Streamlined enzymatic synthesis of human milk fat substitutes

The positional distribution of palmitic acid (PA) in human milk fat substitutes (HMFSs) plays a pivotal role in mimicking the nutritional profile of human milk fat for nourishing non-breastfed infants. This study innovatively introduced a streamlined enzymatic process for preparing HMFSs rich in sn-2 PA using palm stearin, a PA-rich source without the necessity for positional distribution of PA. The initial step involved enhancing the sn-2 PA concentration through enzymatic interesterification using Lipase UM1, which exhibited superior catalytic efficiency than Novozym 435. This process increased the sn-2 PA level from 40.98 % to 64.51 %. Subsequently, acidolysis was employed to reduce PA levels by replacing PA at sn-1,3 positions using sn-1,3-regioselective lipases. The PA content decreased from 60.64 % to 26.73 %, simultaneously raising the relative sn-2 PA concentration to 71.57 %, meeting the benchmarks for HMFSs. This study establishes a robust conceptual framework for the prospective industrial synthesis of HMFSs.

Progress and perspectives of enzymatic preparation of human milk fat substitutes

Human milk fat substitutes (HMFS) with triacylglycerol profiles highly similar to those of human milk fat (HMF) play a crucial role in ensuring the supply in infant nutrition. The synthesis of HMFS as the source of lipids in infant formula has been drawing increasing interest in recent years, since the rate of breastfeeding is getting lower. Due to the mild reaction conditions and the exceptionally high selectivity of enzymes, lipase-mediated HMFS preparation is preferred over chemical catalysis especially for the production of lipids with desired nutritional and functional properties. In this article, recent researches regarding enzymatic production of HMFS are reviewed and specific attention is paid to different enzymatic synthetic route, such as one-step strategy, two-step catalysis and multi-step processes. The key factors influencing enzymatic preparation of HMFS including the specificities of lipase, acyl migration as well as solvent and water activity are presented. This review also highlights the challenges and opportunities for further development of HMFS through enzyme-mediated acylation reactions.

The Enzymatic Preparation of Human Milk Fat Substitute Intermediate Rich in Palmitic Acid at sn-2 Position and Low-Unsaturated Fatty Acids at sn-1(3) Positions from Palm Oil Substrate

The lipid products that consist of structured lipids rich in palmitic acid (16:0) at the sn-2 position of triacylglycerol (TAG) and rich in low-unsaturated fatty acids (FAs) (LUFAs), such as oleic acid; 18:1 and linoleic acid; 18:2 at the sn-1(3) positions, are useful intermediates for manufacturing human milk fat substitute (HMFS), which contains functional lipid components. In this study, the HMFS intermediate (HMFS-IM) was enzymatically prepared from palm oil without using other oil sources. First, the amount of 16:0 at the sn-2 position of TAG substrate was enhanced from 18.9% to more 34.5% via a random esterification reaction using a non-stereospecific lipase, Novozym^® 435, to produce a random-palm substrate. Consequently, 2-monoacylglycerol (2-MAG) rich in 16:0 at the sn-2 position over 88%, together with the FA ethyl ester substrates rich in LUFAs, such as 18:1-Et and 18:2-Et above 93.5% was prepared through ethanolysis reaction using the same lipase from the random-palm substrate and by purification with urea complexation, respectively. As the preferred modified method, a continuous use of the same lipase to these reactions were achieved while reducing the usage of enzyme to half. Finally, an HMFS-IM rich in 16:0 at the sn-2 position more than 60% and LUFA at sn-1(3) positions was prepared using these palm oil-based products, including random-palm, palm-Et, and 2-MAG, via the interesterification reaction using a 1,3-stereospecific lipase, Lipozyme^® RM-IM. Thus, HMFS-IM was successfully prepared by palm oil materials with a 65 wt% usage ratio. The concept described in this study will be useful for HMFS manufacturing from a single natural oil substrate, which is not initially rich in 16:0 at the sn-2 position.

Enzymatic Preparation and Oxidative Stability of Human Milk Fat Substitute Containing Polyunsaturated Fatty Acid Located at sn-2 Position

The development of human milk fat substitutes (HMFSs), rich in palmitic acid (16:0) at the sn-2 position of triacylglycerol (TAG) and rich in unsaturated fatty acids (FAs) (oleic acid, 18:1 and linoleic acid, 18:2) at the sn-1(3) positions, has gained popularity. In this study, HMFSs containing polyunsaturated fatty acids (PUFAs) predominantly at the sn-2 position were prepared, and their oxidation stabilities were compared. First, a non-PUFA-containing HMFS (NP-HMFS) was produced by enzymatic reactions using Novozyme^® 435 and Lipozyme^® RM-IM as the enzymes and lard as the raw material. Second, HMFSs, containing 10 % PUFA at the sn-2 or sn-1(3) position, were individually prepared by enzymatic reactions using lard and fish oil as raw materials. Here, sn-2-PUFA-monoacylglycerol (MAG) was extracted from the reaction solution using a mixture of hexane and ethanol/water (70:30, v/v) to produce high-purity sn-2-PUFA-MAG with 78.1 % yield. For the PUFA-containing HMFS substrates, comparable oxidation stability was confirmed by an auto-oxidation test. Finally, HMFSs containing 10 % or 2 % sn-1,3-18:1-sn-2-PUFA-TAG species were prepared by enzymatic reactions and subsequent physical blending. The oxidative stability of sn-1,3-18:1-sn-2-PUFA-HMFS was two-fold higher than that of 1/2/3-PUFA-HMFS in which each PUFA was located without stereospecific limitations in TAG. The removal of PUFA-TAG molecular species with higher concentrations of unsaturated units had a significant effect. In addition, the oxidation stability increased with the addition of tocopherol as an antioxidant. Thus, the combined use of two strategies, that is, the removal of PUFA-TAG molecular species with high concentrations of unsaturated units and the addition of antioxidants, would provide a PUFA-containing HMFS substrate with high oxidative stability.