Kerby C. Jones

Immobilized lipase‐catalysed production of alkyl esters of restaurant grease as biodiesel

Simple alkyl ester derivatives of restaurant grease were prepared using immobilized lipases as biocatalysts. The lipases studied included those of Thermomyces lanuginosa and Candida antarctica supported on granulated silica (gran‐T.l. and gran‐C.a., respectively), C. antarctica supported on a macroporous acrylic resin (SP435) and Pseudomonas cepacia immobilized within a phyllosilicate sol‐gel matrix (IM PS‐30). All alcoholysis reactions were carried out in solvent‐free media employing a one‐step addition of the alcohol to the reaction system. Of the lipases studied, IM PS‐30 was found to be the most effective in catalysing the methanolysis and ethanolysis of grease. The processes catalysed by gran‐T.l. and gran‐C.a. lipases gave poor conversions to esters, and the SP435‐catalysed reactions gave intermediate yields of ethyl and methyl esters. Water activity (aw) was an important factor in the methanolysis reactions; reaction media with aw<0.5 resulted in the highest conversions to methyl esters. Molecular sieves also improved methyl ester yields by as much as 20% in transesterification reactions catalysed by IM PS‐30. The immobilized lipases also were evaluated for their ability to produce alkyl esters of grease with several additional normal and branched‐chain alcohols.

Selectivity of lipases: isolation of fatty acids from castor, coriander, and meadowfoam oils

The lipase-catalyzed hydrolysis of castor, coriander, and meadowfoam oils was studied in a two-phase water/oil system. The lipases from Candida rugosa and Pseudomonas cepacia released all fatty acids from the triglycerides randomly, with the exception of castor oil. In the latter case, the P. cepacia lipase discriminated against ricinoleic acid. The lipase from Geotrichum candidum discriminated against unsaturated acids having the double bond located at the Δ-6 (petroselinic acid in coriander oil) and Δ-5 (meadowfoam oil) position or with a hydroxy substituent (ricinoleic acid). The expression of the selectivities of the G. candidum lipase was most pronounced in lipase-catalyzed esterification reactions, which was exploited as part of a two-step process to prepare highly concentrated fractions of the acids. In the first step the oils were hydrolyzed to their respective free fatty acids, in the second step a selective lipase was used to catalyze esterification of the acids with 1-butanol. This resulted in an enrichment of the targeted acids to approximately 95—98% in the unesterified acid fractions compared to the 70—90% content in the starting acid fractions.

A-ring oxidation products from γ-irradiation of cholesterol in liposomes

Abstractγ-Irradiation of cholesterol in multilamellar vesicles (MLV) at 0–4°C causes oxidation of the A-ring. Two A-ring oxides formed in considerable amounts are cholest-4-en-3-one (10) and cholest-4-ene-3,6-dione (12) in addition to the usual B-ring oxides. Lesser amounts of cholesta-4,6-dien-3-one (11) are also generated. Compounds 10 and 12 were detected and measured in cholesterol irradiated at less than 0.5 kGy in liposomes containing saturated or unsaturated phospholipids. Lesser amounts of 10 and 12, as well as lesser amounts of other cholesterol oxides, were formed when a major constituent of the MLV was dilinoleoylphosphatidylcholine. Autoxidation of cholesterol in MLV also gave rise to small amounts of 10, 11 and 12.

Gamma-irradiation of individual cholesterol oxidation products

Cholesterol and seven of its oxidation products in aqueous suspensions of multilamellar vesicles or sonicated aqueous suspensions were subjected individually to γ-radiation (10 KGy) at 0–4°C in air, N2 or N2O. All compounds underwent some changes under the influence of radiation. β-Epoxide (cholesterol 5β,6β-epoxide) and, to a much lesser extent, α-epoxide (cholesterol 5α,6α-epoxide) were converted in low yield to 6-ketocholestanol (5α-cholestan-3β-ol-6-one). 7β-Hydroxycholesterol (cholest-5-ene-3β,7β-diol) and, to a lesser extent, 7α-hydroxycholesterol (cholest-5-ene-3β,7α-diol) gave low yields of 7-ketocholestanol (5α-cholestan-3β-ol-7-one). The latter compound also was obtained by irradiation of 7-ketocholesterol (cholest-5-ene-3β-ol-7-one). 6-Ketocholestanol and 7-ketocholestanol are potential biomarkers for irradiated meat and poultry.

Separation of Structured Lipids by High Performance Liquid Chromatography

SummaryMedium-chain triacylglycerols (TAG) [tributyrin (1,2,3-tributyrylglycerol), tricaproin (1,2,3-tricaproylglycerol), and tricaprylin (1,2,3-tricapryloylglycerol)] were subjected to acidolysis with stearic acid or interesterified with hydrogenated soybean oil (HSO) using an immobilized lipase as catalyst for the synthesis of structured lipids (SL.). Normal phase (silica or cyanopropyl phases; NPSIL or NPCN, respectively) and reverse phase (octadecylsilane, RPODS) high performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD) were used to separate the newly synthesized SL. The NP-HPLC methods fully resolved SL-TAG isomers containing butyryl (C4) and long-chain fatty acyl [stearoyl (C18) and palmitoyl (C16)] residues, but SL-TAG isomers composed of caproyl (C6) or capryloyl residues (C8) and long-chain fatty acyl residues were not fully resolved. The latter SL-TAG molecules were resolved using the RP-HPLC method. The HPLC methods were combined with mass spectrometric detection (LC-MS) to characterize the SL molecular species produced.

Phyllosilicate sol-gel immobilized lipases for the formation of partial acylglycerides**

Lipase PS-30 (pseudomonas cepacia) and Lipase F (Rhizopus oryzae), immobilized within a phyllosilicate sol-gel matrix, catalyzed the esterification of glycerol with short, medium and long-chain fatty acids to produce mono (MAG), di (DAG) and tri (TAG) acylglycerols. The results from the above esterification reactions were compared to reactions using a commercially available immobilized lipase, Lipozyme IM-60. Time course studies showed that free Lipase PS-30 or Lipase F enhanced esterification reactions with the use of silica-supported glycerol. In contrast, immobilized Lipase PS-30-catalyzed reactions occurred at the same conversion rate when using either free or silica-supported glycerol. For immobilized Lipase F and Lipozyme IM-60 reactions, the use of silica-supported glycerol favored the production of DAG and TAG over MAG. All three immobilized lipases could be reused for acylglycerol production.

Immobilized lipoxygenase in a packed-bed column bioreactor: continuous oxygenation of linoleic acid1

The continuous oxygenation of linoleic acid (LA) by immobilized lipoxygenase (LOX) was studied. Enzymatic oxidation was carried out in a recirculating packed column reactor using immobilized LOX as the stationary phase and LA as the substrate. The column, when packed with LOX immobilized in either a calcium alginate sol‐gel matrix or a phyllosilicate sol‐gel matrix, is equivalent to five continuous stirred tank reactors (CSTRs). The reactor cascade was calculated from the residence‐time distribution for the reactor. Based on mass‐balance calculations, a set of mathematical equations for predicting the concentration of oxygenated product generated in each CSTR was calculated. Product formation in the packed column reactor was simulated and results calculated with the model were compared with the experimental results. The data indicated that product yield (hydroperoxyoctadecadienoic acid, HPOD) increased asymptotically with reaction time. Experimentally, when the bioreactor was packed with calcium alginate sol‐gel‐immobilized LOX, an initial linear increase in HPOD production with time was observed, but reached a steady state. For the bioreactor packed with phyllosilicate sol‐gel‐immobilized LOX, initial HPOD production increased more rapidly but reached a lower steady‐state concentration. From these data, a simple computer simulation model was developed to determine the process kinetics of this reactor design.

Compositional Analyses and Shelf‐Life Modeling of Njangsa (Ricinodendron heudelotii) Seed Oil Using the Weibull Hazard Analysis

This study investigated the compositional characteristics and shelf-life of Njangsa seed oil (NSO). Oil from Njangsa had a high polyunsaturated fatty acid (PUFA) content of which alpha eleostearic acid (α-ESA), an unusual conjugated linoleic acid was the most prevalent (about 52%). Linoleic acid was also present in appreciable amounts (approximately 34%). Our investigations also indicated that the acid-catalyzed transesterification of NSO resulted in lower yields of α-ESA methyl esters, due to isomerization, a phenomenon which was not observed under basic conditions. The triacylglycerol (TAG) profile analysis showed the presence of at least 1 α-ESA fatty acid chain in more than 95% of the oils TAGs. Shelf-life was determined by the Weibull Hazard Sensory Method, where the end of shelf-life was defined as the time at which 50% of panelists found the flavor of NSO to be unacceptable. This was determined as 21 wk. Our findings therefore support the potential commercial viability of NSO as an important source of physiologically beneficial PUFAs.