Microalgae


Microalgal biorefinery

Microalgal processes and the produced biomass are highly applicable to a biorefinery concept. The metabolic and biochemical flexibility of microalgae allows the production of a range of compounds simultaneously that can then be refined in to both high-value metabolites and bulk chemicals. Bioenergy feedstocks, such as oils and starch from microalgae still receive considerable attention from both academia and industry, but due to poor economics compared crude oil derived products, the development of processes producing alternative higher-value products has been necessitated.
Growth in the markets for high-value compounds derived from microalgae (including carotenoids and antioxidants, PUFA or bioactive metabolites) has also increased substantially over the past decade and is the main focus of commercial operations. Other bulk products include protein-rich feed for humans or animal nutrition, biomaterials, such as bioplastics, or as substrates for fermentative processes producing platform chemicals. These bulk products may be produced from the residues following extraction of higher-value compounds. This approach will maximise the value obtained from production processes, considering the biomass as a source of several refinable products is now commonplace, possibly resulting in improved and more stable revenues.
The extraction of different products from the microalgae should then follow an order and protocol whereby the compounds with the highest value are the main priority, possibly being extracted first using mild techniques to preserve their structure or function. The remaining ‘bulk’ residuals can then be further processed for other applications. There is now a growing sub-section of this field exploring the extraction or ‘refining’ of the whole biomass to release maximum value from produced materials, with new equipment and techniques concurrently being developed.
Microalgal production also offer several opportunities and benefits for integration or co-location with existing industrial or bio-processes. For example, the utilization of waste nutrients (CNP) and CO2 from processes such as anaerobic digestions or hydrothermal liquefaction, reduces costly input requirements and improves the sustainability of the whole biorefinery.

Projects:

Algae in the BioBUF project
Researchers: Joshua Mayers, Eva Albers

Production and valorisation of algal biomass into high-value metabolites and bulk materials in an integrated biorefinery alongside fermentative and forestry bioprocesses.

Carbohydrate-rich marine microalgae for a biorefinery
Researchers: Joshua Mayers, Eva Albers

Microalgae offer a large potential to be a sustainable and renewable feedstock for a bio-based production. Our aim for this project is to investigate processes for optimal and sustainable production of carbohydrates from marine microalgal biomass. This will be done by identifying potential high-carbohydrate containing strains, identifying optimal cultivation conditions, using CO2 from flue gas streams for cultivation, and evaluating potential applications based on sugar composition.


Microalgal cultivation

Microalgal growth requires a carbon source macronutrients, including N and P, and light and suitable cultivation system providing suitable conditions, e.g. with temperature and pH control. Algal cultivation is not currently economically feasible for many bulk commodities (i.e. biodiesel) and a reduction of costs is needed to realise these technologies. One way to reduce costs is to use waste streams for the supply of essential nutrients and water, reducing reliance on costly and energetically intensive fertilisers and freshwater inputs. This can include industrial process water, effluent of biological water treatment or other waste water streams that could also contain many micronutrient and organic carbon sources. Flue gases can also be used to provide carbon dioxide at the high concentrations needed for efficient growth and attainment of high cell densities in the cultivation system. However, other components in waste waters and flue gases can give negative effects and different streams may not contain sufficient amounts of nutrients, they should subsequently be carefully characterised on a case-by-case basis. In addition, the assimilation of organic carbon by microalgal can occur concurrently with photosynthetic CO2 fixation (mixotrophy), resulting in higher growth rates and increased maximum biomass concentration compared to photosynthesis alone. In terms of mixotrophic feedstocks, we currently investigate the use of more sustainable residual organic carbon sources such as crude glycerol (from biodiesel production), and xylose and organic acids from the forestry industry.

We aim with our work to better understand the feasibility of using different waste streams and emissions as a source of essential nutrients for microalgal biomass productivity, the effect on biochemical composition, and in addition the effects of additional and sometimes ‘unwanted’ components in these streams on growth and composition.

Projects:

Carbohydrate-rich marine microalgae for a biorefinery
Researchers: Joshua Mayers, Eva Albers

Utilizing industries’ residual resources as nutrients
Researchers: Mathias Bark, Eva Albers

The project aims to investigate how residual resources from industries can be used as nutrition for algae and deals with challenges for large-scale algal cultivations. The research investigates how such challenges can be overcome to efficiently produce algae biomass. This is a collaborative industrial PhD student project together with SP Technical Research Institute of Sweden in Borås.


Microalgal physiology and metabolism

Microalgae are a hugely diverse group of organisms (>100,000 species), represented across three different kingdoms and are found in an extraordinary range of habitats, including marine, fresh-water environments, but also extremes such as Antarctic ice, hot-springs and salt lakes. They subsequently have a huge diversity and flexibility with regards to their morphology, physiology (including photosynthesis) and biochemistry to help survive in their often turbulent or inhospitable habitats. The shifts in the composition of the molecules produced by some microalgae in response to stress is not just fascinating from an ecological and biochemical perspective, but is also of significant interest for those wishing to produce compounds from microalgae.
To maximise production of a particular metabolite, a detailed understanding of how the cell alters its biochemical pathways and metabolism under particular cultivation conditions or stress, is fundamental in improving the cell culture processes and formation of target metabolites. The most commonly tested condition is that of nitrogen starvation, used to induce accumulation of triacylglycerides. By measuring the abundance of specific intermediate metabolites and end-products (metabolomics) we are able to discern patterns in the allocation of carbon (CO2 via photosynthesis or carbon from organic sources) and nitrogen to different biochemical pathways. This may also indicate rate-limiting steps for target metabolites, suggesting targets for future genetic manipulation. 
We look to analyse in detail, the effect of different stresses or culture conditions on biochemical pathways and physiology, hoping to improve fundamental understanding of algal biology and apply this knowledge to applied systems. This approach is currently applied to projects concerning pigment over-accumulation, the effect of growth on sustainable organic carbon sources (mixotrophy) and the production of carbohydrate-rich biomass using marine species.

Projects:

Algae in the BioBUF project
Researchers: Joshua Mayers, Eva Albers

Carbohydrate-rich marine microalgae for a biorefinery
Researchers: Joshua Mayers, Eva Albers

Published: Thu 09 Jul 2015. Modified: Mon 19 Sep 2016