Jessica Adams

Seasonal variation in Laminaria digitata and its impact on biochemical conversion routes to biofuels.

Laminaria digitata is a highly prevalent kelp growing off the coast of the UK but has rarely been considered as a source of biomass to date. This study shows it can be used as a feedstock in both ethanol fermentation and anaerobic digestion for methane production. The study optimised several parameters in the fermentation of L. digitata and investigated the suitability of the macroalgae through the year using samples harvested every month. For both methane and ethanol production, minimum yields were seen in material harvested in March when the carbohydrates laminarin and mannitol were lowest. July material contained the highest combined laminarin and mannitol content and maximum yields of 167 mL ethanol and 0.219 m(3) kg(-1)L. digitata.

Scanning electron microscopy and fermentation studies on selected known maize starch mutants using STARGEN™ enzyme blends

The conversion of maize (corn) kernels to bio-ethanol is an energy-intensive process involving many stages. One step typically required is the liquefaction of the ground kernel to enable enzyme hydrolysation of the starch to glucose. The enzyme blends STARGEN™ (Genencor) are capable of hydrolysing starch granules without liquefaction, reducing energy inputs and increasing efficiency. Studies were conducted on maize starch mutants amylose extender 1 (ae1), dull 1 (du1) and waxy 1 (wx1) in the inbred line Oh43 to determine whether different maize starches affected hydrolysation rates by STARGEN™ 001 and STARGEN™ 002. All mutants contained similar proportions of starch in the kernel but varied in the amylose to amylopectin ratio. Ground maize kernels were incubated with STARGEN™ 001 and viewed using scanning electron microscopy to examine the hydrolysis action of STARGEN™ 001 on the starch granules. The ae1 mutant exhibited noticeably less enzymic hydrolysis action, on the granules visualised, than wx1 and background line Oh43. Kernels were batch-fermented with STARGEN™ 001 and STARGEN™ 002. The ae1 mutant exhibited a 50% lower ethanol yield compared to the wx1 mutant and background line. A final study compared hydrolysation rates of STARGEN™ 001 and STARGEN™ 002 on purified maize starch, amylopectin and amylose. Though almost twice the amylopectin was hydrolysed using STARGEN™ 002 than STARGEN™ 001 in this trial, fermentations using STARGEN™ 002 resulted in lower ethanol yields than fermentations using STARGEN™ 001. Both STARGEN™ enzyme blends were more suitable for the fermentation of high amylopectin maize starches than high amylose starches.

Functional genomics of forage and bioenergy quality traits in the grasses

Biomass from forage and energy crops can provide a renewable source of meat, milk, and wool, or power, heat, transport fuels and platform chemicals, respectively. Whilst in forage grasses some improvements have been made, the potential of energy grasses is limited because plant varieties have not yet been selected for this purpose. There are distinct challenges to determine and improve quality traits which increase ultimate energy yield but experience from forage crops can help. Energy grasses offer the potential to be utilised through either thermal or biological conversion methods with the route chosen being largely determined by the calorific value, moisture content and the ratio of soluble to structural carbohydrates. Plant chemical composition underlies these characteristics, for example whichever way grass feedstocks are converted the major determinates of energy are lignin, cell wall phenolics and the soluble and cell wall carbohydrates. These components affect the efficiency of the energy conversion process to meat, milk, wool, energy, platform chemicals and the end quality of certain liquid fuels such as pyrolysis oils. To associate phenotype to genotype for such underlying chemical composition, it is necessary to develop both DNA based molecular markers and high throughput methods for compositional analysis. The genetic resources available in forage and energy grasses are limited in comparison with several model grasses including maize and for some traits it may be appropriate to work initially on such a model and then translate this research back to the forage or bioenergy crop. However not all traits will be present in the model, and so genetic and genomic resources are and will have to be developed in the crops themselves. As part of the EU project GRASP, SNP based markers have been developed in carbohydrate associated genes which map to soluble carbohydrate QTL in Lolium perenne (perennial ryegrass) and these have been used in association studies in a synthetic population of L. perenne to measure allele shifts. High throughput calibration models have been developed using near infrared reflectance spectroscopy (NIRS) and Fourier transform infrared spectroscopy (FTIR) in the mid-infrared spectral range which allow accurate predictions of a number of composition traits including lignin, cellulose and hemicellulose contents in several forage and energy grasses including Miscanthus, L. perenne and related species. These calibrations have allowed a comparison of chemical composition from different grass genotypes, species and environments. Both tools and genetic resources for the optimisation of biomass as forage and energy feedstocks are therefore being developed to enable association of phenotype with genotype.

Dewatering treatments to increase dry matter content of the brown seaweed, kelp (Laminaria digitata ((Hudson) JV Lamouroux)).

Macroalgal water content is an on-going problem for the use of readily accessible seaweeds in sustainable biorefining, including fuel production. Silage is a reduced-water, compactable, easily stored, transportable material. Ensiling could establish a non-seasonal supply of preserved algal biomass, but requires high initial dry matter content to mitigate environmental pollution risks from effluent. This study investigated potential dewatering methods for kelp harvested throughout the year. Treatments included air-drying, osmotic media and acids. Significant interactions between treatment and harvest-time were observed for traits of interest. Fresh weight loss during treatment was composed of changes in water and dry matter content. Air-drying gave reliable increase in final dry matter content; in summer and autumn 30% dry matter content was reached after 24h. Dilute hydrochloric acid reduced stickiness and rendered material suitable for dewatering by screw-pressing; it may be possible to use the consequent pH reduction to promote efficient preservation.

Metaphylogenomic and potential functionality of the limpet Patella pellucida's gastrointestinal tract microbiome.

This study investigated the microbial diversity associated with the digestive tract of the seaweed grazing marine limpet Patella pellucida. Using a modified indirect DNA extraction protocol and performing metagenomic profiling based on specific prokaryotic marker genes, the abundance of bacterial groups was identified from the analyzed metagenome. The members of three significantly abundant phyla of Proteobacteria, Firmicutes and Bacteroidetes were characterized through the literature and their predicted functions towards the host, as well as potential applications in the industrial environment assessed.

The effect of mechanical pre-processing and different drying methodologies on bioethanol production using the brown macroalga Laminaria digitata (Hudson) JV Lamouroux

Macroalgae are capable of generating more organic carbon per hectare than terrestrial plants without requiring land, fertiliser or fresh water to grow. In addition, they avoid the food versus fuel argument as they are not a major food source in Europe. In spite of these benefits, macroalgae are not yet fully exploited as a biomass source for bioenergy or platform chemical production in Europe, with one issue being the high harvesting and processing costs. This paper considers the impact of mechanical pre-processing of Laminaria digitata combined with different drying techniques and the effect of these on downstream processing to bioethanol. Results show that mechanically screw pressing macroalgae does enhance conversion to ethanol, but only when the material contains low levels of storage carbohydrates. This occurs in freeze-dried and air-dried samples. The addition of a press aid in the mechanical pre-processing step increases ethanol yields per gramme macroalgae, but due to the presence of the unutilised press aid in the fermentation, ethanol yields were lower overall. The two main findings from this work were (1) simple mechanical processing of L. digitata provides homogenisation and pumpability of macroalgae without negatively affecting subsequent microbial conversion to ethanol. (2) At higher carbohydrate concentrations, screw pressing confers no advantage in ethanol yields over strips of unprocessed kelp, making strips the more viable conversion option for low-input, large-scale processing.

Novel rapid method for the characterisation of polymeric sugars from macroalgae

Laminarins are storage polysaccharides found only in brown seaweeds, specifically Laminarialaes and Fucales. Laminarin has been shown to have anti-apoptotic and anti-tumoural activities and is considered as a nutraceutical component that can positively influence human health. The structure is species dependent, generally composed of linear ß(1–3) glucans with intrachain β(1–6) branching and varies according to harvest season and environmental factors. Current methods for analysis of molar mass and DP length are technically demanding and are not widely available. Here, we present a simple inexpensive method which enables rapid analysis of laminarins from macroalgal biomass using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) without the need for hydrolysis or further processing. This is based on the linear relationship observed between log10 DP and retention time following separation of laminarins on a CarboPac PA-100 column (Dionex) using standard 1,3-β-d-gluco-oligosaccharides ranging in DP from 2 to 8. This method was applied to analyse laminarin oligomers in extracts from different species harvested from within the intertidal zone on Welsh rocky shores containing laminarin polymers with different ranges of DP. The degree of polymerisation and extrapolated molar mass agreed well with values estimated by LC-ESI/MSn analysis and those reported in the literature.

Species variation in the effects of dewatering treatment on macroalgae

Seaweeds can be a valuable resource for biorefinery and biotechnology applications, but their high water content is a recurrent problem and one of the key bottlenecks for their sustainable use. Treatments to increase dry matter content of the kelp Laminaria digitata were recently described by the authors. However macroalgae are an extremely diverse group of organisms and compositional variation between species may influence the effects of particular treatments. In this study, potential dewatering treatments including drying, osmotic media, and the application of both organic and mineral acids all followed by screw-pressing have been tested on two other species of kelp (Laminaria hyperborea and Saccharina latissima) and a red seaweed (Palmaria palmata). Conditions that dewatered these species were identified and the data have been combined with the previous results for L. digitata. There were significant differences between species across all the traits of interest. However dewatering was highly dependent on specific interactions with both treatment and season of collection. Nevertheless, the dry matter content of brown seaweeds was widely and successfully increased by air drying or acid treatment followed by screw-pressing. The results for P. palmata were quite different, particularly with regard to juice production. For this species, acid treatment did not result in dewatering, but dry matter content could be increased by screw-pressing immediately after harvest. Together the data presented here demonstrate that dewatering pre-treatments need to be specific for the type of seaweed to be processed; important knowledge for the future use of this sustainable biomass resource.

What cell wall components are the best indicators for Miscanthus digestibility and conversion to ethanol following variable pretreatments

BackgroundEnergy crops including Miscanthus provide a storable, portable energy source which can be used to complement a wide range of products and energy generation systems. Miscanthus is predominantly used in Europe as a combustion material for electricity generation but also has the potential for biochemical conversion due to its high yield and low-nutrient requirements. The ratio of holocellulose (hemicellulose and cellulose combined) to acid detergent lignin (H:L) within the senesced material has previously been shown to indicate the relative suitability of Miscanthus accessions for thermochemical conversion. In this study, the ratio was assessed to examine its use as a selection aid for biochemical conversion. 20 highly-characterised Miscanthus accessions were saccharified using an enzyme mix to determine optimum sugar release. Nine of these accessions spanning high, medium and low H:L ratios were then autoclaved with dilute acid, alkali or water, and enzymically hydrolysed and fermented to produce ethanol. Samples taken throughout the process allowed assessments of released sugars.ResultsEnzymic degradation of the biomass showed a relationship between H:L ratio and glucose release, with high glucose release for high H:L ratio accessions and vice versa. Xylose release showed no such relationship. This relationship was maintained following pretreatments and enzyme saccharification, where compound analysis showed that following all pretreatments, accessions with high H:L ratios repeatedly had the highest releases of glucose, xylose and arabinose, and produced more ethanol. Release of all measured compounds increased with the pretreatment severity and ethanol yields from each pretreatment correlated with the respective glucose yield, providing assurance that any inhibitory compounds generated were tolerated by the fermentation yeast. Strong correlations were also seen between glucose release, ethanol and cell wall components, with cellulose showing the highest correlations with ethanol yields for some treatments and H:L ratio with others.ConclusionsThe H:L ratio is a good predictor of ethanol yields and sugar release from Miscanthus in this study but individual components lignin and cellulose also correlate well, especially for hot water and mild acid pretreatments. In conclusion, use of the H:L ratio does not provide any advantages over the concentration of individual cell wall components for predicting sugar release and ethanol yields.