Omega 3 is an essential fatty acid for humans. It has many important health benefits and is thought to be particularly important during early brain development. The term essential, refers to the fact that mammals are unable to produce this group of fatty acids themselves and are completely dependent on obtaining them from their diet. Currently, oily fish is the major commercial source of omega 3 but with increasing pressure on fish stocks, a lot of research has gone into finding an alternative source. Marine algae have been well studied as such a source as the omega 3 found in fish oils originate from microbes anyway. Another important aspect of these studies is the development of a commercially viable method of growing and harvesting them.
A byproduct of biodiesel manufactured from crops and microbes is crude glycerol which is heavily contaminated with soap and methanol. To purify the glycerol requires an expensive process which makes it inappropriate for use in other industries, like food and pharmaceuticals. As the biodiesel industry increases in size so does the amount of crude glycerol production so finding a way to utilise it could be beneficial.
In this study, a marine microalgae called Schizochytrium limacinum was grown because of its ability to produce one particular omega 3, docosahexaenoic acid (DHA) through fermentation. In the growth medium, the authors used crude glycerol as an energy source which they had obtained from a biodiesel refinery. As any industrial harvesting of DHA would require destruction of the cells, it is vital to maximise the growth rate by constantly adding more medium to the cell culture, which dilutes it but maintains exponential growth. As media is added, the same amount of cell suspension is pumped out for processing. It is basically a large container with an over-flow pipe and a stirring impeller. Maintaining a high composition of DHA within the cells is also important. The objective of this study was to examine the growth efficiency of S. limacinum, efficiency of crude glycerol utilisation and DHA production. This was achieved by taking daily samples from the run-off cell suspension after a number of different media dilutions and crude glycerol concentrations were used.
Results indicated that biomass productivity was maximum when approximately 30% of extra media was added daily, giving 3.88 g/L of biomass from the run off cell suspension. Maximum DHA yield (0.52 g/L/day) was also measured at the same dilution rate when the medium contained 90 g/L of crude glycerol. If crude glycerol concentration was higher than 90 g/L the DHA content decreased sharply for some unknown reason.
In conclusion, this method of DHA production for possible use as a dietary supplement seems a good alternative to eating oily fish. Especially when the recommendation is to eat 2-3 portions of oily fish a week which seems like an unrealistic demand on current fish stocks. The use of a waste product from the biodiesel industry to grow the organisms on seems a good utilisation of a product which does not have many other uses. The authors commented that the DHA yield was disapointing so I imagine that future research might focus on different species of algae to see if better yields can be achieved.
A Review of;
Ethier S, Woisard K, Vaughan and Wen Z (2011) Continuous culture of the microalgae Schizochytrium limacinum on bio-diesel crude glycerol for producing docosahexaenoic acid. Bioresource Technology. 102: 88-93.
5 comments:
Hi Lee, interesting review!
I imagine this would also be popular amongst vegetarians/vegans that don't like to eat fish products.
It also seems that there is some level of concern over contaminates found in fish products, so I think supplements derived from algae have great potential.
Hi Helen, thanks!
Yes those are two very good points. Both of which the authors discuss actually. We have been learning with Ted Henry about contaminates that accumulate in fish as they move through the food web but the fish are unable to remove them from their tissues. Compounds like methylmercury which enter the environment via industry.
Very good for vegans too.
Sorry, what I ment to say was compounds like mercury enter the marine environment via industry and pesticides and are transformed into methylmercury, mostly by anaerobic microbes.
This sounds like a very interesting and potentially useful idea, did the authors say if the research is continuing and how likely it is that we will be eating algae oils from biofuel waste in the future?
Hi Alice
I think further research in this area is very likely, the authors mention that different species of marine algae should be the main focus to see if more productive species can be identified. Whether or not we will be taking these supplements in the future, it seems a real possibility.
Post a Comment