Kinetics and mathematical modeling of infrared thin-layer drying of garlic slices

Drying of garlic slices in thin-layer have been studied with Infrared (IR) at 0.075, 0.15, 0.225 and 0.3 W cm^?2 radiation intensity and 0.75 and 1.25 m s^?1 air flow velocity. The results showed increasing in drying rate and decreasing at the time of drying with decreasing air flow velocity and increasing IR radiation intensity. The effective moisture diffusivity (D_eff) was obtained using Fick’s diffusion equation and its mean values ranged between 5.83×10^?11 and 7.66×10^?10 m² s^?1 for all investigated conditions. In addition, a third-order polynomial equation linking the effective moisture diffusivity and moisture content was found. Average activation energy increased with the decrease of IR radiation and increase of air flow velocity. Thirteen different mathematical models were verified with non-linear regression analysis for describing the garlic drying process. Modified Henderson and Pabis model presented the best prediction of the drying of garlic slices.     

In vitro stereoselective hydrolysis of diacylglycerols by hormone-sensitive lipase

Hormone-sensitive lipase (HSL) contributes importantly to the mobilization of fatty acids in adipocytes and shows a substrate preference for the diacylglycerols (DAGs) originating from triacylglycerols. To determine whether HSL shows any stereopreference during the hydrolysis of diacylglycerols, racemic 1,2(2,3)-sn-diolein was used as a substrate and the enantiomeric excess (ee%) of residual 1,2-sn-diolein over 2,3-sn-diolein was measured as a function of DAG hydrolysis. Enantiomeric DAGs were separated by performing chiral-stationary-phase HPLC after direct derivatization from lipolysis product extracts. The fact that the ee% of 1,2-sn-diolein over 2,3-sn-diolein increased with the level of hydrolysis indicated that HSL has a preference for 2,3-sn-diolein as a substrate and therefore a stereopreference for the sn-3 position of dioleoylglycerol. The ee% of 1,2-sn-diolein reached a maximum value of 36% at 42% hydrolysis. Among the various mammalian lipases tested so far, HSL is the only lipolytic carboxylester hydrolase found to have a pronounced stereospecificity for the sn-3 position of dioleoylglycerol.     

Comparative Assessment of SSR and AFLP Markers for Evaluation of Genetic Diversity and Conservation of Fig, <Emphasis Type="Italic">Ficus carica</Emphasis> L., Genetic Resources in Tunisia

This study characterises the genetic variability of fig, Ficus carica L., using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. It compares the efficiency and utility of the two techniques in detecting variation and establishing genetic relationships among Tunisian fig cultivars. Our results show that using both marker systems, the Tunisian fig germ plasm is characterised by having a large genetic diversity at the deoxyribonucleic acid level, as most of AFLP bands were detected and all SSR markers were polymorphic. In fact, 351 (342 polymorphic) and 57 (57 polymorphic) bands were detected using AFLP and SSR primers, respectively. SSR markers were the most polymorphic with an average polymorphic information content value of 0.94, while AFLP markers showed the highest effective multiplex ratio (56.9) and marker index (45.2). The effective marker index was recorded highest (4.19) for AFLP markers and lowest (0.70) for the SSR ones. Our results demonstrate that (1) independent as well as combined analyses of cluster analyses of SSR and AFLP fragments showed that cultivars are clustered independently from their geographical origin, horticultural classifications and tree sex; (2) the analysis of molecular variance allowed the partitioning of genetic variation within and among fig groups and showed greater variation within groups and (3) AFLP and SSR markers datasets showed positive correlation. This study suggests the SSR and AFLP markers are suitable for diversity analysis and cultivars fingerprinting. An understanding of the genetic diversity and population structure of F. carica in Tunisia can also provide insight into the conservation and management of this species.     

Use of an inhibitor to identify members of the hormone-sensitive lipase family

Hormone-sensitive lipase (HSL) contributes importantly to the mobilization of fatty acids from the triacylglycerols stored in adipocytes, which provide the main source of energy in mammals. On the basis of amino acid sequence alignments and three-dimensional structures, this enzyme was previously found to be a suitable template for defining a family of serine carboxylester hydrolases. In this study, the HSL family members are characterized rather on the basis of their inhibition by 5-methoxy-3-(4-phenoxyphenyl)-3H-[1,3,4]oxadiazol-2-one (compound 7600). This compound inhibits mammalian HSL as well as other HSL family members, such as EST2 from the thermophilic eubacterium Alicyclobacillus acidocaldarius and AFEST from the hyperthermophilic archaeon Archaeoglobus fulgidus. Various carboxylester hydrolases that are not members of the HSL family were found not to be inhibited by compound 7600 under the same experimental conditions. These include nonlipolytic hydrolases such as Torpedo californica acetylcholinesterase and pig liver esterase, as well as lipolytic hydrolases such as human pancreatic lipase, dog gastric lipase, Thermomyces lanuginosus lipase, and Bacillus subtilis LipA. When vinyl esters were used as substrates, the residual activity of HSL, AFEST, and EST2 decreased with an increase in compound 7600 concentration in the incubation mixture. The inhibitor concentration at which the enzyme activity decreased to 50% after incubation for 5 min was 70, 20, and 15 nM with HSL, AFEST, and EST2, respectively. Treating EST2 and AFEST with the inhibitor resulted in an increase in the molecular mass, as established by performing matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis. This increase in the molecular mass, which corresponds approximately to the molecular mass of the inhibitor, indicates that a covalent enzyme-inhibitor complex has been formed. Surface-enhanced laser desorption ionization time-of-flight mass spectrometry analysis of a trypsin digest of AFEST treated with the inhibitor or not treated showed the occurrence of an increase in the molecular masses of the "GESAGG"-containing peptide, which is compatible with the formation of a covalent complex with the inhibitor.     

The Farnesoid X Receptor Regulates Adipocyte Differentiation and Function by Promoting Peroxisome Proliferator-activated Receptor-γ and Interfering with the Wnt/β-Catenin Pathways

The bile acid receptor farnesoid X receptor (FXR) is expressed in adipose tissue, but its function remains poorly defined. Peroxisome proliferator-activated receptor-γ (PPARγ) is a master regulator of adipocyte differentiation and function. The aim of this study was to analyze the role of FXR in adipocyte function and to assess whether it modulates PPARγ action. Therefore, we tested the responsiveness of FXR-deficient mice (FXR^−/−) and cells to the PPARγ activator rosiglitazone. Our results show that genetically obese FXR^−/−/ob/ob mice displayed a resistance to rosiglitazone treatment. In vitro, rosiglitazone treatment did not induce normal adipocyte differentiation and lipid droplet formation in FXR^−/− mouse embryonic fibroblasts (MEFs) and preadipocytes. Moreover, FXR^−/− MEFs displayed both an increased lipolysis and a decreased de novo lipogenesis, resulting in reduced intracellular triglyceride content, even upon PPARγ activation. Retroviral-mediated FXR re-expression in FXR^−/− MEFs restored the induction of adipogenic marker genes during rosiglitazone-forced adipocyte differentiation. The expression of Wnt/β-catenin pathway and target genes was increased in FXR^−/− adipose tissue and MEFs. Moreover, the expression of several endogenous inhibitors of this pathway was decreased early during the adipocyte differentiation of FXR^−/− MEFs. These findings demonstrate that FXR regulates adipocyte differentiation and function by regulating two counteracting pathways of adipocyte differentiation, the PPARγ and Wnt/β-catenin pathways.     

Diversity and spatial genetic structure of natural Moroccan <Emphasis Type="Italic">Quercus susber</Emphasis> L. assessed by ISSR markers for conservation

Morocco is one of the most important regions of the world in terms of Quercus suber L. number and variation. This species is in decline due to several factors, which can lead to permanent loss of this resource. It would be essential to evaluate the genetic diversity in order to conserve maximum genetic variability of this species. The genetic diversity and differentiation of 16 sites from five regions representing the entire range of Moroccan Cork Oak were assessed. Twenty-three ISSR primers used generated 985 polymorphic fragments with an average of 42.8 bands per primer and showed 100% of polymorphism. The 173 individuals revealed a moderate level of genetic diversity at species level (I?=?0.27, He?=?0.161). The AMOVA showed that the highest level of diversity occurred within populations (64%), this was also confirmed by the coefficient of differentiation (Gst?=?0.47). The estimated gene flow (Nm?=?0.56) and the Mantel test revealed a significant correlation between geographic and genetic diversity (r?=?0.266; p?=?0.001). This genetic structure was further shown by the topology of the UPGMA, sPCA and STRUCTURE analysis. In addition, a core collection of 34 genotypes was established representing the essential diversity detected. This research advocates populations and individuals to preserve in order to improve and conserve this resource in the future.     

Freezing of fresh Barhi dates for quality preservation during frozen storage

Fresh harvested dates are perishable and there is a need for extending their shelf life while preserving their fresh like quality characteristics. This study evaluates three different freezing methods, namely cryogenic freezing (CF) using liquid nitrogen; individual quick freezing (IQF) and conventional slow freezing (CSF) in preserving the quality and stability of dates during frozen storage. Fresh dates were frozen utilizing the three methods. The produced frozen dates were frozen stored for nine months. The color values, textural parameters, and nutrition qualities were measured for fresh dates before freezing and for the frozen dates every three months during the frozen storage. The frozen dates’ color values were affected by the freezing method and the frozen storage period. There are substantial differences in the quality of the frozen fruits in favor of cryogenic freezing followed by individual quick freezing compared to the conventional slow freezing. The results revealed large disparity among the times of freezing of the three methods. The freezing time accounted to 10 min for CF, and around 80 min for IQF, and 1800 min for CSF method.     

Osmoadaptative responses in the rhizobia nodulating Acacia isolated from south-eastern Moroccan Sahara

Four strains of rhizobia nodulating Acacia were isolated from the Moroccan desert soil by trapping with seedlings of Acacia gummifera and Acacia raddiana, and were studied for their ability to tolerate high salinity and dryness conditions. The strains MDSMC 2, MDSMC 18 and MDSMC 50 were halotolerant (they tolerated up to 1 M NaCl) and they accumulated glutamate and mannosucrose. The synthesis of the latter solute, which is the major endogenous osmolyte, is partially repressed in the presence of glycine betaine. The strain MDSMC 34 was less halotolerant (growth inhibited by a concentration greater than 0.5 M NaCl), and accumulated trehalose (as the main endogenous osmolyte) and glutamate. Rhizobia from the Moroccan desert soil were highly resistant to desiccation and their tolerance to dryness was stimulated by osmotic pretreatment. Thus, the accumulation of mannosucrose or trehalose by desert rhizobia represents both an osmoadaptative response and a part of a desiccation tolerance mechanism.     

An ultraviolet spectrophotometric assay for the screening of sn-2-specific lipases using 1,3-O-dioleoyl-2-O-α-eleostearoyl-sn-glycerol as substrate

In the present study, we propose a continuous assay for the screening of sn-2 lipases by using triacylglycerols (TAGs) from Aleurites fordii seed (tung oil) and a synthetic TAG containing the α-eleostearic acid at the sn-2 position and the oleic acid (OA) at the sn-1 and sn-3 positions [1,3-O-dioleoyl-2-O-α-eleostearoyl-sn-glycerol (sn-OEO)]. Each TAG was coated into a microplate well, and the lipase activity was measured by optical density increase at 272 nm due to transition of α-eleostearic acid from the adsorbed to the soluble state. The sn-1,3-regioselective lipases human pancreatic lipase (HPL), LIP2 lipase from Yarrowia lipolytica (YLLIP2), and a known sn-2 lipase, Candida antarctica lipase A (CALA) were used to validate this method. TLC analysis of lipolysis products showed that the lipases tested were able to hydrolyze the sn-OEO and the tung oil TAGs, but only CALA hydrolyzed the sn-2 position. The ratio of initial velocities on sn-OEO and tung oil TAGs was used to estimate the sn-2 preference of lipases. CALA was the enzyme with the highest ratio (0.22 ± 0.015), whereas HPL and YLLIP2 showed much lower ratios (0.072 ± 0.026 and 0.038 ± 0.016, respectively). This continuous sn-2 lipase assay is compatible with a high sample throughput and thus can be applied to the screening of sn-2 lipases.