Comparative fatty acid selectivity of lipases in esterification reactions with glycerol and diol analogues in organic media

Characteristics and emulsifying properties of structured phospholipids from palm pressed fiber and omega-3 fatty acid concentrates from by-products of fish processing by enzymatic acidolysis

The synthesis of structured phospholipids (SPLs) containing ω-3 fatty acids was carried out through enzymatic acidolysis reactions using lipase from Rhizomucor miehei between palm pressed fiber phospholipids (PPF PL) with four ω-3 fatty acid concentrates as different acyl sources. The purity of SPLs increased compared to original PPF PLs. The degree of ω-3 fatty acid incorporation to the SPLs was different that depended on the sources of acyl. The highest degree of incorporation was in PE (phosphatidylethanolamine). The phenomenon of acyl migration of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) was found from the sn-1 to the sn-2 position of the PE. This acyl migration occurred at all four SPLs. Modification of PLs made better emulsifying properties for oil in water emulsion system, compared to PPF PL. The increase in the HLB (hydrophilic-lipophilic balance) value, EAI (emulsifying activity index), and ESI (emulsion stability index) of SPLs compared to PPF PL was supposed to relate to an increase in polarity. The composition of more polar PLs (PC/phosphatidylcholine, PE, PG/phosphatidylglycerol, and PA/phosphatidic acid) in the four SPLs is higher than that of PPF PL. The sources of acyl also affected the emulsifying properties of four SPLs.

A multisubstrate assay for lipases/esterases: assessing acyl chain length selectivity by reverse-phase high-performance liquid chromatography

Lipases and esterases are hydrolytic enzymes and are known to hydrolyze esters with unique substrate specificity and acyl chain length selectivity. We have developed a simple competitive multiple substrate assay for determination of acyl chain length selectivity of lipases/esterases using RP-HPLC with UV detection. A method for separation and quantification of 4-nitrophenyl fatty acid esters (C4-C18) was developed and validated. The chain length selectivity of five lipases and two esterases was determined in a multisubstrate reaction system containing equimolar concentrations of 4-nitrophenyl esters (C4-C18). This assay is simple, reproducible, and a useful tool for determining chain length selectivity of lipases/esterases.

Lipase specificity towards eicosapentaenoic acid and docosahexaenoic acid depends on substrate structure

The fatty acid specificity of five lipases towards eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was evaluated in the hydrolysis of fish oil, squid oil and a model system. The model system contained methyl esters of EPA, DHA and palmitic acid. All the investigated lipases discriminated against both EPA and DHA more in the model system than in the natural oils. Thus both EPA and DHA were more easily hydrolysed from a glyceride than from a methyl ester. In the model system, the lipase from Candida rugosa showed the highest discrimination against DHA, while the lipases from Pseudomonas fluorescens and Pseudomonas cepacia discriminated against EPA the most. In a glyceride, the fatty acid specificity of lipases towards EPA and DHA was affected by the positional distribution of the fatty acids and the glyceride structure due to the regiospecificity and triglyceride specificity of the lipase. In the oils, the Pseudomonas lipases also discriminated against EPA the most, while DHA was initially discriminated the most by the lipase from Thermomyces lanuginosus. However, after longer reaction times the enrichment of DHA in the glyceride fraction of the oils was greatest for the lipase from C. rugosa.

Effect of water activity and immobilization on fatty acid selectivity for esterification reactions mediated by lipases

The effect of water activity (a(w)) and immobilization on fatty acid (FA) selectivity of Burkholderia (formerly Pseudomonas) cepacia, Rhizomucor miehei, Candida antarctica (type B), and Candida rugosa lipases in esterification reactions was determined. Studies were based on measuring ester formation in multicompetitive reaction mixtures containing either the homologous series of even carbon number n-chain saturated FA (C4-C18) or a series of n-chain (un)saturated FA (C18:X, where X = 0-3 double bonds) as cosubstrates with 1,3-propanediol in ter-butyl methyl ether at a(w) of 0.19, 0.69, and 0.90. Activity and FA selectively patterns were similar for free and Celite-adsorbed lipases in response to changes in a(w'), although specific effects were observed for selectivity of B. cepacia and C. rugosa lipases toward C16 and C4/C6 FA, respectively. Also, selectivity toward unsaturated C18:X FA as a group was modulated by changes in a(w) for three of the four lipase studied. Resin-fixed lipases from R. miehei and C. antarctica exhibited profound differences in activity and FA selectively in response to changes in a(w'), relative to free and Celite-bound forms. These findings suggest that FA selectivity for lipid modification is influenced by a(w) and immobilization, but that each lipase has a characteristic response to these factors in a manner that cannot be predicted.