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Investigating the enzymatic hydrolysis of wheat straw and production of biogas fuel by microbial co-cultures of anaerobic fungi and methanogens

Project Description


Industrial anaerobic digestion (AD) can be used to convert a wide range of biomass sources (or feedstock) such as food-wastes, farm slurries, sewage sludge and purpose-grown agricultural crops into renewable biogas fuel. However, the use of food crops, purpose-grown for feeding AD installations (or alternative industrial biotechnology processes) is controversial in terms of both ethical and sustainable considerations. This is due to the potential competition with food-crop production caused by a shared requirement for arable land, fresh water and nutrient resources. In 2017 the British government responded to societal concerns by declaring that for an AD plant in the UK to qualify for financial feed-in-tariff rewards, at least 50% of the biogas produced must be attributable to feedstocks which meet sustainable criteria in terms of the land used for crop growth and life-cycle greenhouse gas emissions. One potentially suitable and low-cost feedstock is wheat straw. Approximately 10.2 Mt and over 500 Mt of wheat straw is produced each year in the UK and globally, respectively. However, due to containing a high lignocellulose content (which is recalcitrant) wheat straw is hydrolysed relatively slowly by acidogenic bacteria during conventional anaerobic digestion. The length of time taken for wheat straw hydrolysis influences both the size and cost associated with the AD system.

The substitution of acidogenic bacteria with anaerobic fungi has been identified as a potentially suitable technique to reduce the time required for enzymatic hydrolysis of wheat straw and therefore significantly reduce the cost of biogas production. Before the use of anaerobic fungi can be adopted for industrial AD and other lignocellulose fed biotechnology processes, it is imperative that we learn more about the importance of the symbiotic relationship which naturally exists between anaerobic fungi (which break down and consume wheat straw) and methanogens (which convert the fungal by-products to biomethane fuel).

Aims & Objectives

This PhD project will test the hypothesis that anaerobic fungi are able to perform enzymatic hydrolysis of wheat straw at a faster rate and to a greater extent in the presence of methanogens. The project will aim to characterise the biochemical and spatial relationships between methanogenic cells and anaerobic fungi and quantify the ability of co-cultures to enzymatically degrade the wheat straw. The objectives of this laboratory-based project are as follows:
(i) Describe the relationship between partial pressure of H2, organic acid concentration and hydrolysis of wheat straw by anaerobic fungi in the presence and absence of co-cultured methanogenic microorganisms
(ii) Identify metabolic shifts in anaerobic fungi caused by variations in environmental partial pressure of H2 and organic acid concentration
(iii) Compare the rate of wheat straw digestion between anaerobic fungi growing in isolation and in co-culture with methanogenic species
(iv) Provide details about the influence of spatial proximity between anaerobic fungi and methanogenic cells on the enzymatic hydrolysis of wheat straw

Through this project the student will receive the specialist knowledge and training required for the isolation, identification and growth of anaerobic fungi. This training will include a range of anaerobic microbiological techniques which are essential for working with defined cultures of anaerobic microorganisms. In addition, the successful candidate will develop their expertise in a wide range of biochemical analysis techniques, statistical analyses and gain an understanding of the technical challenges faced by industrial AD and lignocellulose biotechnology.

The supervision team also includes Prof. Michael Theodorou, Harper Adams University and Prof. Michelle O’Malley, University of California Santa Barbara.

Funding Notes

This is a studentship fully funded for three years and covers: (i) a tax-free annual stipend at the standard Research Council rate (£15,009 estimated for 2020 entry), (ii) research costs, and (iii) tuition fees at the UK/EU rate.

The start date is 1st February 2020.


ENTRY REQUIREMENTS: Students applying for postgraduate study in our Department should normally have obtained an upper second class honours degree (or equivalent). If your first language is not English you will need to show evidence that you meet our English language requirements. We welcome applications from students with backgrounds in any biological, chemical, and/or physical science, or students with mathematical backgrounds who are interested in using their skills in addressing biological questions.

How good is research at University of York in Biological Sciences?

FTE Category A staff submitted: 44.37

Research output data provided by the Research Excellence Framework (REF)

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