicine, dextranases are used to make blood substitutes. In addition, dextranase is used to produce low molecular weight dextran and cytotoxic dextran. Furthermore, dextranase is used to enhance antibiotic activity in endocarditis. It has been established that dextranase from marine bacteria is the most preferable for removing plaque, as it has a high enzymatic activity. This study lays the groundwork for the future design and development of different oral care products, based on enzymes derived from marine bacteria.

Homoscleromorpha-derived Bacillus spp. as potential sources of biotechnologically-relevant hydrolases and biosurfactants

Despite hydrolytic exoenzymes and biosurfactants having been gradually reported from the poriferan microbiome, little is known about these bioproducts in microorganisms inhabiting Homoscleromorpha sponges. Here, we investigated the production of hydrolases and biosurfactants in bacteria isolated from three shallow-water homoscleromorph species, Oscarella sp., Plakina cyanorosea, and Plakina cabofriense. A total of 99 of 107 sponge-associated bacterial isolates exhibited activity for at least one of the analyzed hydrolases. Following fermentation in Luria-Bertani (LB) and Tryptic Soy Broth (TSB), two isolates, 80BH11 and 80B1:1010b, showed higher lipase and peptidase activities. Both of them belonged to the Bacillus genus and were isolated from Oscarella. Central composite design leveraged up the peptidase activity in 280% by Bacillus sp. 80BH11 in the TSB medium for 48 h at 30 °C. The optimized model also revealed that pH 6.5 and 45 °C were the best conditions for peptidase reaction. In addition, Bacillus sp. 80BH11 was able to release highly emulsifying and remarkably stable surfactants in the LB medium. Surfactin was finally elucidated as the biosurfactant generated by this sponge-derived Bacillus. In conclusion, we hope to have set the scenery for further prospecting of industrial enzymes and biosurfactants in Homoscleromorpha microbiomes.

Cellulolytic and Xylanolytic Enzymes from Yeasts: Properties and Industrial Applications

Lignocellulose, the main component of plant cell walls, comprises polyaromatic lignin and fermentable materials, cellulose and hemicellulose. It is a plentiful and renewable feedstock for chemicals and energy. It can serve as a raw material for the production of various value-added products, including cellulase and xylanase. Cellulase is essentially required in lignocellulose-based biorefineries and is applied in many commercial processes. Likewise, xylanases are industrially important enzymes applied in papermaking and in the manufacture of prebiotics and pharmaceuticals. Owing to the widespread application of these enzymes, many prokaryotes and eukaryotes have been exploited to produce cellulase and xylanases in good yields, yet yeasts have rarely been explored for their plant-cell-wall-degrading activities. This review is focused on summarizing reports about cellulolytic and xylanolytic yeasts, their properties, and their biotechnological applications.

Alginate Lyases from Marine Bacteria: An Enzyme Ocean for Sustainable Future

The cell wall of brown algae contains alginate as a major constituent. This anionic polymer is a composite of β-d-mannuronate (M) and α-l-guluronate (G). Alginate can be degraded into oligosaccharides; both the polymer and its products exhibit antioxidative, antimicrobial, and immunomodulatory activities and, hence, find many commercial applications. Alginate is attacked by various enzymes, collectively termed alginate lyases, that degrade glycosidic bonds through β-elimination. Considering the abundance of brown algae in marine ecosystems, alginate is an important source of nutrients for marine organisms, and therefore, alginate lyases play a significant role in marine carbon recycling. Various marine microorganisms, particularly those that thrive in association with brown algae, have been reported as producers of alginate lyases. Conceivably, the marine-derived alginate lyases demonstrate salt tolerance, and many are activated in the presence of salts and, therefore, find applications in the food industry. Therefore, this review summarizes the structural and biochemical features of marine bacterial alginate lyases along with their applications. This comprehensive information can aid in the expansion of future prospects of alginate lyases.

Genome Analysis of Celeribacter sp. PS-C1 Isolated from Sekinchan Beach in Selangor, Malaysia, Reveals Its β-Glucosidase and Licheninase Activities

A halophilic marine bacterial strain, PS-C1, was isolated from Sekinchan beach in Selangor, Malaysia. The 16S rRNA gene sequence analysis indicated that strain PS-C1 was associated with the genus Celeribacter. To date, there have been no reports on enzymes from the genus Celeribacter. The present study reports on the cellular features of Celeribacter sp. PS-C1, its annotated genome sequence, and comparative genome analyses of Celeribacter glycoside hydrolase (GH) enzymes. The genome of strain PS-C1 has a size of 3.87 Mbp and a G+C content of 59.10%, and contains 3739 protein-coding genes. Detailed analysis using the Carbohydrate-Active enZYmes (CAZy) database revealed that Celeribacter genomes harboured at least 12 putative genes encoding industrially important GHs that are grouped as cellulases, β-glucanases, hemicellulases, and starch-degrading enzymes. Herein, the potential applications of these enzymes are discussed. Furthermore, the activities of two types of GHs (β-glucosidase and licheninase) in strain PS-C1 were demonstrated. These findings suggest that strain PS-C1 could be a reservoir of novel GH enzymes for lignocellulosic biomass degradation.

Marine Microbial Fibrinolytic Enzymes: An Overview of Source, Production, Biochemical Properties and Thrombolytic Activity

Cardiovascular diseases (CVDs) have emerged as a major threat to global health resulting in a decrease in life expectancy with respect to humans. Thrombosis is one of the foremost causes of CVDs, and it is characterized by the unwanted formation of fibrin clots. Recently, microbial fibrinolytic enzymes due to their specific features have gained much more attention than conventional thrombolytic agents for the treatment of thrombosis. Marine microorganisms including bacteria and microalgae have the significant ability to produce fibrinolytic enzymes with improved pharmacological properties and lesser side effects and, hence, are considered as prospective candidates for large scale production of these enzymes. There are no studies that have evaluated the fibrinolytic potential of marine fungal-derived enzymes. The current review presents an outline regarding isolation sources, production, features, and thrombolytic potential of fibrinolytic biocatalysts from marine microorganisms identified so far.

Mangrove crab intestine and habitat sediment microbiomes cooperatively work on carbon and nitrogen cycling

Mangrove ecosystems, where litter and organic components are degraded and converted into detrital materials, support rich coastal fisheries resources. Sesarmid (Grapsidae) crabs, which feed on mangrove litter, play a crucial role in material flow in carbon-rich and nitrogen-limited mangrove ecosystems; however, the process of assimilation and conversion into detritus has not been well studied. In this study, we performed microbiome analyses of intestinal bacteria from three species of mangrove crab and five sediment positions in the mud lobster mounds, including the crab burrow wall, to study the interactive roles of crabs and sediment in metabolism. Metagenome analysis revealed species-dependent intestinal profiles, especially in Neosarmatium smithi, while the sediment microbiome was similar in all positions, albeit with some regional dependency. The microbiome profiles of crab intestines and sediments were significantly different in the MDS analysis based on OTU similarity; however, 579 OTUs (about 70% of reads in the crab intestinal microbiome) were identical between the intestinal and sediment bacteria. In the phenotype prediction, cellulose degradation was observed in the crab intestine. Cellulase activity was detected in both crab intestine and sediment. This could be mainly ascribed to Demequinaceae, which was predominantly found in the crab intestines and burrow walls. Nitrogen fixation was also enriched in both the crab intestines and sediments, and was supported by the nitrogenase assay. Similar to earlier reports, sulfur-related families were highly enriched in the sediment, presumably degrading organic compounds as terminal electron acceptors under anaerobic conditions. These results suggest that mangrove crabs and habitat sediment both contribute to carbon and nitrogen cycling in the mangrove ecosystem via these two key reactions.

Marine microbial L-glutaminase: from pharmaceutical to food industry

Deamination of L-glutamine to glutamic acid with the concomitant release of ammonia by the activity of L-glutaminase (L-glutamine amidohydrolase EC 3.5.1.2) is a unique reaction that also finds potential applications in different sectors ranging from therapeutics to food industry. Owing to its cost-effectiveness, rapidity, and compatibility with downstream processes, microbial production of L-glutaminase is preferred over the production by other sources. Marine microorganisms including bacteria, yeasts, and moulds have manifested remarkable capacity to produce L-glutaminase and, therefore, are considered as prospective candidates for large-scale production of this enzyme. The main focus of this article is to provide an overview of L-glutaminase producing marine microorganisms, to discuss strategies used for the lab- and large-scale production of these enzyme and to review the application of L-glutaminase from marine sources so that the future prospects can be understood. KEY POINTS: • L-glutaminase has potential applications in different sectors ranging from therapeutics to food industry • Marine microorganisms are considered as prospective candidates for large-scale production of L-glutaminase • Marine microbial L-glutaminase have great potential in therapeutics and in the food industry.

Marine Bacterial Esterases: Emerging Biocatalysts for Industrial Applications

The marine ecosystem has been known to be a significant source of novel enzymes. Esterase enzymes (EC 3.1.1.1) represent a diverse group of hydrolases that catalyze the cleavage and formation of ester bonds. Although esterases are widely distributed among marine organisms, only microbial esterases are of paramount industrial importance. This article discusses the importance of marine microbial esterases, their biochemical and kinetic properties, and their stability under extreme conditions. Since culture-dependent techniques provide limited insights into microbial diversity of the marine ecosystem, therefore, genomics and metagenomics approaches have widely been adopted in search of novel esterases. Additionally, the article also explains industrial applications of marine bacterial esterases particularly for the synthesis of optically pure substances, the preparation of enantiomerically pure drugs, the degradation of human-made plastics and organophosphorus compounds, degradation of the lipophilic components of the ink, and production of short-chain flavor esters.

A critical review on marine serine protease and its inhibitors: A new wave of drugs?

Marine organisms are rich sources of enzymes and their inhibitors having enormous therapeutic potential. Among different proteolytic enzymes, serine proteases, which can be obtained from various marine organisms show a potential to biomedical application as thrombolytic agents. Although this type of proteases plays a crucial role in almost all biological processes, their uncontrolled activity often leads to several diseases. Accordingly, the actions of these types of proteases are regulated by serine protease inhibitors (SPIs). Marine SPIs control complement activation and various other physiological functions, such as inflammation, immune function, fibrinolysis, blood clotting, and cancer metastasis. This review highlights the potential use of serine proteases and their inhibitors as the new wave of promising drugs.

Structural insight into a GH1 β-glucosidase from the oleaginous microalga, Nannochloropsis oceanica

Marine microalgae are promising sources of novel glycoside hydrolases (GHs), which have great value in biotechnical and industrial applications. Although many GH1 family β-glucosidases have been extensively studied, studies on β-glucosidases from microalgae are rare, and no structure of algal GH1 β-glucosidase has been reported. Here, we report the biochemical and structural study of a GH1 β-glucosidase BGLN1 from Nannochloropsis oceanica, an oleaginous microalga. Phylogenetic analysis of BGLN1, together with the known structures of GH1 β-glucosidases, has indicated that BGLN1 is branched at the root of the eukaryotic part of the phylogenetic tree. BGLN1 showed higher activity against laminaribiose compared to cello-oligosaccharides. Unlike most of the other GH1 β-glucosidases, BGLN1 is partially inhibited by metal ions. The crystal structure of BGLN1 revealed that BGLN1 adopts a typical (α/β)₈-barrel fold with variations in loops and N-terminal regions. BGLN1 contains extra residues at the N-terminus, which are essential for maintaining protein stability. BGLN1 has a more acidic substrate-binding pocket than other β-glucosidases, and the variations beyond the conserved -1 site determine the substrate specificity. These results indicate that GH enzymes from microalgae may have unique structural and functional features, which will provide new insight into carbohydrate synthesis and metabolism in marine microalgae.