Within biomass as a whole, the linkages which are present have been largely identified and elucidated, one of the key types off linkages and functionalities which have been identified are lignin-carbohydrate complexes (LCC). These are the major bonding patterns found in biomass between the carbohydrate (cellulose & hemicellulose) and lignin functionalities from extracted portions of biomass. One of the main bonding patterns within LCCs is phenyl glycosidic, where the C1 of the carbohydrate is bonded through an ether bond to an aromatic ring. The synthesis of such compounds which represent extracted portions of biomass have a carbohydrate portion and therefore will allow for water solubility and negates the need for organic solvents when probing depolymerisation studies.

Correction for ‘Biocatalytic conversion of lignin model oligomer using a laccase-mediator system’ by Christopher W. J. Murnaghan et al. , Green Chem. , 2024, 26 , 10851–10858, https://doi.org/10.1039/D4GC01720J.

The push toward a renewable society where the chemicals being used on a daily basis come from sources which are not going to be depleted within the next few decades is highly sought after. Biomass is one of the most promising opportunities to establish self-sustainability for the human race. This review article takes a look at some of the key methods which have been employed for the synthesis of important lignin model compounds, and the synthetic techniques are discussed throughout the first section. The second section of this review is focused on some of the major strategies for the conversion of lignin model compounds throughout the literature. This review serves as a good starting point for someone who is relatively new to the field of lignin model synthesis and valorization.

A two-step one-pot rapid microwave assisted method has been developed for the Baeyer-Villiger oxidation of biomass derived levoglucosenone (LGO) analogues. This method uses the acidic resin Amberlyst 15 as the catalyst and hydrogen peroxide as the oxidant in ethanol solution. A small library of C4-substituted LGO analogues have been synthesised and oxidised using this method giving high yields in short times in each case. The purity of the recovered products was very high removing the need for chromatographic separation.

The conversion of biomass towards value-added and platform chemicals has become the focus of extensive research these past two decades. One of the methods that has been increasingly studied is the use of semiconductor-mediated photocatalysis for biomass conversion. Titanium dioxide has previously been demonstrated to be an effective commercial catalyst for the cleavage of bonds within lignin and also cellulose and hemicellulose. Described herein is the deployment of TiO2 for the cleavage of bonds within two β-O-4 lignin model compounds, one bearing a ketone in the α-position and the other an alcohol. The presence of a ketone in the benzylic position in one of the models had a pronounced effect under photolytic conditions, e.g., in the absence of a photocatalyst but with irradiation present. The subsequent reduction of the benzylic ketone resulted in observed sensitivity towards the irradiation and solely photocatalytic conversion was achieved. In addition, reaction products are proposed, which demonstrate a feasible method for β-O-4 cleavage in native lignin extracts.

As a globally abundant source of biomass, lignocellulosic biomass has been the centre of attention as a potential resource for green energy generation and value-added chemical production. A key component of lignocellulosic biomass, lignin, which is comprised of aromatic monomers, is a potential feedstock for value added chemical production. The cleavage processes of the linkages between monomers to obtain high value products, however, requires significant investigation as it is a complex, non-facile process. This study focuses on the photocatalytic valorization of a β-5 lignin model compound, a key linkage in the lignin structure. It was found that greater yields of aromatic products were obtained from the photocatalytic conversion of β-5 lignin model compound using carbon nitride (CN) when compared to Evonik P25 titanium dioxide (TiO2). Products of the β-5 model compound photocatalytic conversion were determined and C-C bond cleavage was observed. It was also determined that the solvent participated in the reactions with the introduction of a cyano group to one of the products. Radical quenching experiments revealed that superoxide radicals participated in the CN photocatalytic conversion. These results reveal for the first time the products and possible mechanism of the photocatalytic transformation of β-5 model compounds using CN photocatalysis.

The use of the laccase enzyme from the fungus Trametes versicolor, coupled with the mediator 1-hydroxybenzotriazole (1-HBT) has been shown to be effective for the biocatalytic conversion of a hexameric lignin model compound containing three of the most common linkages found in native lignin. Cleavage of the model takes place over a 24 hours period predominantly at the beta-O-4 ether linkage to give a previously known beta-5 dimer intermediate which in turn was rapidly consumed to further degradation products. There is also mass spectrometric evidence of repolymerisation of the beta-5 dimer and other degradation intermediates to form higher oligomers. Mechanistic pathways to account for the major catalytic processes are proposed. Employment of laccase from Trametes versicolor effects considerable cleavage in beta-O-4 linkage of lignin model hexamer.

This paper investigates the catalytic hydrogenolysis of solid digestate from anaerobic digestion to extract biofuel.

Brown seaweeds are a rich source of carotenoids, particularly fucoxanthin, which has a wide range of potential health applications. Fucoxanthin fluctuates within and among seaweeds over time, frustrating efforts to utilise this resource. Thus, we require comprehensive analyses of long- and short-term concentrations across species in field conditions. Here, we used High Performance Liquid Chromatography to compare fucoxanthin content in four brown macroalgae, Ascophyllum nodosum, Fucus serratus , Fucus vesiculosus and Saccharina latissima , monthly for 1 year. F. serratus and F. vesiculosus had significantly higher fucoxanthin content (mg/g), which was highest in Spring (0.39 ± 0.04) and Autumn (0.45 ± 0.04) [mean (± SE)]. Two species, A. nodosum and F. serratus , were collected monthly at the same location for a further two non-consecutive years. For both A. nodosum and F. serratus , a significant interaction effect of seasons and years was identified, highlighting that there is variation in fucoxanthin content among and within species over time. We also show that fucoxanthin content differs significantly among months even within seasons. Therefore, it is not sufficient to assess fucoxanthin in single months to represent seasonality. We discuss how weather, nutrients and reproduction may have driven the seasonal variation, and reveal patterns of fucoxanthin concentration that can provide information concerning its availability for many important medical functions.

Lignin is the most abundant renewable feedstock to produce aromatic chemicals, however its depolymerisation involves the breaking of several C–O and C–C inter-unit linkages that connect smaller aromatic units that are present in lignin. Several strategies have been reported for the cleavage of the C–O inter-unit linkages in lignin. However, till today, only a few methodologies have been reported for the effective breaking or the conversion of the recalcitrant C–C inter unit linkages in lignin. Here we report the ruthenium ion catalysed oxidative methodology as an effective system to activate or convert the most recalcitrant inter unit linkages such as β-5 and 5–5′ present in lignin. Initially, we used biphenyl as a model compound to study the effectiveness of the RICO methodology to activate the 5–5′ C–C linkage. After 4 h reaction at 22 °C, we achieved a 30% conversion with 75% selectivity towards benzoic acid and phenyl glyoxal as the minor product. To the best of our knowledge this is the first ever oxidative activation of the C–C bond that connects the two phenyl rings in biphenyl. DFT calculation revealed that the RuO4 forms a [3 + 2] adduct with one of the aromatic C–C bonds resulting in the opening of the phenyl ring. Biphenyl conversion could be increased by increasing the amount of oxidant; however, this is accompanied by a reduction in the carbon balance because of the formation of CO2 and other unknown products. We extended this RICO methodology for the oxidative depolymerisation of lignin model hexamer containing β-5, 5–5′ and β-O-4 linkages. Qualitative and quantitative analyses of the reaction mixture were done using 1H, 13C NMR spectroscopy methods along with GC-MS and Gel Permeation Chromatographic (GPC) methods. Advanced 2D NMR spectroscopic methods such as HSQC, HMBC and 31P NMR spectroscopy after phosphitylation of the mixture were employed to quantitatively analyse the conversion of the β-5, 5–5′ and β-O-4 linkages and to identify the products. After 30 min, >90% of the 5–5′ and linkages and >80% of the β-5′ are converted with this methodology. This is the first report on the conversion of the 5–5′ linkage in lignin model hexamer.

Photocatalytic reforming of biomass has emerged as an area of significant interest within the last decade. The number of papers published in the literature has been steadily increasing with keywords such as ‘hydrogen’ and ‘visible’ becoming prominent research topics. There are likely two primary drivers behind this, the first of which is that biomass represents a more sustainable photocatalytic feedstock for reforming to value-added products and energy. The second is the transition towards achieving net zero emission targets, which has increased focus on the development of technologies that could play a role in future energy systems. Therefore, this review provides a perspective on not only the current state of the research but also a future outlook on the potential roadmap for photocatalytic reforming of biomass. Producing energy via photocatalytic biomass reforming is very desirable due to the ambient operating conditions and potential to utilise renewable energy (e.g., solar) with a wide variety of biomass resources. As both interest and development within this field continues to grow, however, there are challenges being identified that are paramount to further advancement. In reviewing both the literature and trajectory of the field, research priorities can be identified and utilised to facilitate fundamental research alongside whole systems evaluation. Moreover, this would underpin the enhancement of photocatalytic technology with a view towards improving the technology readiness level and promoting engagement between academia and industry.

Population growth is the driving change in the search for new, alternative sources of protein. Macroalgae (otherwise known as seaweeds) do not compete with other food sources for space and resources as they can be sustainably cultivated without the need for arable land. Macroalgae are significantly rich in protein and amino acid content compared to other plant-derived proteins. Herein, physical and chemical protein extraction methods as well as novel techniques including enzyme hydrolysis, microwave-assisted extraction and ultrasound sonication are discussed as strategies for protein extraction with this resource. The generation of high-value, economically important ingredients such as bioactive peptides is explored as well as the application of macroalgal proteins in human foods and animal feed. These bioactive peptides that have been shown to inhibit enzymes such as renin, angiotensin-I-converting enzyme (ACE-1), cyclooxygenases (COX), α-amylase and α-glucosidase associated with hypertensive, diabetic, and inflammation-related activities are explored. This paper discusses the significant uses of seaweeds, which range from utilising their anthelmintic and anti-methane properties in feed additives, to food techno-functional ingredients in the formulation of human foods such as ice creams, to utilising their health beneficial ingredients to reduce high blood pressure and prevent inflammation. This information was collated following a review of 206 publications on the use of seaweeds as foods and feeds and processing methods to extract seaweed proteins.

The valorization of biomass via photocatalysis is an area of expanding research with advances in new technologies and materials with a view toward enhanced sustainability being reported. A significant challenge within this field, however, is understanding the impact photocatalysis has on more recalcitrant compounds present in biomass, such as lignin. Moreover, the current state of lignin model compound research is still largely focused on the breakdown of small models containing typically only one linkage. Described herein is the use of TiO2-mediated photocatalysis for the degradation of a representative hexameric lignin model compound which contains multiple linkages (e.g., 5-5', β-5, and β-O-4). The results revealed that while cleavage of the β-5 and β-O-4 occurred, the 5-5' appeared to remain intact within the identified reaction intermediates. To understand some of the more fundamental questions, a dimeric compound with a biphenyl linkage was synthesized and studied under photocatalytic conditions. The proposal of intermediates and pathways of degradation based on the studies conducted is presented and discussed herein.

A life cycle thinking analysis (LCT) conducted on the production of vanillin via bamboo wet air oxidation compared to vanillin production from crude oil or kraft lignin.

The valorisation of lignin has gained significant interest in bioenergy, which is driven by the abundance of the material coupled with the potential to form value-added compounds. As a result, the range of technologies deployed for this application has increased and more recently includes advanced oxidation processes such as photocatalysis. The complexity of lignin is challenging however, and therefore model compounds, which represent key linkages in the native structure, have become crucial as both a tool for evaluating novel technologies and for providing an insight into the mechanism of conversion. Previously, the β- O-4 dimer, the most abundant linkage found in native lignin, has been extensively used as a model compound. Described herein, however, is the first report of photocatalytic TiO 2 technology for the degradation of a β- 5 model dimer. Under low power UV-light emitting diode irradiation, complete degradation of the β- 5 compound (6.3 × 10 −3 mg ml −1 min −1 ) was achieved along with formation and subsequent removal of reaction intermediates. Investigation into the mechanism revealed within the first 2 min of irradiation there was the formation of a diol species due to consumption of the alkene sidechain. Although the data presented highlights the complexity of the system, which is underpinned by multiple oxidative reaction pathways, an overview of the key photocatalytic processes are discussed including the impact of acetonitrile and role of reactive oxygen species.

Anaerobic digestion (AD) has become an effective waste management method in the agri-food sector to dispose of livestock and food wastes. As AD becomes more widely used new challenges emerge, such as the disposal of digestate by-products. Currently, the principal method for handling solid digestate (SD) is direct application to land as an organic fertiliser. However, as the sector grows, this option is less viable due to nutrition loading on the land and increased eutrophication. This paper explores the potential of using SD as a biofuel source. Additionally, the pyrolysis kinetic triplet of residual SD and thermal predictions was reported for the first time using Advanced Kinetics and Technology Solutions (AKTS) thermokinetics software to model and calculate the activation energy (E-a) and other kinetic parameters. ASTM-E698, Ozawa-Flynn-Wall and differential isoconversional (model-free) methods were used and the E a values calculated from each model were 169.8, 75 - 175.0, and 85 - 190.0 kJ mol(-1), respectively. The kinetic triplet can be used in the scale-up or designing of reactor systems considering SD as a feedstock. The kinetic prediction of isothermal pyrolysis of SD indicated that a temperature higher than 210 degrees C is required for onset of decomposition in the sample. Furthermore, SD has the potential to produce an additional similar to 27.9 MJ per day at a 500 kW standalone on-farm AD plant. This work has highlighted the potential of waste solid digestate as a potential solid biofuel that could add an additional revenue stream to AD plants and make them more sustainable.

Seaweeds offer a natural source of antimicrobials that may help curb antibiotic resistance in livestock. The antibacterial activity of phlorotannin extracts isolated from two brown seaweeds Ascophyllum nodosum and Fucus serratus was tested. The mechanism of action of phlorotannin extracts against Escherichia coli O157, Salmonella agona, and Streptococcus suis was elucidated by observing cell membrane permeability and intracellular adenosine triphosphate (ATP). The two extracts were effective at killing three foodborne pathogens without negatively affecting the pig intestinal cells. A. nodosum minimum inhibitory concentration (MIC) range for the different pathogens was between 1.56 and 0.78 mg/mL, whereas F. serratus was 3.13 mg/mL for all pathogens tested. A. nodosum was found to be much more potent compared to F. serratus. The difference in potency in the seaweeds may be a result of the phlorotannins' structural linkages. The antimicrobial properties of the seaweed extracts tested may provide alternative and complementary treatments to antibiotics and zinc oxide in animal feeds. The seasonal screening was performed on both species to assess the availability of phenolics throughout the year using two quantification methods, the Folin-Ciocalteu (FC) assay and quantitative nuclear magnetic resonance (NMR). The variation between the methods highlights the challenges involved in the quantification of complex phenolic structures. However, both methods show that the phenolics are subject to seasonal variation, which may prove problematic to the animal feed industry.

The valorisation of Anaerobic digestion waste streams into algal biomass to produce a protein alternative to soybeans could have significant commercial and environmental value. It has the benefit of alleviating the pressure of disposal of nutrient-rich digestate that is rich in nitrogen, phosphorous and trace metals, while potentially reducing the cost of microalgae production. Currently, the use of soybean protein in animal feed has significant negative environmental issues and high carbon footprint associated with its use. This study investigates three types of Anaerobic digestion to grow Phaeodactylum tricornutum Bohlin microalgae. The results found that the crude protein in all concentrations of cow waste and food waste digestates were found to produce a significantly higher concentration of crude protein in comparison to the F/2 control. In addition, cow waste 1% and pig waste 1% formulations were found to have favourable fatty acid profiles, which has significant health benefits in the livestock industry. There was no significant difference in the total fatty acids found in cow waste 1% and pig waste 1% digestates compared to the F/2 control, which was in the range of 243.4 to 269.4 mg/g (dry weight). The other formulations produced a significantly lower (p < .05) concentration of total fatty acids compared to the control. Cow waste 1% was found to be richer in omega-3, eicosapentaenoic acid, compared to pig waste 1%, however, no significant difference was found between the eicosapentaenoic acid, concentration of cow waste 1% and the F/2 control. Overall, in terms of highest total fatty acids and crude protein, cow waste 1% digestate was found to perform the best out of all the digestates tested, and outperformed the F/2 control in terms of crude protein. The P. tricornutum grown in digestate was also found to bioaccumulate higher levels of calcium. P. tricornutum grown in cow waste 1% digestate could offer an alternative viable locally grown protein source for the animal feed industry, with the added advantage of being rich in eicosapentaenoic acid and calcium.

Phlorotannins have been reported to have positive effects on pig health, including improved gut health and digestibility. In this study, we investigate the effect of phenolics found in two brown seaweeds, Ascophyllum nodosum and Fucus serratus, on in vitro dry matter digestibility of seaweeds and commercial pig feed. Phlorotannin extracts and whole seaweeds were supplemented into pig feed to test their effect on digestibility. Solid-phase extraction was used to purify the phenolics to phlorotannins. The results showed a slight decrease in the digestibility of pig feed that was found to be significant when phlorotannin extracts were added from either seaweed. However, when whole A. nodosum was added to the pig feed, the effect on digestibility was less pronounced. Specifically, no significant difference in digestibility was observed at inclusion rates up to 5%, and thereafter results varied. A difference in digestibility was also observed in the same species at the same inclusion rate, collected from different seasons. This suggests that other compounds, e.g., polysaccharides, are having an effect on digestibility when whole seaweeds are supplemented to animal feed. This research has also highlighted the need to base supplementation on phenolic concentration as opposed to a standardised percentage inclusion of seaweeds to ensure that digestibility is not adversely affected.

Marine drugs hold significantly more promise than their terrestrial counterparts, which could help to solve the current shortfall in treatments for osteoporosis and other bone related diseases. Fucoxanthin is the main carotenoid found in brown seaweed, and has many perceived health benefits, including potential bone therapeutic properties. This study assessed the osteogenic potential of pure fucoxanthin and crude extracts containing both fucoxanthin and phenolic fractions (also cited to have osteogenic potential) isolated from two intertidal species of brown seaweed, Laminaria digitata and Ascophyllum nodosum. In vitro studies were performed using a human foetal osteoblast cell line (hFOBs) and primary human bone marrow stromal cells (hBMSCs). The results found pure fucoxanthin inhibitory to cell proliferation in hFOBs at higher concentrations, whereas, the crude extracts containing both polyphenols and fucoxanthin showed the ability to scavenge free radicals, which masked this effect. None of the extracts tested showed strong pro-osteogenic effects in either cell type tested, failing to support previously reported positive effects.