Front Matter

and Kazlauskas, 1999). They offer TG concentrates of EPA and DHA of a whole

range of composition including 100 % EPA or DHA, of high purity, highly effi-

ciently, and in excellent yields. Neither chemicals nor organic solvents are re-

quired; thus these processes are highly feasible from industrialization as well as

environmental hazard points of view. Nowadays, numerous industrial companies

in the field are realizing the advantages and potential offered by the lipases, and

some of them have marketed – or are about to market – TG concentrates of EPA

and DHA. It is interesting to know that the Japanese authorities have not allowed

concentrated ethyl esters or chemically modified n-3 concentrates to be sold as health

food, only concentrated TG produced by lipases having been allowed forgeneral sale.

Lipases can also be employed to enrich various other lipid classes with n-3 fatty

acids, including PL and ether lipids (EL) of the 1-O-alkyl-2,3-diacyl-sn-glycerol

type, which are characteristic of the fat in shark liver oil. PL highly enriched

with EPA and DHA of the type occurring in fish are highly interesting and will

certainly offer many interesting possibilities to the food supplement and pharmaceu-

tical field. There is no doubt that there will soon be a strong demand for such PL.

Lipases can also be used to provide such lipids that are structurally labeled with EPA

and/or DHA into thesn-2 orsn-3 positions of PL or EL.

Lipases have also found applicability in concentrating EPA and DHA in fish oils.

This application is based on their fatty acid selectivity, which can be utilized in

concentrating EPA and DHA by kinetic resolution. Concentration levels of 50–

70 % EPA+DHA can easily be obtained in high recovery directly from fish oil

by lipase-catalyzed hydrolysis or alcoholysis reactions. Higher levels are obtained

with free acids or monoesters, and separation of EPA and DHA is also offered by

lipases which discriminate between EPA and DHA. Enrichment levels above 90 %

can be obtained in two-step enzyme processes in high recoveries, and it is anticipated

that lipases may be used to purify EPA and DHA toward high purity levels. This is

also highly important from an industrialization point of view, as some of these pro-

cesses do not require solvents or chemicals.

Currently, much research effort is being placed on the application of lipases for

producing positionally labeled or structured lipids. Again, this is based on lipase

selectivity, but in this case by their regioselectivity towards their natural acylglycer-

ol substrates. 1,3-Regioselective lipases are lipases that act with a high preference or

exclusively at the primary alcoholic end-positions of the TG, and have found an

enormous use in this field. This is of great importance in the n-3 field, and TG en-

riched with EPA or DHA in thesn-2 position or thesn-1 andsn-3 positions will be

offered for clinical and nutritional purposes. The potential in this field is clearly very

high.

A different type of structured lipids, enantiostructured TG, may also find interest

in the future. Their production is based on lipase enantioselectivity towards either the

sn-1 or thesn-3 position of TG. Reports already exist in the literature of lipases

displaying this type of selectivity towards TG (Villeneuve et al., 1995; Chandler

et al., 1998), but this needs to be amplified further to offer some realistic advantages

in the near future. There is little doubt that the resulting chiral structured lipids may

offer various interesting aspects to the n-3 lipid field.

Finally, lipases can be employed to provide chiral precursors of glycerol deriva-

tives as building blocks for asymmetric synthesis of the more complex PL and EL,

172 10 Enrichment of Lipids with EPA and DHA by Lipase