White Rose BBSRC DTP PhD Studentship Network in Industrial Biotechnology and Bioenergy: Growing

White Rose BBSRC DTP PhD Studentship Network in Industrial Biotechnology and Bioenergy

Network Title: Exploiting the Value of the Extremophilic Red Alga Galdieria for Industrial Biotechnological Benefits

Specific Project: Growing Galdieria in Photobioreactors using Microbubbles and Mixotrophy to Increase Growth rates and Biomass

Principal Supervisor: Dr Jim Gilmour, University of Sheffield
Secondary Supervisor: Dr James Chong, University of Leeds

Galdieria is a red alga that exhibits wide metabolic versatility and display enormous capacity to thrive at highly acidic conditions (down to pH 0) and temperatures above 55 ˚C, which is the theoretical limit of eukaryotic life. Members in this genus display broad metabolic repertoires allowing vigorous growth on virtually any sugar, sugar-alcohol or organic acid source and is capable of both photoautotrophic and chemoheterotrophic growth. Galdieria is a metabolic workhorse. It is know to detoxify contaminants under high concentrations of toxic metals. Its unique metabolic capacity evolved to facilitate endolithic growth under a mat of microorganisms, where it consumes lysed algae. The constellation of biochemical versatility in differing strains suggests a large repertoire of metabolic enzymes, which are potentially a rich source of thermo-stable proteins for biotechnology. The extremophile lifestyle of Galdieria makes it a fascinating organism to study from both a mechanistic viewpoint and to find those novel species with properties that have industrial biotechnological (IB) applications.

The industrial exploitation of microalgae and cyanobacteria is of great interest due to the novel compounds and potential products that they synthesise. To date, most successful industrial exploitation of microalgae and cyanobacteria has been achieved in open ponds using extremophilic microalgae, such as the halophilic Dunaliella and the alkalophilic cyanobacterium Spriulina. It is clear that the thermoacidophilic red microalga Galdieria has great promise as an industrial organism, but it is necessary to optimise its growth in photobioreactors (PBRs) and ponds to make this a reality. The usefulness of microbubbles has been demonstrated in a variety of algal systems and the effects are due to excellent gas exchange (CO2 in and O2 out) and highly efficient mixing to keep the cells in suspension and well illuminated. One of the key characteristics of Galdieria is its ability to grow fully heterotrophically in the dark in addition to the usual mode of algal growth (photoautotrophy using light and CO2 as the sole carbon source). Little is known about mixotrophic growth in Galdieria, and this mode of growth can combine the benefits of using light + CO2 with a fixed carbon source (e.g. waste glycerol from biodiesel production) to dramatically improve the biomass yield.

Selected Galdieria strains from the York collection will be chosen to represent the widest range of physiological and biochemical diversity and these strains will be grown in a range of PBRs. The effects of microbubbles will be measured in the small scale with numerous replicates and then scaled up to multi-litre PBRs. Parallel batch-culture flask experiments will optimise media for mixotrophy growth and the combined effect of mixotrophy and microbubbles will be determined in the 3 litre PBRs. Once a set of growth conditions is optimised in the multi-litre PBRs larger scale trials will be set up in a 250 litre PBR (available in Sheffield) and open ponds (available at Leeds). Metabolite and lipid-production levels would be assessed to maximise relationships of growth parameters to strain ideotype. Together this realises the scale of industrial cultivation required to develop Galdieria as an IB organism.

The Gilmour lab has excellent algal growth facilities and access to facilities in Chemical and Biological Engineering (CBE). We have a state of the art Walz PAM chlorophyll fluorometer equipment to allow us to monitor a wide range of photosynthetic parameters. The novel, fluidic oscillators (designed by Prof Zimmerman, CBE, Sheffield) are available in the lab to generate the microbubbles. Expertise in lipid and pigment analysis is also available in the lab.

The student would be exposed to a range of culturing techniques from small-scale flask, to medium-level PBR, and finally, to large production scale PBRs and open ponds. A wide range of analytical techniques including pigment analysis, chlorophyll fluorescence and a number of biochemical techniques will be required. The student will also develop engineering skills, such as the development of novel fluidic oscillator technology to generate microbubbles. PBRs are very "hands on" and the student will be involved in building, designing and trouble-shooting these PBRs that scale from the small litres to hundreds of litres.

Funding Notes

The studentship is tenable for four years from session 2016/17 (starting around October 2016) and will provide Home/EU tuition fees, a maintenance grant paid at standard Research Council rates. The successful candidate will be based at the University of Sheffield within the Department of Molecular Biology and Biotechnology, but will be part of a network of three PhD students and six academic staff based at Leeds, Sheffield and York universities.