Effect of rumen lipases on ruminal lipid metabolism (Presentation)

Student: Cate Williams
Company: Hybu Cig Cymru
Academic Supervisor: Dr Sharon Huws

The effect of rumen bacterial lipases on ruminal lipid metabolism

The relationship between SFAs and chronic diseases, such as coronary heart disease, are well established, and despite providing many essential vitamins and minerals, red meat suffers much negative stigma. This confusion has developed as we’ve increased consumption of processed and fatty cuts of red meat, which contain more saturated fat, sugar and salt, and fewer essential nutrients.

As such, this project aims to reduce the saturated fat content of red meat, to balance essential nutrients with health detrimental saturated fat (SFA). In the western world, this would mean we could continue benefitting from the essential nutrients red meat provides, whilst cutting down our SFA intake, thus improving public health. In developing countries, where the majority of the population increase is predicted to occur, the good nutrient profile of red meat, as well as its lower premium and increased availability, will present a potential solution to the looming food crisis.

Ruminants, most commonly cattle and sheep, are named so due to their complex digestive system, the first compartment of which is the rumen. The rumen is filled with a diverse population of microorganisms, including bacteria.

Despite the ruminant diet being rich in health beneficial polyunsaturated fatty acids (PUFAs), meat and milk are high in SFA. This is due to the activity of bacteria and their enzymes (lipases) in the rumen, where food particles undergo two processes – lipolysis and biohydrogenation. During lipolysis, lipases break down ingested PUFA into free fatty acids, which are converted to SFAs during the biohydrogenation process. Free fatty acids (FFAs) are toxic to the microorganisms of the rumen, so this project focuses on either building up these FFAs to reduce biohydrogenation, or inhibiting the enzymes that produce FFAs. If a robust and efficient chemical inhibitor could be identified, then lipases would not be able to provide FFAs for biohydrogenation, reducing the amount of SFAs available for absorption.

Thus far, a batch culture experiment using fresh rumen fluid and 5 different concentrations of PUFA has allowed us to assess whether biohydrogenation can be inhibited. Samples were taken at 4 different time points and the resulting fatty acid profile assessed. It was found that medium levels (250-500μM) of PUFA were most effective in reducing the saturated fat and enhancing PUFA content of samples. RNA profiling is also underway, which will allow us to genetically identify microbial communities within each sample.

After comparing the most efficient concentrations of PUFA used in the batch experiment to those in typical ruminant diets, it is clear that enhancing PUFA in forage would not be successful due to the drip feeding nature of ruminant consumption. Biohydrogenating bacteria also completely recover function as soon as 8 hours, so feeding PUFA as a protected additive probably wouldn’t be very effective either.

As such, we will now explore the possibility of using a chemical inhibitor of ruminal and commercial lipases we have in existing libraries.