不同居群无患子果实组成比较研究

无患子是一种广泛分布于我国南方的乔木,本文针对不同居群无患子全果的物理组成、种仁油脂及氨基酸组成等方面进行比较研究.福建无患子种仁含油率最高,达到42.8％;四川无患子种子含油率最高,达到13.7％.无患子油脂的脂肪酸碳链长度为C16～C24,其中C16～C20的脂肪酸均占92％以上,不饱和脂肪酸79％～85％.种仁氨...     

Unusual heme iron-lipid acyl chain coordination in Escherichia coli flavohemoglobin

Escherichia coli flavohemoglobin is endowed with the notable property of binding specifically unsaturated and/or cyclopropanated fatty acids both as free acids or incorporated into a phospholipid molecule. Unsaturated or cyclopropanated fatty acid binding to the ferric heme results in a spectral change observed in the visible absorption, resonance Raman, extended x-ray absorption fine spectroscopy (EXAFS), and x-ray absorption near edge spectroscopy (XANES) spectra. Resonance Raman spectra, measured on the flavohemoglobin heme domain, demonstrate that the lipid (linoleic acid or total lipid extracts)-induced spectral signals correspond to a transition from a five-coordinated (typical of the ligand-free protein) to a hexacoordinated, high spin heme iron. EXAFS and XANES measurements have been carried out both on the lipid-free and on the lipid-bound protein to assign the nature of ligand in the sixth coordination position of the ferric heme iron. EXAFS data analysis is consistent with the presence of a couple of atoms in the sixth coordination position at 2.7 A in the lipid-bound derivative (bonding interaction), whereas a contribution at 3.54 A (nonbonding interaction) can be singled out in the lipid-free protein. This last contribution is assigned to the CD1 carbon atoms of the distal LeuE11, in full agreement with crystallographic data on the lipid-free protein at 1.6 A resolution obtained in the present work. Thus, the contributions at 2.7 A distance from the heme iron are assigned to a couple of carbon atoms of the lipid acyl chain, possibly corresponding to the unsaturated carbons of the linoleic acid.     

Bioenergetic considerations in the improvement of oil content and quality in oil-seed crops

Summary Production values (PVs), defined as the weight of the end product/weight of the substrate required for carbon skeletons and energy production, were calculated for plant fatty acids. The PVs varied from 0.361 to 0.300 with linolenic acid having the lowest value. In general, the PVs of unsaturated fatty acids were lower than those of saturated fatty acids of similar chain lengths. Using this basic information, PVs of (A) oils from different oilseed crops, based on their standard fatty acid composition and (B) seed biomass with specified oil content and fatty acid composition were calculated. 1/PV gives the glucose required for the biosynthesis of 1 g end product and thus an estimate of the photosynthate requirement for the desired breeding goal can be estimated. Such calculations show that increasing oil percentage in seeds has a maximum energy cost when the increase in oil is associated with a decrease in the amount of carbohydrates where there is no change in protein concentration. Reduction of erucic acid content in the rapeseed oil did not alter its PV. It is inferred that there are no serious bioenergetic constraints in altering the fatty acid composition.     

Fluid phase lipid areas and bilayer thicknesses of commonly used phosphatidylcholines as a function of temperature

The structural parameters of fluid phase bilayers composed of phosphatidylcholines with fully saturated, mixed, and branched fatty acid chains, at several temperatures, have been determined by simultaneously analyzing small-angle neutron and X-ray scattering data. Bilayer parameters, such as area per lipid and overall bilayer thickness have been obtained in conjunction with intrabilayer structural parameters (e.g. hydrocarbon region thickness). The results have allowed us to assess the effect of temperature and hydrocarbon chain composition on bilayer structure. For example, we found that for all lipids there is, not surprisingly, an increase in fatty acid chain trans-gauche isomerization with increasing temperature. Moreover, this increase in trans-gauche isomerization scales with fatty acid chain length in mixed chain lipids. However, in the case of lipids with saturated fatty acid chains, trans-gauche isomerization is increasingly tempered by attractive chain-chain van der Waals interactions with increasing chain length. Finally, our results confirm a strong dependence of lipid chain dynamics as a function of double bond position along fatty acid chains.     

Effects of oven- or freeze-drying on chemical composition and NIR spectra of pasture silage

In order to assess effects of drying method on chemical composition and NIR spectra of pasture silage, 20 samples of silages from permanent pastures of different qualities were subsampled and dried either by forced draught oven at 65°C or freeze-dried. Samples were analysed for crude protein (CP), crude fibre (CF), neutral detergent fibre (NDF), acid detergent fibre (ADF), gross energy (GE) and in vitro digestible organic matter in the dry matter (DOMD) and composition expressed on a dry-matter (DM) basis, either obtained as oven 105°C DM (DM_105°) or toluene DM (DM_tol). Effects of the drying method on chemical composition were estimated by paired comparisons. Near-infrared reflectance (NIR) spectra were taken and the difference spectra between treatments for each sample were plotted in order to visually inspect effects of treatments, either as log 1/R or transformed by their first derivative. Principal components explaining spectral variability were computed and samples graphically displayed according to the eigenvalues of the first (1 and 2), or second (2 and 3) pairs of principal components. Oven-drying resulted in a reduction in CP (p<0.02) content and an increase in CF (p<0.1), NDF (p<0.001) and ADF (p<0.06) content of silages, when expressed on a DM_105° basis. When expressed on a DM_tol basis, a reduction in CP (p<0.02) and DOMD (p<0.06) content was observed with oven drying, but fibre fractions were not affected (p>0.1). Effects of the drying treatment were visually apparent on NIR spectra when plotted as log 1/R against wavelengths, mainly as a baseline shift. Difference spectra (OD − FD), both as log 1/R and its first derivative, showed consistent absorption bands, indicative of different molecular responses of OD and FD silages to incident light. Plotting samples according to eigenvalues of the first two or second two principal components suggests that drying methods affect the distribution of samples. This is also indicative of an effect of drying treatment on spectral features and reinforces the general advice that sample processing should be consistent in order to avoid adding errors to NIR analysis.     

Fatty acid composition of cardiolipin from guinea pig Harderian gland

The fatty acid composition of cardiolipin from the Harderian gland of guinea pig was examined by gas chromatography and gas chromatography-mass spectrometry. At least 33 kinds of fatty acids were detected. Oleic acid was the most prominent component, accounting for 18.2 mol% of the total fatty acids. About 70.2 mol% of fatty acids had methyl branches. Ethyl branches were also detected (1.3 mol%). Straight chain saturated acids comprised only 10.3 mol%. On the other hand, linoleic, linolenic, and arachidonic acids were not found in this lipid. The 2-(2'-) acyl moieties contained larger amounts of oleic acid and smaller amounts of branched chain acids than the 1-(1'-)acyl moieties, but the saturated straight chain acids showed even distribution between the 1-(1'-) and 2-(2'-)positions. The fatty acids of cardiolipin from the liver of the same animal were also examined. Linoleic acid was the most abundant component (66.9 mol%), and saturated straight chain acids occupied 21.9 mol%. Branched chain acids were detected but comprised only 11.2 mol%.     

Determination of fatty acid and triacylglycerol composition of human very-low-density lipoproteins

The fatty acid composition of human very-low-density lipoproteins (VLDL) was studied in a population from western Andalusia with a diet in which the fat content came mainly from olive oil. The lipid composition of VLDL, including the fatty acid composition of the phospholipids and triacylglycerols, was examined by capillary gas chromatography. Twenty-five peaks were resolved, ranging in chain length from 14 to 24 carbon atoms, including geometric and positional isomers. The major fatty acids present in phospholipids were 16:0, 18:0, 18:1(n − 9) and 18:2(n − 6), and in triacylglycerols were 18:1(n − 9), 16:0 and 18:2(n − 6). The major triacylglycerol was POO, followed by PLO and OOO. MLP, PPS and LLL were absent. The presence of a large amount of OOO in this fraction demonstrates that the triacylglycerol composition of the VLDL depends on the type of diet consumed.     

Effect of modification of the length and flexibility of the acyl carrier protein-thioesterase interdomain linker on functionality of the animal fatty acid synthase

A natural linker of approximately 20 residues connects the acyl carrier protein with the carboxy-terminal thioesterase domain of the animal fatty acid synthase. This study examines the effects of changes in the length and amino acid composition of this linker on catalytic activity, product composition, and segmental motion of the thioesterase domain. Deletion of 10 residues, almost half of the interdomain linker, had no effect on either mobility of the thioesterase domain, estimated from fluorescence polarization of a pyrenebutyl methylphosphono moiety bound covalently to the active site serine residue, or functionality of the fatty acid synthase; further shortening of the linker limited mobility of the thioesterase domain and resulted in reduced fatty acid synthase activity and an increase in product chain length from 16 to 18 and 20 carbon atoms. Surprisingly, however, even when the entire linker region was deleted, the fatty acid synthase retained 28% activity. Lengthening of the linker, by insertion of an unusually long acyl carrier protein-thioesterase linker from a modular polyketide synthase, increased mobility of the thioesterase domain without having any significant effect on catalytic properties of the complex. Interdomain linkers could also be used to tether, to the acyl carrier protein domain of the fatty acid synthase, a thioesterase active toward shorter chain length acyl thioesters generating novel short-chain fatty acid synthases. These studies reveal that although truncation of the interdomain linker partially impacts the ability of the thioesterase domain to terminate growth of the acyl chain, the overall integrity of the fatty acid synthase is quite tolerant to moderate changes in linker length and flexibility. The retention of fatty acid synthesizing activity on deletion of the entire linker region implies that the inherent flexibility of the phosphopantetheine "swinging arm" also contributes significantly to the successful docking of the long-chain acyl moiety in the thioesterase active site.     

Membrane lipid biosynthesis in Acholeplasma laidlawii b: elongation of medium- and long-chain exogenous fatty acids in growing cells

The chain elongation of a wide variety of exogenous fatty acids and the subsequent incorporation of the chain elongation products into the total membrane lipids of Acholeplasma laidlawii B were systematically studied. Within each chemical class of fatty acids examined, the extent of chain elongation increased with increases in chain length, reached a maximum value, and then declined with further increases in chain length. Depending on chemical structure, exogenous fatty acids containing less than 6 to 9 carbon atoms or more than 15 to 18 carbon atoms were not substrates for the chain elongation system. The substrate specificity of this fatty acid elongation system was strikingly broad, and straight-chain, methyl isobranched, and methyl anteisobranched saturated fatty acids, as well as cis- and trans-monounsaturated, cis-cyclopropane, and cis-polyunsaturated fatty acids, underwent chain elongation in vivo. The extent of chain elongation and the average chain length of the primary elongation products correlated well with the physical properties (melting temperatures) of the exogenous fatty acid substrates. The specificity of fatty acid chain elongation in A. laidlawii B maintained the fluidity and physical state of the membrane lipids within a rather wide but definitely limited range. The fatty acid chain elongation system of this organism could be markedly influenced by the presence of a second exogenous fatty acid that was not itself a substrate for the chain elongation system but was incorporated directly into the membrane lipids. The presence of a relatively low-melting exogenous fatty acid increased both the extent of chain elongation and the average chain length of the elongation products generated, whereas the presence of a relatively high-melting fatty acid had the opposite effect. The extent of chain elongation and nature of the elongation products formed were not, however, dependent on the fluidity and physical state of the membrane lipids per se. The second exogenous fatty acid appeared instead to exert its characteristic effect by competing with the chain elongation substrate and elongation products for the stereospecific acylation of positions 1 and 2 of sn-glycerol-3-phosphate. The similar effects of alterations in environmental temperature, cholesterol content, and exposure to the antibiotic cerulenin on the fatty acid chain elongation and de novo biosynthetic activities suggested that the chain elongation system of this organism may be a component of the de novo biosynthetic system.     

Assessment of in-line near-infrared spectroscopy for continuous monitoring of fermentation processes

The application of NIR in-line to monitor and control fermentation processes was investigated. Determination of biomass, glucose, and lactic and acetic acids during fermentations of Staphylococcus xylosus ES13 was performed by an interactance fiber optic probe immersed into the culture broth and connected to a NIR instrument. Partial least squares regression (PLSR) calibration models of second derivative NIR spectra in the 700-1800 nm region gave satisfactory predictive models for all parameters of interest: biomass, glucose, and lactic and acetic acids. Batch, repeated batch, and continuous fermentations were monitored and automatically controlled by interfacing the NIR to the bioreactor control unit. The high frequency of data collection permitted an accurate study of the kinetics, supplying lots of data that describe the cultural broth composition and strengthen statistical analysis. Comparison of spectra collected throughout fermentation runs of S. xylosus ES13, Lactobacillus fermentum ES15, and Streptococcus thermophylus ES17 demonstrated the successful extension of a unique calibration model, developed for S. xylosus ES13, to other strains that were differently shaped but growing in the same medium and fermentation conditions. NIR in-line was so versatile as to measure several biochemical parameters of different bacteria by means of slightly adapted models, avoiding a separate calibration for each strain.     

Cultivation ofCandida lipolytica 4-1 on hydrocarbons

The length of the carbon chain of the hydrocarbon substrate affects markedly the fatty acid composition in the cell lipids of the yeastCandida lipolytica 4-1. During cell growth onn-hexadecane dissolved in deparaffinated gas oil, direct incorporation of palmitic acid into lipids takes place. During growth onn-dodecane, on the other hand, an immediate synthesis and incorporation into oleic acid is observed. The cells contain only little lauric acid (maximum 11%). During fermentation of then-alkanes dissolved in deparaffinated gas oil which contains a mixture of isoalkanes, alkylated aromatic and cyclic hydrocarbons, free fatty acids accumulate in the oil phase. The fatty acid composition in the oil differs markedly according to the growth stage of cells. At the beginning of the logarithmic phase of growth, the fatty acid composition in the oil phase reflects the acid composition in the cell lipids, toward the end of cell growth, the cooxidation products of the isoalkanes accumulate. The aqueous phase contains lower fatty acids and cooxidation products of isoalkanes and of alkylated aromatic and alicyclic hydrocarbons. Part III. Oxidation and Utilization of Individual Pure Hydrocarbons—seeFolia Microbiol. 14,334 (1969).     

The Emergence and Evolution of Life in a “Fatty Acid World” Based on Quantum Mechanics

Quantum mechanical based electron correlation interactions among molecules are the source of the weak hydrogen and Van der Waals bonds that are critical to the self-assembly of artificial fatty acid micelles. Life on Earth or elsewhere could have emerged in the form of self-reproducing photoactive fatty acid micelles, which gradually evolved into nucleotide-containing micelles due to the enhanced ability of nucleotide-coupled sensitizer molecules to absorb visible light. Comparison of the calculated absorption spectra of micelles with and without nucleotides confirmed this idea and supports the idea of the emergence and evolution of nucleotides in minimal cells of a so-called Fatty Acid World. Furthermore, the nucleotide-caused wavelength shift and broadening of the absorption pattern potentially gives these molecules an additional valuable role, other than a purely genetic one in the early stages of the development of life. From the information theory point of view, the nucleotide sequences in such micelles carry positional information providing better electron transport along the nucleotide-sensitizer chain and, in addition, providing complimentary copies of that information for the next generation. Nucleotide sequences, which in the first period of evolution of fatty acid molecules were useful just for better absorbance of the light in the longer wavelength region, later in the PNA or RNA World, took on the role of genetic information storage.     

Quantitative gas-liquid chromatographic analysis of rodent milk triglycerides

A comparison has been made of the milk and adipose tissue triglycerides of rabbits and guinea pigs provided with one diet and of rats and mice provided with another. Both intact triglycerides and component fatty acids were analyzed by gas-liquid chromatography. Good correlation of the data obtained by the two techniques was obtained by calculating the average chain length of the fatty acid moieties. Little difference was found in the triglyceride composition of the adipose tissue of the different species. However, wide variation in the triglyceride composition of the milk was found between the species: the average fatty acid chain length in milk was 11.7 for rabbits, 14.2 for rats, 15.3 for mice, and 17.2 for guinea pigs. The corresponding values for adipose tissue were in the range 16.9-17.4 in all animals. The significance of enzymes that synthesize short-chain fatty acids in mammary gland is discussed.     

DIFFERENCES IN PHOTOSYNTHESIS-ASSOCIATED PROPERTIES OF THE BLUEGREEN ALGA SYNECHOCOCCUS CEDRORUM CROWN AT 30 AND 40 C1

The growth of Synechococcus cedrorum Saug. (UTEX 1191) at 40 C resulted in structural and functional alteratons relative to cells grown at 30 C. Structural variations included cell morphology and the chemical composition of the membrane. Growth at 40 C. produced cells that were longer and thinner than those at 30 C. The fatty acid composition changed substantially upon growth at 40 C. yielding a distribution with a higher ratio of: i) saturated to unsaturated fatty acids and; ii) longer chain unsaturated fatty acids. Furthermore, the pattern of membrane proteins as determined by sodium dodecyl sulfate electrophoresis was distinctly different. The functional changes were typified by photosynthetic rates which were approximately half those of the 30 C grown cells. A number of spectral parameters were also seen to change in 40 C. grown cells: absorption spectra indicated a higher phycocyanin : chlorophyll ratio. Low temperature fluorescence spectra were consistent with a lowered efficiency of energy transfer from phycocyanin to chlorophyll. It is suggested that the fatty acid changes at 40 C. yield a more fluid membrane which is responsible for the functional alterations. The modification of phycocyanin. chlorophyll ratios, as well as the appearance of P750, is discussed with respect to membrane fluidity.     

Biochemical and ultrastructural studies on the interaction of basic proteins with mitochondria: a primary effect on membrane configuration

The cytochrome P-450_K containing monooxygenase system of rat kidney cortex microsomes catalyzes the hydroxylation of various saturated fatty acids of medium chain length to the corresponding ω- and (ω-1)-hydroxy derivatives. The hydroxylation activity, as well as the ratio between the two hydroxylated products, vary with the carbon chain length of the fatty acid. Optimal hydroxylation activity is observed with myristic acid which yields the 13- and 14-hydroxylated products at a ratio of about 1. The ω/(ω-1)-hydroxylation ratio decreases with increasing carbon chain length of the fatty acid. On the other hand, with lauric acid as a substrate the ratio between ω- and (ω-1)-hydroxylation does not change significantly with varying time of incubation or substrate concentration, or incubation in a medium containing D₂O or after induction of enhanced hydroxylation activity by starvation of the animals. Furthermore, 12-hydroxylauric acid and capric acid—which is almost exclusively ω-hydroxylated by rat kidney cortex microsomes—inhibit both 11- and 12-hydroxylation of lauric acid to a similar extent whereas 11-hydroxylauric acid does not seem to inhibit either 11- or 12-hydroxylation.C₁₀-C₁₆ fatty acids produce the type I spectral change upon addition to rat kidney cortex microsomes and seem to interact with similar amounts of the cytochrome P-450_K present in these particles. In agreement with the metabolic studies, 12-hydroxylauric acid interacts with cytochrome P-450_K giving rise to a reverse type I spectral change, whereas 11-hydroxylauric acid does not produce an observable spectral change. Finally, results of binding experiments with a series of derivatives of dodecane suggest that type I binding to cytochrome P-450_K requires, besides a proper chain length, the presence of a carbonyl group together with an electron pair on a neighboring atom at the end of the carbon chain. A chain length of 14 carbon atoms seems to be optimal and it is suggested that this chain length may correspond to the distance between a possible binding site and the catalytic site of cytochrome P-450_K     

A spectral analysis of stem bark for boreal and temperate tree species

The woody material of forest canopies has a significant effect on the total forest reflectance and on the interpretation of remotely sensed data, yet research on the spectral properties of bark has been limited. We developed a novel measurement setup for acquiring stem bark reflectance spectra in field conditions, using a mobile hyperspectral camera. The setup was used for stem bark reflectance measurements of ten boreal and temperate tree species in the visible (VIS) to near‐infrared (NIR) (400–1000 nm) wavelength region. Twenty trees of each species were measured, constituting a total of 200 hyperspectral reflectance images. The mean bark spectra of species were similar in the VIS region, and the interspecific variation was largest in the NIR region. The intraspecific variation of bark spectra was high for all studied species from the VIS to the NIR region. The spectral similarity of our study species did not correspond to the general phylogenetic lineages. The hyperspectral reflectance images revealed that the distributions of per‐pixel reflectance values within images were species‐specific. The spectral library collected in this study contributes toward building a comprehensive understanding of the spectral diversity of forests needed not only in remote sensing applications but also in, for example, biodiversity or land surface modeling studies.     

Monitoring of hydroxyl groups in wood during heat treatment using NIR spectroscopy

This paper deals with the evaluation of thermally treated wood by near-infrared (NIR) spectroscopy. In the NIR second derivative spectrum, the absorption band at 6913 cm(-1) appeared with the procession of heat treatment, which conclusively assigned to the phenolic hydroxyl groups due to the lignin in comparison with the spectrum of acetylated spruce wood. As a result of the changes in the ratio of the areal integral calculated from spectral separation in the region of hydroxyl groups (7200-6100 cm(-1)) by the Gauss-Newton method, it was clear that the degradation of hydroxyl group in the cellulose started predominantly from the amorphous region and followed to semicrystalline and crystalline region. There was an obvious correlation between the weight decrement of wood and the decrement of hydroxyl groups in the cellulose by heat treatment.     

Polyphosphoinositides are derived from ether-linked inositol glycerophospholipids in rat brain

Membrane inositol glycerophospholipid (IGP) is metabolized to phosphatidylinositol-4-phosphate (PIP), phosphatidylinositol-4, 5-bisphosphate (PIP2), and inositol triphosphate (IP3) in signaling transduction. This study was carried out to determine the subclasses of IGP involved in signaling pathway. The acyl chain moieties of the phospholipids are easily modulated by dietary fatty acids. We analyzed acyl chain composition of IGP 3-subclasses, PIP and PIP2 from rat brain after feeding sunflower seed oil enriched with linoleic acid or fish oil high in eicosapentaenoic acid and docosahexaenoic acid. Long chain polyunsaturated fatty acids (LCPUFA) as eicosapentaenoic acid and docosahexaenoic acid were not incorporated into ether-linked IGP (alkenylacylglycerophosphoinositol and alkylacyl-glycerophosphoinositol), PIP and PIP2, while diacyl-glycerophosphoinositol (GPI) contained high LCPUFA. These results suggest that PIP might be phosphorylated from only the ether-linked IGP (alkenylacyl- and alkylacyl species) but not from diacyl subclass for signals to intracellular responses in the plasma membrane of rat brain.     

Formation and degradation of lipid bodies found in the riboflavin-producing fungus Ashbya gossypii

Microdroplets in the hyphae of Ashbya gossypii were found to become stained by Nile red. Purification of the stainable substance showed that the yellow fluorescent bodies consisted of triacylglycerol. During growth on glucose as the carbon source 8%–12% of the mycelial dry weight was found to be neutral lipid. When glucose declined in the medium, the content decreased to 3%–4% and the respiration quotient shifted to 0.6 indicating a reserve function of the fat. The fatty acid composition of the storage lipid was found to be strongly influenced by the carbon source. Mycelia cultivated on glucose contained 5% linoleic acid and 20% palmitoleic acid in their neutral fat while linoleic acid made up 54% and palmitoleic acid was not detectable (< 0.1%) in soybean-oil-grown mycelia. When plant oil was given as the sole carbon source, the fatty acid composition of the storage lipid showed a high similarity to the fed fat. ¹⁴C-labelled free oleic acid added to a culture growing on soybean oil was immediately incorporated into the fungal lipid. A pulse of 0.9 g/l free palmitoleic acid, fed during growth on olive oil, increased the content of this particular fatty acid in the fungal triacylglycerol from 0.8% to 9.6%. In addition, a liberation of free fatty acid and diacylglyceride was found in the culture supernatant when pure triolein was given as the sole carbon source. Obviously, the fungus cleaved the lipid serving as the carbon source extracellularly and used the liberated fatty acids for its storage lipid formation.This paper is dedicated to Prof. Dr. F. Wagner on the occasion of his 65th birthday     

Toxicity of medium chain fatty acids to Penicillium crustosum Thom and their detoxification to methyl ketones

Conversion of medium chain length fatty acids into methyl ketones by some filamentous fungi is important in the development of flavour in the blue mould-ripened cheeses and in the promotion of ketonic rancidity in the lauric acid oils. The effect of fatty acid composition of single acid glycerides, pH, temperature and medium chain length fatty acids on conversion of fatty acids into methyl ketones has been studied with two strains of Penicillium crustosum Thom. Medium chain length fatty acids were fungitoxic. The minimum inhibitory concentration was 3776, 2884, 1723 and 3066 mg/l for the C6:0, 8:0, 10:0 and 12:0 acids, respectively, at pH 7·0 in liquid suspension culture. Evidence is provided to suggest that the cellular site for this conversion is the microbody. Growth of P. crustosum on single acid glycerides involves two distinct physiological processes; the first, a general inhibition of growth, and the second, a detoxification. The fatty acid composition and the slip point of the substrate are of paramount importance in these two processes.