Sex pheromone communication in the nematode,Rhabditis pellio

Both males and females ofRhabditis pellio release pheromones that attract the opposite sex prior to copulation. A quantitative bioassay for the female-produced pheromone was designed, based on male movement toward a pheromone source placed at one end of a 10-mm strip of bacterial material maintained on nutrient agar in a petri plate. Females produced pheromone from the age at which they attained the adult stage (3 days following hatching from the egg) and maintained a relatively constant production level until at least the ninth day of life. Similarly, males became responsive to the female pheromone by the third day and remained responsive through the ninth day, although the time required for the males to migrate toward a female pheromone source increased with increasing age. No daily rhythm of pheromone responsiveness by males or pheromone production by females was observed when the nematodes were conditioned to a 1212 h light-dark cycle.     

Variation in fatty acid content and seed weight in some lauric acid richCuphea species

Significant genetic variation for lauric acid (12∶0) and capric acid (10∶0) composition and seed weight was measured within lauric acid-rich, self-pollinating germplasm accessions ofCuphea wrightii, C. tolucana, andC. lutea. Means and ranges of individual plant progenies for 12∶0 content ofC. wrightii accessions was 60.5±.63% (49.8±65.8%), 10∶0 content was 23.7±.54% (18.6±33.0%), and 1000-seed weight was 1.50±.03 g (1.20–2.47 g). Progenies of single plant selections carried to the S₂ generation exhibited reduced variability within selections, but significant variation among selections for 12∶0, 10∶0 and 1000-seed weight. Variation among single plant selections ofC. tolucana was less than that ofC. wrightii and attributed to a restricted germplasm base. Means and ranges for 12∶0 content were 61.6±.47% (59.2–69.9%), 10∶0 was 22.3±.62% (11.7–25.3%), and 1000-seed weight was 1.40±.05 g (0.90–1.69 g).Cuphea lutea has a significantly different 12∶0−10∶0 profile than the other lauric acid-rich species. Means and ranges for 12∶0 were 36.8±.14% (33.7–40.8%), 10∶0 was 21.8±.08% (16.4–23.9%), 1000-seed weight was 2.26±.02 g (1.82–272 g). The 1000-seed weight was highly positively correlated with 8∶0, 10∶0, 18∶1 and 18∶2 contents and highly negatively correlated with 12∶0, 14∶0 and 16∶0 in bothC. wrightii andC. tolucana. No such relationship was found forC. lutea. A highly significant negative correlation was also measured for 12∶0 and 10∶0 contents inC. wrightii andC. tolucana.     

Calling behavior and pheromone titer in the smaller tea tortrix moth,Adoxophyes sp. (Lepidoptera: Tortricidae)

The calling behavior and pheromone titer in the female smaller tea tortrix moth,Adoxophyes sp., were investigated under a 1410-hr light-dark photoperiod. Quantitative gas chromatographic analysis of ovipositor extract for (Z)-11-tetradecenyl acetate (Z11–14Ac) and (Z)-9-tetradecenyl acetate (Z9–14Ac), the major pheromone components of this species, obtained on the third day postemergence, indicated that extractable amounts of sex pheromone were present throughout the period of observation. Maximal pheromone titer and calling activity was reached at 8 and 10 hr after onset of scotophase, respectively. The ratio ofZ11–14Ac toZ9–14Ac through the 24-hr period varied significantly. The significance of the sex pheromone component ratio variation on the attraction of males was tested in a field experiment. The ratio of males trapped by the most attractive blend versus the least attractive one was 2.16.     

Lipase-catalyzed acidolysis of tristearin with oleic or caprylic acids to produce structured lipids

Two different structured lipids (SL) were synthesized by transesterifying tristearin with caprylic acid (C8∶0) or oleic acid (C18∶1). The objective was to synthesize SL containing stearic acid (C18∶0) at the sn-2 position as possible nutritional and low-calorie fats. The reaction was catalyzed by IM60 lipase from Rhizomucor miehei in the presence of n-hexane. The effects of reaction parameters affecting the incorporation of caprylic acid into tristearin were compared with those for incorporating oleic acid into tristearin. For all parameters studied, oleic acid incorporation was higher than caprylic acid. The range of conditions favorable for synthesizing high yields of C8∶0-containing SL was narrower than for oleic acid. An incubation time of 12–24 h and an enzyme content of 5% (w/w total substrates) favored C8∶0 incorporation. The mole percentage of incorporated C18∶1 did not increase further at enzyme additions greater than 10%. C18∶1 incorporation decreased with the addition of more than 10% water (w/w total substrates) to the tristearin-oleic acid reaction mixture. Increasing the mole ratio of fatty acid (FA) to triacylglycerol increased oleic acid incorporation. The highest C8∶0 incorporation was obtained at a 1∶6 mole ratio of tristearin to FA. Positional analysis confirmed that C18∶0 remained at the sn-2 position of the synthesized SL. The melting profiles of tristearin-caprylic acid and tristearin-oleic acid SL displayed peaks between −20 to 30°C and −20 to 40°C, respectively. Their solid fat contents (∼25%) at 25°C suggest possible use in spreads or for inclusion with other fats in specialized blends.     

Molecular architecture and biophysical properties of phospholipids during thermal adaptation in fish: An experimental and model study

Phospholipids from livers of carps (Cyprinus carpio L.) adapted to winter (5°C) and summer (25°C) temperatures were isolated, and the fatty acid composition of total phospholipids, as well as molecular species composition of diacyl phosphatidylcholines and ethanolamines, were determined. Order parameter of 5-doxyl stearic acid and steady-state fluorescence anisotropy of different anthroyloxy fatty acids—[2-, 12(N-9-anthroyloxy)stearic acid and 16(N-9-anthroyloxy)palmitic acid—embedded in native and synthetic (16∶0/16∶0, 16∶0/22∶6, 18∶0/22∶6, 18∶1/22∶6, 20∶4/20∶4, 22∶6/22∶6 phosphatidylcholines and 16∶0/18∶1, 18∶1/22∶6 phosphatidylethanolamines) phospholipid vesicles was also determined between −30 and 30°C and 5 and 30°C, respectively. There is an accumulation of 1-monoenoic, 2-polyenoic diacyl phosphatidylcholine and ethanolamine with a concomitant reduction of 1-stearoyl,2-docosahexaenoyl species in the cold-adapted state. Despite a 30% accumulation of long-chain polyunsaturated fatty acids in phospholipids in cold, there is only a 5°C downshift in the solid-gel to liquid-crystalline phase transition temperature (−8 vs. −13°C). Vesicles from total phospholipids of cold-adapted fish proved to be more disordered in all segments than from the warmadapted ones when assayed using 2,12-(N-9-anthroyloxy)stearic and 16-(N-9-anthroyloxy)palmitic acid. Vesicles made from purified phosphatidylcholines showed the same pattern, but they were more disordered than the corresponding total phospholipids. This could be modelled using mixed phospholipid vesicles made of synthetic 16∶0/22∶6 phosphatidylcholine (75%) and either 18∶1/22∶6 phosphatidylethanolamine (25%) vs. 16∶0/18∶1 phosphatidylethanolamine (25%) and comparison of the anisotropy parameters of 100% 16∶0/22∶6 and 100% 18∶1/22∶6 phosphatidylcholine vesicles. Mixing either 16∶0/18∶1 (25%) or 18∶1/22∶6 (25%) phosphatidylethanolamines to 18∶0/22∶6 (75%) phosphatidylcholine shifted down or up, respectively, the transition temperature of vesicles compared to 100% 18∶0/22∶6 vesicles assayed by electron spin resonance spectroscopy using 5-doxylstearic acid. It is concluded that it is not the gross amount of long-chain polyunsaturated fatty acids in phospholipids, but rather their specific combination withcis Δ9 monounsaturated fatty acids in the positionsn-1, especially in phosphatidylethanolamines, that is important in determining the physical properties of biomembranes in relation to adaptational temperature.     

Plackett-burman design for determining the preference of Rhizomucor miehei lipase for FA in acidolysis reactions with coconut oil

The preference of lipase (EC 3.1.1.3) from Rhizomucor miehei in the incorporation of 11 FA, ranging from C10∶0 to C22∶6, into coconut oil TAG during acidolysis was studied by applying the Plackett-Burman experimental design. Enzymatic acidolysis reactions were carried out in hexane at 37°C for 48 h with coconut oil (0.1 M) and a mixture of 11 FA at a TAG to FA molar ratio of 1∶1. Lipase was used at the 5 wt% level. The incorporation of FA into coconut oil TAG was determined by GC. The lipase showed preference for long-chain saturated FA for incorporation into coconut oil TAG. The FA with 18 carbon atoms showed a high incorporation rate (18∶1>18∶1>18∶3). The lipase showed the least preference for the incorporation of 12∶0, which occurs in maximal concentration (46%), whereas the most preferred FA, 18∶0, occurs at a very low concentration (<2%) in coconut oil. The overall preference of lipase for the incorporation of different FA into coconut oil TAG was 18∶0>18∶2, 22∶0>18∶1, 18∶3, 14∶0, 20∶4, 22∶6>16∶0>12∶0≫10∶0.     

Individual variation in sex pheromone of smaller tea tortrix moth,Adoxophyes sp. (Lepidoptera: Tortricidae)

Female smaller tea tortrix mothsAdoxophyes sp. (Lepidoptera: Tortricidae), which initiated calling at 1, 2, or 3 days old, respectively, were analyzed individually for (Z)-11-tetradecenyl acetate (Z11-14:OAc) and (Z)-9-tetradecenyl acetate (Z9–14: OAc) in the pheromone gland via GLC. Among different age groups, broad and similar distributions were found for pheromone quantity (¯X=58.6±52.9 ng/female; range 1.3–219.8 ng/female). The ratio of the two pheromone components averaged 6535 but ranged from 8416 to 4060. The significance of the pheromone blend variation to the attraction of males was tested in a field experiment. The ratio of males trapped by the most attractive blend versus the least attractive one was 2.2.     

Biology of pheromone release by male caribbean fruit flies,Anastrepha suspensa (Diptera: Tephritidae)

Males of the Caribbean fruit fly,Anastrepha suspensa (Loew), typically form leks and attract females by releasing a multicomponent volatile pheromone. Previous reports have identified two nine-carbon alcohols, three lactones, a sesquiterpene, and a monoterpene in the volatiles. The present report is a study of the physiology of male pheromone release and of ecological and social interactions that influence pheromone release by laboratoryreared flies. Volatiles released by males were trapped on Tenax, eluted, separated, and quantitatively measured by gas chromatography. Experiments showed that the volatiles were primarily released from mouth and anus. Sealing the anal opening or the mouth with melted beeswax resulted in up to 40% or greater reduction in most components, and sealing both mouth and anus further reduced release of volatiles, but some volatiles are possibly still released directly from the cuticle. An anal pouch of everted tissue played a major role as a large evaporative surface for release of some of the volatile components. Male flies entrained to a 1410 light-dark cycle showed a peak release of volatiles at 11–12 hr into the photophase, but smaller quantities of the same volatiles were released over a broad period during the daylight hours. Laboratory-reared males peaked in pheromone release at 7–10 days and production and release continued through 35 days of age. Single males released significantly more of all components measured than did groups of males. The reduction by aggregations of males may be related to lekking behavior in this fruit fly. The pheromone probably serves to attract females to a lek site, but additional parameters are likely to enter into the choice of male made by the arriving female.This is University of Florida Agricultural Experiment Station Journal Series No. 9589.     

Molecular species composition of phosphatidylcholine fromCrypthecodinium cohnii in relation to growth temperature

The molecular species composition was determined for phosphatidylcholine (PC) isolated from the marine dinoflagellateCrypthecodinium cohnii grown at three different temperatures. At all three temperatures the didocosahexaenoyl species comprised about 25% of the PC with 14∶0/22∶6 and 16∶0/22∶6 also being of major importance; these three species comprised 75–82% of the total. Another 20 species were identified, including several short chain disaturated species. Only small differences in the composition of PC were found in response to growth at 16, 23 and 27°C. On dropping the growth temperature from 27°C to 16°C the largest changes were a decrease of 8.9% in saturated/saturated species and an increase of 5.3% in saturated/PUFA species; the 22∶6/22∶6 content only increased slightly (by 1.9% to 25.4%). This unusual molecular species composition is discussed.     

Influence of temperature and high dietary linoleic acid content on esterification,elongation, and desaturation of PUFA in atlantic salmon hepatocytes

The esterification, desaturation, and elongation of [1-¹⁴C]18∶3n−3, [1-¹⁴C]18∶2n−6, and [1-¹⁴C]20∶5n−3 at 5 and at 12°C were studied using cultivated hepatocytes from Atlantic salmon. The salmon were fed diets, in which 0, 50, or 100% of the supplementary fish oil had been replaced by soybean oil, for 950 day-degrees at 5 and 12°C. The endogenous percentage of 18∶2n−6 in hepatocyte lipids was 2% in cells from fish fed a diet with 100% of the supplemental lipid from fish oil, and it was slightly less than 25% in cells from fish fed the diet with 100% of the supplemental lipid from soybean oil. Furthermore, the percentages of 20∶3n−6 and 20∶4n−6 were significantly higher in hepatocytes from fish fed on soybean oil than they were in those of fish fed on fish oil. The percentages of 20∶5n−3 and 22∶6n−3, on the other hand, were lower. The endogenous levels of n−6 FA were not significantly correlated with the total amounts of radiolabeled FA esterified in hepatocyte lipids. The main radiolabeled products formed from 18∶2n−6 were 20∶2n−6 and 20∶3n−6. The level of the important eicosanoid precursor 20∶4n−6 was twice as high in hepatocyte phospholipids from fish fed the 100% soybean oil diet as it was in hepatocytes from fish fed the diet with 100% of supplemental lipid from fish oil. The main products formed from 18∶3n−3 were 20∶4n−3, 20∶5n−3, and 22∶6n−3. High levels of dietary 18∶2n−6 do allow, or even seem to increase, the production of 22∶6n−3 from 18∶3n−3 in hepatocytes. The main products formed from 20∶5n−3 were 22∶5n−3 and 22∶6n−3. The production of 22∶6n−3 from 20∶5n−3 was higher at 5°C than at 12°C. The percentage of 24∶5n−3 was higher at 5°C than it was at 12°C, as was the ratio of 24∶5 to 22∶5. These results suggest that the elongation rate of 22∶5n−3 to 24∶5n−3 is higher at the lower temperature.     

Enzymatic preparation of enantiomerically pure sn-2,3-diacylglycerols: A stereoselective ethanolysis approach

Stereoselective ethanolysis of monoacid TAG by immobilized Rhizomucor miehei lipase (RML) was studied for preparation of optically pure sn-2,3-DAG. Trioctanoylglycerol (TO) was used as a model substrate. The enantiomeric purity of the product, sn-2,3-dioctanoylglycerol (sn-2,3-DO), was very high (percent enantiomeric excess >99%) when an excess of ethanol was used. The result indicated that RML was highly stereoselective toward the sn-1 position of TO under conditions of excess ethanol. The stereoselectivity of RML depended on the amount of ethanol. The larger the amount of ethanol was, the higher the stereoselectivity became. After optimizing the parameters such as reactant molar ratio, water content, and temperature, (ethanol/TO molar ratio =31∶1 and water content =7.5 wt% of the reactants at 25°C), optically pure sn-2,3-DO was obtained at 61.1 mol% in the glyceride fraction in 20 min. The above conditions were further applied for ethanolysis of monoacid TAG with different acyl groups such as tridecanoylglycerol (C10∶0), tridodecanoylglycerol (C12∶0), tritetradecanoylglycerol (C14∶0) and trioctadecenoylglycerol [triolein, (C18∶1)]. The yields and enantiomeric purities of 1,2(2,3)-DAG were dramatically reduced when TAG with FA longer than decanoic acid were used.     

Effect of Female Age on Daily Cycle of Sexual Pheromone Emission in Gregarious Egg Parasitoid Anaphes listronoti

The temporal pattern of pheromone emission by Anaphes listronoti females was established in a four-arm olfactometer by observing, at 2-hr intervals, the response of <2-hr-old males to odor produced by individual virgin females of <1, 1, and 2 days of age. This is the first evidence of a sexual pheromone in a Mymaridae. Under a 16L:8D photoperiod and 24°C constant temperature, the responsiveness of males to females of different ages varied significantly during the photophase. When <1-day-old females were used, males made significantly more final choices in the pheromone field than odorless fields at 4 and 6 hr after the onset of the photophase, and their walking speed was significantly higher from 4 to 12 hr, suggesting that females began to release a long-range pheromone during this period. Final choices and high walking speed were observed earlier with 1- and 2-day-old females than with <1-day-old females, and there was a significant decrease in male responses at 6 hr after the onset of the photophase, suggesting a bimodal temporal pattern of sexual pheromone emission.     

Possible fatty acyl pheromone precursors in Spodoptera littoralis. Search for 11- and 12-hydroxytetradecanoic acids in the pheromone gland

Lipidic extracts of Spodoptera littoralis pheromone glands submitted to acid methanolysis using: (i) sulfuric acid/methanol/benzene (0.1∶4∶2, by vol) at 90°C for 1 h; (ii) 12 N HCl/methanol (1∶2; vol/vol) at 90°C for 1 h, or (iii) 14% BF₃-MeOH at 90°C for 1 h did not reveal the presence of either 11- or 12-hydroxytetradecanoic acid in the extracts, as concluded from the gas chromatography-mass spectrometry analyses. Under the above methanolysis conditions, a synthetic sample of methyl (14, 14, 15-²H₃) 12-hydroxytetradecanoate remained unaltered. These results may indicate that formation of (E)-11-tetradecenoic acid from tetradecanoic acid does not occur in the pheromone gland by dehydration of an intermediate hydroxyacid. Acid methanolysis of a lipidic extract using BF₃-MeOH led to the formation of a mixture of methoxy fatty acid methyl esters, identified by gas chromatography-mass spectrometry. These methoxy derivatives should arise from BF₃-catalyzed addition of methanol to the double bond of the natural monounsaturated fatty acyl derivatives present in the gland. Thus, under the same conditions, a synthetic sample of methyl (Z)-11-tetradecenoate was partially transformed into methyl 11-methoxytetradecanoate and methyl 12-methoxytetradecanoate. This reaction might be a useful alternative procedure to obtain methoxy derivatives of olefins, which are very helpful for the structural characterization of the parent alkenes.     

Effect of apolipoprotein E polymorphism on serum lipoprotein response to saturated fatty acids

This report summarizes two studies which investigated the effects of apolipoprotein E (apoE) polymorphism on the serum total cholesterol (TC) and lipoprotein cholesterol responses to 8∶0+10∶0 and 12∶0 diets (Study I) and 14∶0, 16∶0, and 18∶0 diets (Study II). Eighteen healthy premenopausal women (3 apoE 3/2, 12 apoE 3/3, 3 apoE 4/3) in study I and another 18 healthy premenopausal women (4 apoE 3/2, 10 apoE 3/3, 3 apoE 4/3, 1 apoE 4/2) in study II consumed a baseline diet providing 40 en% total fat, 11 en % 18∶2, 15 en% 18∶1, 11.5 en% saturated fat for the first week of each 5-wk period. The experimental diets for both studies provided 40 3n% total fat, 13–14 en% as one of five test saturated fatty acids (SFA), 14–16 en% 18∶1, and 3–4 en% 18∶2. Analysis by apoE phenotypes showed that both the 8∶0+10∶0 diet and the 12∶0 diet in Study Linduced significant increases in serum TC in subjects with different apoE phenotypes with the exception of apoE 3/2 in the medium-chain triglyceride group. In contrast, in Study II, individuals with apoE 4/3 consuming the 14∶0 diet showed significant increases in serum TC, high density lipoprotein-cholesterol (HDL-C), and HDL2-C, but the same subjects consuming the 16∶0 diet showed significant increases in serum TC and low density lipoprotein-cholesterol. The findings from both studies indicated serum lipoprotein responses to SFA were different and the variation of responsiveness may be regulated, at least in part, by apoE polymorphism, especially when 14∶0, 16∶0, or 18∶0 was consumed.     

Trans-monoenoic and polyunsaturated fatty acids in phospholipids of aVibrio species of bacterium in relation to growth conditions

AVibrio species of bacterium known to contain the polyunsaturated fatty acid 20∶5n−3 was grown in both freshwater and seawater media at 5 and 20°C and examined for adaptive changes in lipid composition. Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), together with a smaller proportion of nonesterified fatty acids (NEFA), comprised almost all the lipid under all growth conditions examined. Temperature had a more pronounced effect than the salinity of the medium on lipid composition. The proportion of PE in total lipid was always higher at 5 than at 20°C. Conversely, the proportion of NEFA was lower at 5 than 20°C whereas that of PG was not altered. The levels of saturated fatty acids in total lipid, PE and PG were all decreased by growth at 5°C. No differences were observed with respect to growth temperature in the levels ofcis 16∶1n−7, the principal monoenoic fatty acid in both PE and PG.Trans 16∶1n−7 was found to comprise 12.8–15.2% of fatty acids in PE and PG of bacteria grown at 5°C but only 4.4–8.5% of phospholipid fatty acids in bacteria cultured at 20°C. Regardless of medium composition, a reduction in growth temperature from 20 to 5°C also caused the proportions of 20∶5n−3 to increase from around 0.8 to 4.4% in PE and from around 4 to 20% in PG. The simultaneous occurrence oftrans 16∶1n−7 and 20∶5n−3 is unique to thisVibrio species of bacterium. The increased proportions of both these fatty acids with decreasing temperature suggest that they have a role in retailoring biomembrane phospholipids during temperature acclimation of the bacterium.     

Effect of temperature on the incorporation into phospholipid classes and metabolismvia desaturation and elongation of n−3 and n−6 polyunsaturated fatty acids in fish cells in culture

The incorporation of 18∶2n−6, 18∶3n−3, 20∶4n−6 and 20∶5n−3 was greater at 10°C than at 22°C in Atlantic salmon (AS), rainbow trout (RTG-2) and turbot (TF) cells. However, there were generally no significant differences between the amount of incorporation of all four polyunsaturated fatty acids (PUFA) into total lipid within a cell type at either 22°C or 10°C. The distributions of the PUFA between individual phospholipid classes at 22°C was essentially the same in AS and TF cells—with the C₁₈ PUFA the order of incorporation in these cells was phosphatidylcholine (PC) > phosphatidylethanolamine (PE) > phosphatidic acid/cardiolipin (PA/CL); with 20∶4n−6 the order was PE and phosphatidylinositol (PI)>PC; with 20∶5n−3, PE>PC. In RTG-2 cells at 22°C the distributions of the C₁₈ PUFA were similar to the other cell lines, but with 20∶4n−6 the order was PC>PI>PE, and with 20∶5n−3 it was PC>PE. At 10°C the incorporation of C₁₈ PUFA into PC increased and into PE and PA/CL decreased, in general, in all cell lines. Incorporation of 20∶5n−3 into PC and PE was increased and decreased at 10°C, respectively, in AS and TF cells, whereas in RTG-2 cells the changes at 10°C were opposite i.e., increased in PE and decreased in PC. With 20∶4n−6, incorporation into PC at 10°C was increased in all cell lines with decreased incorporation into PI in AS and RTG-2 cells and into PE in AS and TF cells, whereas incorporation of 20∶4n−6 into PE increased in RTG-2 cells. The metabolismvia desaturation and elongation of the n−3 PUFA was greater than that of the equivalent n−6 PUFA in all cell lines, irrespective of temperature. There was less conversion of the C₁₈ PUFA at 10°C than at 22°C in RTG-2 and TF cells, but the conversion of 18∶3n−3 by AS cells was increased at 10°C. Temperature had no effect on the conversion of the C₂₀ PUFA.     

Reaction selectivity of <Emphasis Type="Italic">Burkholderia cepacia</Emphasis> (PS-30) lipase as influenced by monoacylation of <Emphasis Type="Italic">sn</Emphasis>-glycerol

Reaction selectivities were determined in multicompetitive reactions mediated by Burkholderia cepacia lipase (Amano PS-30) at a water activity of 0.19 in hexane. Saturated FA (C4–C18 even chain) and oleic acid (C18∶1) were reacted with a single alcohol, glycerol, α-or β-MAG, containing C4, C10, C16, or C18∶1 individually as alcohol cosubstrate. Similar odrinal patterns of FA selectivity, with C8, C10, and C16 preferred over others, were generally observed for incorporation of FA into specific acylglycerol (AG) pools of the 24 specific cases evaluated. The three exceptions were enrichment of C14 and C18 in the MAG pool with α-C16-MAG, substrate, and a general suppression of >C8 incorporation into the TAG pool for reactions with α-C10- and α-C16-MAG. PS-30 lipase selectivity toward MAG was in descending order: α/β-C4-MAG>β-C10-MAG>β-C16-MAG>α/β-C18∶1-MAG>α-C10-MAG>α-C16-MAG. Selectivity in channeling CX of the original CX-MAG substrates into higher AG species was in descending order: α-C10-MAG∼α-C16-MAG>α-C18∶1-MAG>β-C10-MAG∼β-C16-MAG∼β-C18∶1-MAG >α/β-C4-MAG. Generally, MAG were better acyl donors than FA for esterification reactions leading to DAG formation. These observations are relevant to the design of biocatalytic processes intended to yield specifically structured TAG.     

Reaction selectivity of <Emphasis Type="Italic">rhizomucor miehei</Emphasis> lipase as influenced by monoacylation of <Emphasis Type="Italic">sn</Emphasis>-glycerol

Reaction selectivities were determined in multicompetitive reactions mediated by Rhizomucor miehei (RM) lipase at water activity of 0.19 in hexane. Saturated FA (C4–C18 even chain) and oleic acid (C18∶1) were reacted with a single alcohol, glycerol, or α-or β-MAG containing C4, C10, C16, or C18∶1 individually as alcohol cosubstrate. Similar patterns of broad FA selectivity toward C8–C18 FA were generally observed for esterification into specific acylglycerol (AG) pools with the different α/β-CX-MAG cosubstrates. Exceptions were enrichment of C18 in the MAG pool with α-C16-MAG substrate, and a general suppression of C4/C6 FA reactivity and a specific discrimination toward >C8 FA incorporation into the TAG pool, both for reactions with α-C10- and α-C16-MAG. RM lipase selectivity toward MAG was in descending order: β-C18∶1-MAG>α/β-C4-MAG∼β-C10-MAG∼β-C16-MAG>α-C18∶1-MAG >α-C10-MAG∼α-C16-MAG. Selectivity in channeling CX of the original CX-MAG substrates into higher AG species was in descending order: α-C10-MAG∼α-C16-MAG>β-C10-MAGβ-C16-MAG>α-C18∶1-MAG>β-C18∶1-MAG∼ α/β-C4-MAG. Aside from their characteristic FA selectivity, Burkholderia cepacia (PS-30) and RM lipases behaved similarly in terms of MAG selectivity as well as a general conservation of FA selectivity throughout the sequential steps of TAG assembly from FA and glycerol for processes designed to yield specifically structured TAG.     

<Emphasis Type="Italic">In situ</Emphasis> alkaline transesterification: An effective method for the production of fatty acid esters from vegetable oils

The production of simple alkyl FA esters by direct alkali-catalyzed in situ transesterification of the acylglycerols (AG) in soybeans was examined. Initial experiments demonstrated that the lipid in commercially produced soy flakes was readily transesterified during agitation at 60°C in sealed containers of alcoholic NaOH. Methyl, ethyl, and isopropyl alcohols readily participated in the reaction, suggesting that the phenomenon is a general one. Statistical experimental design methods and response surface regression analysis were used to optimize reaction conditions, using methanol as alcohol. At 60°C, the highest yields of methyl ester with minimal contamination by FFA and AG were predicted at a molar ratio of methanol/AG/NaOH of 226∶1∶1.6 with an approximately 8-h incubation. An increase in the amount of methanol, coupled with a reduced alkali concentration, also gave high ester yields with low FFA and AG contamination. The reaction also proceeded well at 23°C (room temperature), giving higher predicted ester yields than at 60°C. At room temperature, maximal esterification was predicted at a molar ratio of 543∶1∶2.0 for methanol/AG/NaOH, again in 8 h. Of the lipid in soy flakes, 95% was removed under such conditions. The amount of FAME recovered after in situ transesterification corresponded to 84% of this solubilized lipid. Given the 95% removal of lipid from the soy flakes and an 84% efficiency of conversion of this solubilized lipid to FAME, one calculates an overall transesterification efficiency of 80%. The FAME fraction contained only 0.72% (mass basis) FFA and no AG. Of the glycerol released by transesterification, 93% was located in the alcoholic ester phase and 75 was on the post-transesterification flakes.