Mining the rumen microbes for lipase activity

N Scollan, S Huws & CJ Newbold

Coronary heart disease (CHD) is a major cause of illness in Britain, with around 100,000 deaths annually, resulting in 2.5 % of NHS hospital expenditure. The relationship between dietary fat and CHD are well established and many studies have contributed to the advice that saturated fatty acids (SFA) should not supply >0.10 of total energy intake, that polyunsaturated fatty acids (PUFA):SFA should be >0.45, and that n-6:n-3 PUFA should be <4 for the whole diet (Department of Health, 1994). Despite the fact that the ruminant diet is PUFA-rich, ruminant products are rich in SFA due to bacterial lipolysis and subsequent biohydrogenation of ingested PUFA within the rumen (Scollan et al., 2006).  Anaerovibrio lipolytica is a well known rumen lipolytic bacterium (Hungate 1966), nonetheless the lipases of this organism have not been characterised nor is the genome of this bacterium currently sequenced. Data regarding the lipolytic capacity of other rumen microbes is also scarce and the little that is available is based on a few culturable isolates. This project seeks to get a better understanding of the rumen bacterial lipases and the bacteria that possess them by creating a metagenomic library of the rumen bacteria, with the aim of isolating lipase activity and subsequently lipase sequences. In order to investigate which rumen bacteria possess these identified lipase sequences, microfuidic digital polymerase chain reaction (PCR) will be used. There will also be scope within this project to explore lipolytic capabilities of the rumen ciliates and fungi as well as testing the resultant hypothesis outlined below depending on the student. Dependant on the student’s interest there is also the possibility to create metagenomic libraries of different breeds or indeed different species of ruminants in order to compare lipase genes and the bacteria that possess them. Obtaining an in depth knowledge of the ruminal microbial lipases will lead to us to test the following hypothesis:

• Certain dietary interventions cause inhibition of the lipolytic bacteria and subsequently lipase expression leading to increase in PUFA content of ruminant products.
• Rumen microbes produce more effective lipases compared to those which are currently used within industry. This may lead to the use of these lipases within the industrial context.