Engineered yeast for enzymatic hydrolysis of laminarin from brown macroalgae

From algae to advancements: laminarin in biomedicine

Laminarin, a complicated polysaccharide originating from brown algae, has emerged as a compelling candidate in the domain of biomedical research. This enigmatic molecule, composed of glucose units associated with both β-1,3 and β-1,6 glycosidic bonds, possesses an array of remarkable characteristics that render it auspicious for multifaceted biomedical applications. This review investigates the comprehensive potential of laminarin in the biomedical domain, emphasizing its remarkable biocompatibility, low cytotoxicity, and cell proliferation support. Laminarin's immunomodulatory attributes position it as an encouraging contender in immunotherapy and the development of vaccines. Moreover, its anti-inflammatory and antioxidant characteristics provide a promising avenue for combatting conditions associated with oxidative stress. In particular, laminarin excels as a drug delivery vehicle owing to its exceptional encapsulation capabilities emerging from its porous framework. Integrating pH and redox responsiveness in laminarin-based drug delivery systems is poised to redefine targeted therapies. Laminarin substantially contributes to tissue engineering by improving adhesion, migration of cells, and deposition of extracellular matrix. This augmentation magnifies the regenerative capability of tissue-engineered constructs, substantiated by the advancement of laminarin-based wound dressings and tissue scaffolds, marking considerable progress in the domain of wound healing and tissue regeneration. While laminarin exhibits substantial potential in biomedical applications, it remains in the initial phases of exploration. Comprehensive preclinical and clinical research is warranted to verify its effectiveness and safety across various applications. In essence, laminarin, a marine marvel, has the capability to remodel biomedical research, offering inventive solutions to complex difficulties.

Advances in oligosaccharides production from brown seaweeds: extraction, characterization, antimetabolic syndrome, and other potential applications

Brown seaweeds are a promising source of bioactive substances, particularly oligosaccharides. This group has recently gained considerable attention due to its diverse cell wall composition, structure, and wide-spectrum bioactivities. This review article provides a comprehensive update on advances in oligosaccharides (OSs) production from brown seaweeds and their potential health applications. It focuses on advances in feedstock pretreatment, extraction, characterization, and purification prior to OS use for potential health applications. Brown seaweed oligosaccharides (BSOSs) are extracted using various methods. Among these, enzymatic hydrolysis is the most preferred, with high specificity, mild reaction conditions, and low energy consumption. However, the enzyme selection and hydrolysis conditions need to be optimized for desirable yield and oligosaccharides composition. Characterization of oligosaccharides is essential to determine their structure and properties related to bioactivities and to predict their most suitable application. This is well covered in this review. Analytical techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC), and nuclear magnetic resonance (NMR) spectroscopy are commonly applied to analyze oligosaccharides. BSOSs exhibit a range of biological properties, mainly antimicrobial, anti-inflammatory, and prebiotic properties among others. Importantly, BSOSs have been linked to possible health advantages, including metabolic syndrome management. Metabolic syndrome is a cluster of conditions, such as obesity, hypertension, and dyslipidemia, which increase the risk of cardiovascular disease and type 2 diabetes. Furthermore, oligosaccharides have potential applications in the food and pharmaceutical industries. Future research should focus on improving industrial-scale oligosaccharide extraction and purification, as well as researching their potential utility in the treatment of various health disorders.[Figure: see text].

Sustainable circular biorefinery approach for novel building blocks and bioenergy production from algae using microbial fuel cell

The imminent need for transition to a circular biorefinery using microbial fuel cells (MFC), based on the valorization of renewable resources, will ameliorate the carbon footprint induced by industrialization. MFC catalyzed by bioelectrochemical process drew significant attention initially for its exceptional potential for integrated production of biochemicals and bioenergy. Nonetheless, the associated costly bioproduct production and slow microbial kinetics have constrained its commercialization. This review encompasses the potential and development of macroalgal biomass as a substrate in the MFC system for L-lactic acid (L-LA) and bioelectricity generation. Besides, an insight into the state-of-the-art technological advancement in the MFC system is also deliberated in detail. Investigations in recent years have shown that MFC developed with different anolyte enhances power density from several µW/m² up to 8160 mW/m². Further, this review provides a plausible picture of macroalgal-based L-LA and bioelectricity circular biorefinery in the MFC system for future research directions.

Gluco-oligosaccharides as potential prebiotics: Synthesis, purification, structural characterization, and evaluation of prebiotic effect

Prebiotics have long been used to modulate the gut microbiota and improve host health. Most established prebiotics are nondigestible carbohydrates, especially short-chain oligosaccharides. Recently, gluco-oligosaccharides (GlcOS) with 2-10 glucose residues and one or more O-glycosidic linkage(s) have been found to exert prebiotic potentials (not fully established prebiotics) because of their selective fermentation by beneficial gut bacteria. However, the prebiotic effects (non-digestibility, selective fermentability, and potential health effects) of GlcOS are highly variable due to their complex structure originating from different synthesis processes. The relationship between GlcOS structure and their potential prebiotic effects has not been fully understood. To date, a comprehensive summary of the knowledge of GlcOS is still missing. Therefore, this review provides an overview of GlcOS as potential prebiotics, covering their synthesis, purification, structural characterization, and prebiotic effect evaluation. First, GlcOS with different structures are introduced. Then, the enzymatic and chemical processes for GlcOS synthesis are critically reviewed, including reaction mechanisms, substrates, catalysts, the structures of resultant GlcOS, and the synthetic performance (yield and selectivity). Industrial separation techniques for GlcOS purification and structural characterization methods are discussed in detail. Finally, in vitro and in vivo studies to evaluate the non-digestibility, selective fermentability, and associated health effects of different GlcOS are extensively reviewed with a special focus on the GlcOS structure-function relationship.

Valorisation of the invasive alga Rugulopteryx okamurae through the production of monomeric sugars

Rugulopteryx okamurae is an invasive brown alga causing severe environmental and economic problems on the western Mediterranean coasts. Thus, in addition to the difficulties caused to the fishing and tourism sectors, there is a need to manage its accumulation on the beaches. This work aims to valorise this waste by using it as raw material for producing monosaccharides through a two-stage sequential process. These sugars could be used for different fermentative processes to obtain high-value-added bioproducts. In this work, biological pretreatment of the previously conditioned seaweed with the fungus Aspergillus awamori in solid-state fermentation (SSF), followed by enzymatic hydrolysis with a commercial enzyme cocktail, was performed. The effect of the extension of the biological pretreatment (2, 5, 8 and 12 days) on the subsequent release of total reducing sugars (TRS) in the enzymatic hydrolysis stage was studied. To analyse this effect, experimental data of TRS produced along the hydrolysis were fitted to simple first-order kinetics. Also, the secretion of cellulase and alginate lyase by the fungus, along with the biological pretreatment, was determined. The results suggest that 5 days of biological pretreatment of the macroalgae with A. awamori followed by enzymatic saccharification for 24 h with Cellic CTec2® (112 FP units/g of dry biomass) are the best conditions tested, allowing the production of around 240 g of TRS per kg of dried biomass. The main sugars obtained were glucose (95.8 %) and mannitol (1.5 %), followed by galactose (1 %), arabinose (0.9 %) and fucose (0.5 %). KEY POINTS: • Five-day SSF by A. awamori was the best condition to pretreat R. okamurae. • Five-day SSF was optimal for alginate lyase production (1.63 ±0.011 IU/g biomass). • A maximum yield of 239 mg TRS/g biomass was obtained (with 95.8 % glucose).

Sustainable production of biofuels and bioderivatives from aquaculture and marine waste

The annual global fish production reached a record 178 million tonnes in 2020, which continues to increase. Today, 49% of the total fish is harvested from aquaculture, which is forecasted to reach 60% of the total fish produced by 2030. Considering that the wastes of fishing industries represent up to 75% of the whole organisms, the fish industry is generating a large amount of waste which is being neglected in most parts of the world. This negligence can be traced to the ridicule of the value of this resource as well as the many difficulties related to its valorisation. In addition, the massive expansion of the aquaculture industry is generating significant environmental consequences, including chemical and biological pollution, disease outbreaks that increase the fish mortality rate, unsustainable feeds, competition for coastal space, and an increase in the macroalgal blooms due to anthropogenic stressors, leading to a negative socio-economic and environmental impact. The establishment of integrated multi-trophic aquaculture (IMTA) has received increasing attention due to the environmental benefits of using waste products and transforming them into valuable products. There is a need to integrate and implement new technologies able to valorise the waste generated from the fish and aquaculture industry making the aquaculture sector and the fish industry more sustainable through the development of a circular economy scheme. This review wants to provide an overview of several approaches to valorise marine waste (e.g., dead fish, algae waste from marine and aquaculture, fish waste), by their transformation into biofuels (biomethane, biohydrogen, biodiesel, green diesel, bioethanol, or biomethanol) and recovering biomolecules such as proteins (collagen, fish hydrolysate protein), polysaccharides (chitosan, chitin, carrageenan, ulvan, alginate, fucoidan, and laminarin) and biosurfactants.

Macroalgal biomass as a potential resource for lactic acid fermentation

Lactic acid is an essential platform chemical with various applications in the chemicals, food, pharmaceutical, and cosmetic industries. Currently, the demand for lactic acid is driven by the role of lactic acid as the starting material for the production of bioplastic polylactide. Microbial fermentation for lactic acid production is favored due to the production of enantiomerically pure lactic acid required for polylactide synthesis, as opposed to the racemic mixture obtained via chemical synthesis. The utilization of first-generation feedstock for commercial lactic acid production is challenged by feedstock costs and sustainability issues. Macroalgae are photosynthetic benthic aquatic plants that contribute tremendously towards carbon capture with subsequent carbon-rich biomass production. Macroalgae are commercially cultivated to extract hydrocolloids, and recent studies have focused on applying biomass as a fermentation feedstock. This review provides comprehensive information on the design and development of sustainable and cost-effective, algae-based lactic acid production. The central carbon regulation in lactic acid bacteria and the metabolism of seaweed-derived sugars are described. An exhaustive compilation of lactic acid fermentation of macroalgae hydrolysates revealed that lactic acid bacteria can effectively ferment the mixture of sugars present in the hydrolysate with comparable yields. The environmental impacts and economic prospects of macroalgal lactic acid are analyzed. Valorization of the vast amounts of spent macroalgal biomass residue post hydrocolloid extraction in a biorefinery is a viable strategy for cost-effective lactic acid production.

Marine Polysaccharides: Occurrence, Enzymatic Degradation and Utilization

Macroalgae species are fast growing and their polysaccharides are already used as food ingredient due to their properties as hydrocolloids or they have potential high value bioactivity. The degradation of these valuable polysaccharides to access the sugar components has remained mostly unexplored so far. One reason is the high structural complexity of algal polysaccharides, but also the need for suitable enzyme cocktails to obtain oligo- and monosaccharides. Among them, there are several rare sugars with high value. Recently, considerable progress was made in the discovery of highly specific carbohydrate-active enzymes able to decompose complex marine carbohydrates such as carrageenan, laminarin, agar, porphyran and ulvan. This minireview summarizes these achievements and highlights potential applications of the now accessible abundant renewable resource of marine polysaccharides.