Variability of the lipolytic activity in Yarrowia lipolytica and its dependence on environmental conditions

This work was aimed to the evaluation of the variability of lipolytic activity in Yarrowia lipolytica strains, as well as to asses for a selected strain, the response to the changes of physico-chemical variables (such as pH, NaCl and lipid content), in order to obtain predictive models describing their effects on the lipolysis pattern. The strains tested, having different environmental origin, showed different patterns of the free fatty acids (FFA) released. The clustering of the free fatty acids profiles evidenced that the unweighted average distance within the strains of the same species did not exceeded 30%. However, the lipolytic activity of some strains generated FFA profiles that differentiated from the majority of the strains considered. Also, when a single strain was inoculated in model systems in which pH, NaCl and milk fat were modulated according to a Central Composite Design (CCD), chemico-physical characteristics of the system led to marked variations in the lipolytic activity with consequent changes in individual fatty acids released. In most cases, when the same Y. lipolytica strain was used, under the experimental conditions adopted, the modulation of the lactic acid, NaCl and lipid content did not generate differences in the fatty acid release exceeding 20-21%. However, some combinations of factors remarkably affected lipase expression or activity, and generated differences in the fatty acid released higher than those observed among different strains of the same species.     

The effects of environmental conditions on the lipolytic activity of strains of Penicillium roqueforti

The lipolytic activity of 30 strains of Penicillium roqueforti was investigated by agar diffusion tests on tributyrin (esterase activity) and olive oil agar (lipase activity), by titration of the free fatty acids (FFA) produced and by gas chromatographic analysis of the individual FFA released after growth at 25 or 10 degrees C in butterfat emulsions containing 0, 2 or 7% NaCl. All strains investigated by the agar diffusion tests possessed esterase activity and 23 strains were also able to hydrolyse olive oil, but differences in esterase activity were seen. The agar diffusion tests and the titration of FFA showed that the amount of FFA released by a strain of P. roqueforti is determined by both esterase and lipase activity. A large release of FFA was only seen for strains with the ability to hydrolyse both short- and long-chained fatty acids, while strains with esterase activity produced smaller amounts of FFA. Between 7 and 14 days of incubation a steep increase in the release of FFA was observed both by the titration and by GC analysis, and then a decline from 14 to 21 days, probably caused by conversion of FFA to methyl ketones. Identical FFA profiles were found for two strains with different lipolytic activity. Long-chained fatty acids dominated the profile, while the short-chained fatty acids only were detected in small amounts and mainly in the end of incubation. Both strains were stimulated by NaCl in the emulsions.     

Increase on free fatty acids during ripening of anchovies (Engraulis anchoíta)

The changes of free fatty acids (FFA) during the ripening of salted anchovy was studied. In the course of the curing process, the content of free fatty acids (FFA) in the muscle increased fifteen-fold, mostly in the first 100 days of the process. Each sample was subjected to sensory evaluations. A high correlation between FFA contents and sensory scores was found. Therefore the determination of FFA is proposed as an objective index to assess the ripening of salted anchovies.     

Two-dimensional diffusion of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) populations in stored wheat under constant environmental conditions

Insect movement inside a stored-grain bulk increases the chance for the pests to find biologically suitable locations for their development and multiplication. The movement of rusty grain beetle, Cryptolestes ferrugineus, adults was determined in a 0.1×1×1 m wooden box filled with wheat. There were 12 combinations of temperature (20, 25, 30, or 35 °C), number of adults (125, 250, or 500), moisture content (12.5, 14.5, or 16.5%), and time periods (3, 6, 12, 24 or 72 h) over which movement could occur. The diffusivities in each set of environmental conditions were calculated using a developed procedure (program) and experimental data. The diffusivity at 14.5% m.c. and 20 °C in the 24 h movement period was 2.5±0.3×10⁻⁴ m²/h. The diffusivity increased with increasing temperature, decreasing moisture contents, decreasing movement periods, and increasing insect numbers. Adult numbers in each section of the wooden box were predicted using an analytical model and calculated diffusivities. There were no significant differences between measured and predicted adult numbers. This research suggests that distribution and dispersal of the C. ferrugineus adults in stored wheat follow a diffusion pattern under constant environmental conditions.     

Proteolytic activity in cod (Gadus morhua) muscle during salt curing

The proteolytic activity of alkaline and acidic proteases in muscle from cod (Gadus morhua) was determined during salt curing. Proteolytic activity was determined for cod muscle that was either ice-stored or frozen-stored before it was subjected to three different salt treatments. The activity of the proteases chymotrypsin, trypsin, collagenase, elastase and cathepsin B/L was determined by the use of different fluorogenic substrates, while the total activity of acidic proteases was determined using haemoglobin as a substrate. The results indicated that the activity of the chymotrypsin, trypsin, collagenase and elastase was stimulated with increasing salt concentration, but seemed to decline again as the salt curing proceeded. Haemoglobin-hydrolysing activities, however, seemed to decrease with increasing concentration of salt in the muscle tissue.     

Changes in lipids during different sterilizing conditions in canning albacore (Thunnus alalunga) in oil

The effects on muscle lipid deterioration of initial cooking and of three time/temperature processing combinations after 4 months storage of albacore tuna canned in oil were studied. Conjugated dienes only increased slightly on cooking but thiobarbituric acid index increased and fell on canning; free fatty acids (FFA) increased with some canning. Polyene index and polyunsaturated fatty acids (PUFA) content provided higher values with higher temperature, shorter time processing.     

Chromium isotope fractionation during reduction of Cr(VI) under saturated flow conditions

Chromium isotopes are potentially useful indicators of Cr(VI) reduction reactions in groundwater flow systems; however, the influence of transport on Cr isotope fractionation has not been fully examined. Laboratory batch and column experiments were conducted to evaluate isotopic fractionation of Cr during Cr(VI) reduction under both static and controlled flow conditions. Organic carbon was used to reduce Cr(VI) in simulated groundwater containing 20 mg L(-1) Cr(VI) in both batch and column experiments. Isotope measurements were performed on dissolved Cr on samples from the batch experiments, and on effluent and profile samples from the column experiment. Analysis of the residual solid-phase materials by scanning electron microscopy (SEM) and by X-ray absorption near edge structure (XANES) spectroscopy confirmed association of Cr(III) with organic carbon in the column solids. Decreases in dissolved Cr(VI) concentrations were coupled with increases in δ(53)Cr, indicating that Cr isotope enrichment occurred during reduction of Cr(VI). The δ(53)Cr data from the column experiment was fit by linear regression yielding a fractionation factor (α) of 0.9979, whereas the batch experiments exhibited Rayleigh-type isotope fractionation (α = 0.9965). The linear characteristic of the column δ(53)Cr data may reflect the contribution of transport on Cr isotope fractionation.     

Effects of water activity on pigments in dried laver (Porphyra) during storage

Degradation of chlorophyll, carotenoids, and phycobilins in dried laver (Porphyra) was studied during storage at water activities (Aw) of 0.112, 0.316, 0.484, 0.747, or 0.890 in the dark at 40°C for 15 days. The chlorophyll, carotenoid, and phycobilin contents were determined using HPLC and spectrophotometry. The chorophyll a, carotenoid, and phycobilin contents in dried laver decreased with storage time in the dark, and degradation was increased and accelerated as the Aw value increased. Among pigments, chlorophyll a was degraded at the highest rate, and differences in degradation rates among pigments became greater as the Aw value increased. Phycoerythrin was more stable than phycocyanin. Changes in the Aw value affected degradation of phycocyanin and chlorophyll more than phycoerythrin or carotenoids. Control of the Aw value can improve the color stability of dried laver in the dark.     

Effect of environmental stress during tuber development on accumulation of glycoalkaloids in potato (Solanum tuberosum L)

The effects of low temperature and of combined stresses, cool temperature and waterlogging and also warm temperature and drought, on potato tuber glycoalkaloid levels were investigated, with emphasis on comparison of tubers of similar size. The early maturing cultivars Home Guard, Rocket and British Queen were grown under favourable controlled environment conditions (18/14 °C day/night temperature, 14 h photoperiod) until the imposition of treatments after the start of tuber initiation. Transfer to low temperature (12/9 °C) did not increase total glycoalkaloid concentration in any of the three cultivars. However, waterlogging at 12/9 °C increased total glycoalkaloid concentration during the later stages of development of British Queen. Drought stress at 24/18 °C also increased total glycoalkaloid concentration in British Queen, although the response varied between individual tubers of similar size. Total glycoalkaloid concentrations in tubers of Rocket were not affected by the combined stress treatments, and any effects on Home Guard were very much less than on British Queen. © 1999 Society of Chemical Industry     

Proteolytic activity (aspartic endoproteinase and carboxypeptidase) of cocoa bean during fermentation

This study was carried out to examine the changes in cocoa aspartic endoproteinase and carboxypeptidase activities, mass pH and temperature during 144 h (6 days) of fermentation using shallow wooden boxes. The results showed that at 72 h of fermentation, the activity of aspartic endoproteinase was higher than the original value. However, at 96 h the carboxypeptidase activity was higher than its original activity. The study also found a high correlation 0·99 (P<0·05) between the mass temperature with the aspartic endoproteinase at 48 h of fermentation. No correlation was found between the mass pH and temperature with the carboxypeptidase during fermentation. The degradation of vicilin-class globulin was about 88·8% and that of albumin was 47·4% at the end of fermentation. © 1998 SCI.     

Varietal and environmental differences in the proteins of the groundnut (arachis hypogaea)

The arachin and conarachin fractions were extracted from 8 samples of groundnut of different varieties grown in different locations. Marked variations in the electro-phoretic patterns, especially of the conarachin fractions, were observed and the amino acid composition of the fractions showed highly significant differences. These differences appeared to be both varietal and environmental in origin.     

The effect of killing conditions on the structural changes in vanilla (Vanilla planifolia, Andrews) pods during the curing process

The effect of seven methods of killing vanilla ( Vanilla planifolia , Andrews) pods on disassembly of the cell wall was studied. The following methods of plant killing were considered in this study: pod immersions in hot water under three conditions (65 °C for 3 min, 70 °C for 2 min, 80 °C for 10 s each of three times in 30 s intervals), pod immersions in 1% NaOH at 22 °C or 65 °C for 3 min, pod immersions in 95% ethanol at 22 °C for 60 min, and freezing at −10 °C for 24 h. Two procedures of vanilla pod killing, pod freezing at −10 °C for 24 h or pod immersions in hot water at 80 °C for 10 s each of three times in 30 s intervals, provoked the deepest and fastest disassembly of the cell wall structure and the successive cell content blending of the vanilla pod during the 8 days after curing.     

History and environmental impact of mining activity in Celtic Aeduan territory recorded in a peat bog (Morvan, France)

The present study aims to document historical mining and smelting activities by means of geochemical and pollen analyses performed in a peat bog core collected around the Bibracte oppidum (Morvan, France), the largest settlement of the great Aeduan Celtic tribe (ca. 180 B.C. to 25 A.D.). The anthropogenic Pb profile indicates local mining operations starting from the Late Bronze Age, ca. cal. 1300 B.C. Lead inputs peaked at the height of Aeduan civilization and then decreased after the Roman conquest of Gaul, when the site was abandoned. Other phases of mining are recognized from the 11th century to modern times. They have all led to modifications in plant cover, probably related in part to forest clearances necessary to supply energy for mining and smelting. Zn, Sb, Cd, and Cu distributions may result from diffusional and biological processes or from the influence of groundwater and underlying mineral soil, precluding their interpretation for historical reconstruction. The abundance of mineral resources, in addition to the strategic location, might explain why early settlers founded the city of Bibracte at that particular place. About 20% of the anthropogenic lead record was accumulated before our era and about 50% before the 18th century, which constitutes a troublesome heritage. Any attempts to develop control strategies in accumulating environments should take into account past human activities in order to not overestimate the impact of contemporary pollution.     

Enzymatic oxidative activity in sardine (Sardina pilchardus) and herring (Clupea harengus) during chilling and correlation with quality

 Enzymatic oxidative activity of two fatty fish species, sardine (Sardina pilchardus) and herring (Clupea harengus), was studied during chilled storage. Lipoxygenase enzyme activity was isolated and tested by measuring the hydroperoxides produced after induced oxidation of arachidonic and docosahexaenoic fatty acids. The most abundant degradation products of the hydroperoxides formed were 12- and 16-hydroxy acids which were detected by HPLC. Lipoxygenases were concentrated in the skin tissue of fish, and were active for up to 48 h of chilled storage. The pro-oxidative activity due to haem proteins continued for longer than that due to lipoxygenase. Trends of fluorescent formation resulting from interaction between oxidation products and biological amino constituents were compared with the pro-oxidative activities to establish correlations with quality loss during chilling. Received: 29 December 1998 / Revised version: 14 March 1999     

Chemical changes and diastatic activity in grains of sorghum (Sorghum bicolor) cultivars during germination

Grain samples from nine sorghum (Sorghum bicolor (L) Moench) cultivars were germinated for 16, 48, 96 and 144 h, and changes in their diastatic activity, protein, starch, soluble sugars, tannin and total phenols contents were studied. The diastatic activity increased up to 96 h of germination and decreased at 144 h. Diastatic activity showed significant variation among cultivars, which ranged from 10.0 to 88.3 units at 48 h and from 20.0 to 150.4 units at 96 h germination. In general, starch content decreased while soluble sugars increased during germination. Variation in protein content during germination was appreciable among the cultivars.     

Increase of essential amino acids in the bovine uterine lumen during preimplantation development

Amino acids (AAs) are crucial for the developing conceptus prior to implantation. To provide insights into the requirements of the bovine embryo, we determined the AA composition of the uterine fluid. At days 12, 15, and 18 post-estrus, the uteri of synchronized pregnant and non-pregnant Simmental heifers were flushed for the analysis of 41 AAs and their derivatives by liquid chromatography-tandem mass spectrometry. The ipsilateral endometrium was sampled for quantitative PCR. In addition to a pregnancy-dependent increase of the essential AAs (P<0.01), we detected elevated concentrations for most non-essential proteinogenic AAs. Histidine (His) and the expression of the His/peptide transporter solute carrier 15A3 (SLC15A3) were significantly increased at day 18 of pregnancy in vivo. In addition, SLC15A3 was predominantly stimulated by trophoblast-derived interferon-τ in stroma cells of an in vitro co-culture model of endometrial cells. Our results show an increased concentration of AAs most likely to optimally provide the elongating pre-attachment conceptus with nutrients.     

Variability of the lipolytic activity and volatile molecules production by a strain of Yarrowia lipolytica in pork fat and its dependence on environmental conditions

The effects of selected variables, i.e. temperature, water activity and yeast inoculation level, on the lipolytic pattern and volatile production by Yarrowia lipolytica Y16A (chosen on the basis of a previous screening) were assessed. The variables were varied according to a central composite design and the models obtained enabled evaluation and weighting of the effects of the independent variables on the free fatty acids (FFAs) and volatile profiles in pork fat based medium. The polynomial models showed the levels temperature, water activity of the pork fat based system and yeast strain inoculation were able to maximize the release of specific FFAs or molecules of sensory importance.     

Effect of coupled dissolution and redox reactions on Cr(VI)aq attenuation during transport in the sediments under hyperalkaline conditions

Aluminum-rich, hyperalkaline (pH > 13.5) and saline high-level nuclear waste (HLW) fluids at elevated temperatures (>50 degrees C), that possibly contained as much as 0.41 mol L(-1) Cr(VI), accidentally leaked to the sediments at the Hanford Site, WA. These extreme conditions promote base-induced dissolution of soil minerals which may affect Cr(VI)aq mobility. Our objective was to investigate Cr(VI)aq transport in sediments leached with HLW simulants at 50 degrees C, under CO2 and O2 free conditions. Results demonstrated that Cr(VI)aq fate was closely related to dissolution, and Cr(VI)aq mass loss was negligible in the first pore volumes but increased significantly thereafter. Similar to dissolution, Cr(VI)aq attenuation increased with increasing fluid residence time and NaOH concentration but decreased with Al concentrations in the leaching solutions. Aqueous Cr(VI) removal rate half-lives varied from 1.2 to 230 h with the fastest at the highest base concentration, lowest Al concentration, greatest reaction time, and lowest Cr(VI) concentration in the leaching solution. The rate of Cr(VI) removal (normalized to 1 kg of solution) varied from 0.83 x 10(-9) (+/-0.44 x 10(-9)) to 9.16 x 10(-9) (+/-1.10 x 10(-9)) mol s(-1). The predominant mechanism responsible for removing Cr(VI) from the aqueous phase appears to be homogeneous Cr(VI) reduction to Cr(III) by Fe(II) released during mineral dissolution. Cr(VI)aq removal was time-limited probably because it was controlled by the rate of Fe(II) release into the soil solution upon mineral dissolution, which was also a time-limited process, and other processes that may act to lower Fe(II)aq activity.