• Research Outcomes

Research Outcomes

From 2009 to 2011 Dr Alastair Sutherland and his team - Dr Alan Williams (Senior Research Fellow) and Sue Withers (Senior Research Technician) - examined the possibility of using the rumen microbes of North Ronaldsay sheep to hydrolyse brown seaweeds. This study was supported by a Scottish Government grant of £147,000 from iTi Energy Seaweed Anaerobic Digestion programme.

The male North Ronaldsay Sheep, in particular, spend most of their lives walled off from the island’s pasture land and instead feed solely on seaweeds. The group considered that ruminants eating seaweed will have evolved anaerobic microbiota over thousands of years that very efficiently degrade seaweed polysaccharides; for it is only in doing so that they can rapidly and efficiently obtain the VFAs they require for energy utilisation. The  group have therefore recently isolated and shown that rumen bacteria from seaweed-eating North Ronaldsay sheep includes bacterial species that are highly hydrolytic for seaweed polysaccharides and are very effective in both the acidogenic and acetogenic phases of anaerobic digestion (AD) in vitro, as well as in methanogenesis

Williams, A.G., Withers, S. and Sutherland, A.D.* (2013) The potential of bacteria isolated from ruminal contents of seaweed-eating North Ronaldsay Sheep to hydrolyse seaweed components and produce methane by anaerobic digestion in vitro. Microbial Biotechnol. Vol 6 (1) p45-52.


Image courtesy of john bateson, Creative Commons license

There was now a need to compare this consortium with other potential inocula such as grass eating sheep microbes, human sewage anaerobic digester leachate, marine sediments and those from naturally degrading seaweeds in lab scale fermenters to find what an optimum inoculum is for AD of seaweed.

Studies carried out at CCMAR, Portugal have shown that in mini-fermenters a mixture of several microbial inocula (including North Ronaldsay sheep microbes) was more efficient than any individual inoculum in methane production by anaerobic digestion of Laminaria hyperborea (results to be published).

Gas collector and fermenter

G‌as collector and fermenter

Metagenomic analysis using microbial DNA from the various inoculum has been conducted and DGGE gels and pyrosequencing resuts are continuing to be analysed.

Dr Sutherland’s group at GCU found that the brown seaweeds Ascophyllum nodosum and Fucus serratus were, unlike L.hyperborea, toxic to North Ronaldsay sheep microbes and prevented AD.

Recent studies at CCMAR have shown that the mixed inoculum that was so successful in AD of L.hyperborea was however also susceptible to toxicity by the brown seaweeds Ascophyllum nodosum and Fucus serratus. However, this toxicity was shown to be related to high phlorotannin concentrations in these seaweeds and it was successfully neutralised by precipitation or removal of these (results to be published).