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A simple, fast and ecological analytical method using a semi-automatic fat extractor and HPLC-FLD (fluorescence detection) for determination of polycyclic aromatic hydrocarbon markers i.e. benzo(a)anthracene (BaA), chrysene (Chr), benzo(a)pyrene (BaP) and benzo(b)fluoranthene (BbF) in cocoa butter has been validated. Validation's procedure performed out in concordance with French standard NF V03-110 (2010) was based on existing polycyclic aromatic hydrocarbon (PAH) determination methods in various smoked foodstuffs and edible vegetable oils. Determination of correlation coefficients for specific PAHs ranged from 0.9992 to 0.9998. Respective values of limits of detection were 0.010, 0.011, 0.033 and 0.029 μg kg−1 and those of quantification were 0.035, 0.038, 0.111 and 0.098 μg kg−1 for BaA, Chr, BbF and BaP. Both values of repeatability and intermediary precision tests coefficients of variation were less than 5%. Recovery scores of four PAH markers matched EU standard 836/2011 recommendations. Sum of four PAH markers (BaA, Chr, BbF, BaP) contents varied from 5.42 ± 0.58 to 11.37 ± 0.01 μg kg−1 whereas those of BaP was comprised between 0.26 ± 0.00 and 1.75 ± 0.13 μg kg−1 in 20 cocoa butter samples extracted from raw cocoa bean stored at Ivorian cocoa farmer levels.

The search for new sources of oil with improved characteristics has focused our attention on the characterisation of Irvingia gabonensis seed kernel oil. Physicochemical analysis have revealed the following assets: refractive index (1.42 ± 0.00), free fatty acids (2.3 ± 0.8%), peroxide value (3.33 ± 0.57 meq O2/kg), iodine value (32.43 ± 1.22 g I2/100 g), saponification value (233.75 ± 2.60 mg KOH/g), unsaponifiable matter (1.5 ± 0.02%), carotenoids (63 ± 0.01 mg β-carotene/100 g) and phospholipids (2.1 ± 0.01%). Absorbance of this oil decreased abruptly in the range of UV-B and UV-A wavelengths. Gas chromatography analysis showed that the major fatty acids were saturated, being mainly composed of lauric (C12:0, 39.35 ± 0.01%) and myristic acids (C14:0, 20.54 ± 0.01%). Nevertheless, an unusually high amount (6.44 ± 0.02%) of linolenic acid was also noted. Mass spectrometer analysis of volatile compounds highlighted the presence of various aromatic and aliphatic organic compounds. I. gabonensis seed kernel oil also showed oxidative stability at 60 °C after 12 days of storage with maximum peroxide value of 34.66 meq O2/kg. In view of these interesting characteristics, I. gabonensis seed kernel could be used as an alternative source of oil for lipid industries.

This work was carried out to determine the potential applications of Corchorus olitorius and Hibiscus sabdariffa oil seeds by investigating their physicochemical and microbiological characteristics. Physicochemical parameters of the extracted oils were respectively as follow: refractive index (1.46 and 1.45), acid value (3.74 ± 1.62 and 2.80 mg KOH/g), peroxide value (6.67 ± 0.58 and 5.33 ± 0.60 meq O 2 /kg), iodine value (132.54 ± 1.22 and 118.57 ± 1.22 g I 2 /100 g), saponification value (183.63 ± 3.24 and 189.23 ± 1.62 mg KOH/g), unsaponifiable matter (0.88 ± 0.04 and 0.85 ± 0.05 %), vitamin A (0,45 ± 0.01 and 0.60 ± 0.01 mg/g), cholesterol (0.00 mg/g) for C. olitorius and H. sabdariffa respectively . Absorbances of the two oils decreased abruptly in the range of UV-B and UV-A wavelengths. C. olitorius and H. sabdariffa seeds showed relatively high content of linolenic acid (about 29 and 37% of total fatty acids) with extremely low n-6/n-3 ratio (0.26 and 0.46). Microbiological analysis revealed that the crude extracted oilseeds were pathogenic bacteria free and the lipolytic bacteria counted belonged to Micrococcus genus. All these interesting characteristics should arouse attention for the usage of these oilseeds in food, pharmaceutical and cosmetic industries. Key words : Corchorus olitorius, Hibiscus sabdariffa , seed oils characterization, linolenic acid, lipolytic bacteria.

An extracellular α-mannosidase with unusual properties was purified from the digestive fluid of oil palm weevil (Rhynchophorus palmarum Linnaeus) larvae using ammonium sulphate saturation, size exclusion and anion-exchange chromatography. The enzyme named RpltM is thermoacidophilic, thermostable and behaves like lysosomal α-mannosidase (EC 3.2.1.24). The molecular weight, Km value, optimum reaction temperature and pH are 108-112 kDa, 0.36 mM, 65°C and 4.5, respectively. Zn2+ enhanced whereas Cu2+, Sodium dodecyl sulphate, swainsonine and 1,4-dideoxy-1,4-iminomannitol strongly inhibited its hydrolytic activity. The enzyme was stable for 25 min at 65°C and retained 70% of its initial activity after 60 min. At 70°C, around 60% of this activity was conserved after 25 min. RpltM retained more than 90% of its activity over a pH range of 4.2 to 5.0 and remained fully active in the presence of detergents such as nonidet P-40, triton X-100, polyoxyethylen-10-oleyl ether (up to 1%, w/v), dithiothreitol and β-mercaptoethanol. The stability under these conditions is also better than that reported for other insect α-mannosidases. Thus, RpltM could be used as an important bioindustrial tool for removing mannose residues from oligosaccharides.

Purpose: To investigate the seed oils of Corchorus olitorius and Hibiscus sabdariffa for their antioxidant and antimicrobial potential. Methods: The physicochemical characteristics of oil of the plant seeds were determined using standard methods while their volatile compounds were analyzed by gas chromatography coupled with mass spectrometery (GC-MS). The antioxidant activity of these oils was determined using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method, and their antimicrobial effect was determined by agar dilution method. Results: Phospholipids, carotenoids and phenols contents of the studied seed oils were approximately 2.0 %, 100 mg/100g and 6.7 mg/100g, respectively. GC-MS analysis of the volatile compounds showed the presence of various aromatic and aliphatic organic compounds while the antioxidant activity of the oils was in the range of 0 to 5 g/l, which was higher than that of ascorbic acid. The seed oils also showed antimicrobial activity against Staphylococcus aureus, Aspergillus fumigatus and Trichophyton mentagrophytes with minimal inhibitory concentrations (MIC) of 250.0 and 62.5 mg/ml for C. olitorius and H. sabdariffa seed oils, respectively. Conclusion: C. olitorius and H. sabdariffa seed oils showed pronounced antioxidant and antimicrobial activities. These characteristics should be exploited for possible applications in the food supplement, pharmaceutical and cosmetic industries.

Two biological fluids, namely hemolymph and digestive fluid from the larval stage of Rhynchophorus palmarum Linneaus, a serious pest in agroecosystem exploiting oil palm, were screened for hydrolytic activities, by the use of synthetic and natural glycoside substrates. Several exo and endoglycosidase activities were observed but, the interesting alpha-mannosidase activity (0.41 +/- 0.04 UI) had attracted our attention. So, we have previously demonstrated that this activity harbours four distinctive alpha-mannosidase isoforms named RpltM, RplM1, RplM2 and RplM3. We have extended this work to determine the ability of these enzymes to catalyze synthesis reactions. Finally, we have revealed that, alpha-mannosidases from the digestive fluid of R. palmarum larvae catalyze transmannosylation reactions. The stability of the enzymes and the optimization of the transfer product yield were studied as functions of pH, enzyme unit, starting concentration of donor or acceptor and time. It was shown that, in experimental optimum conditions, average yields of 12.34 +/- 0.75, 12.15 +/- 0.79, 5.59 +/- 0.35 and 8.43 +/- 0.50% were obtained for the alpha-mannosidases RpltM, RplM1, RplM2 and RplM3, respectively. On the basis of this work, alpha-mannosidases from the digestive fluid of Rhynchophorus palmarum larvae appear to be a valuable tool for the preparation of neoglycoconjugates.

Acid phosphatase activity was detected in peanut (Arachis hypogaea) cotyledons during germination. Four (4) to six (6) days of germination was the meantime corresponding to maximum hydrolytic activity of this enzyme. The understanding of the role of acid phosphatase activity during germination led to purify this enzyme by successive chromatography separations on DEAE-Sepharose CL-6B, Sephacryl S-100 HR and Phenyl-Sepharose HP to apparent homogeneity from germinated peanut cotyledon five days old. This enzyme designated peanut cotyledon acid phosphatase (AP) had native molecular weight of 24 kDa by gel permeation. SDS-PAGE of the purified acid phosphatase resolved a single protein band that migrated to approximately 21.5 kDa. Thus, this acid phosphatase likely functions as a monomer. The enzyme had optimum pH (5.0) and temperature (55 degrees C), and appeared to be stable in the presence of anionic, cationic and non-ionic detergents. Substrate specificity indicated that the purified acid phosphatase hydrolyzed a broad range of phosphorylated substrates. However, natural substrates such as ADP and ATP were the compounds with highest rate of hydrolysis for the enzyme. Moreover, the purified acid phosphatase exhibited phytase activity. These results showed that this enzyme played a peculiar role during germination, notably in reducing the rate of phytic acid, an antinutritional substance contained in peanut seed.

Termite workers, Macrotermes subhyalinus (Rambur), produced two cellulase-free xylanases, namely Xyl A and Xyl B. DEAE-Sepharose CL-6B, Sephacryl S-200 HR, CM-Sepharose CL-6B and Phenyl-Sepharose CL-4B chromatographies purified these enzymes. They exhibited molecular masses of 63–66.1 (Xyl A) and 60.7–62.4 (Xyl B) kDa. Both enzymes appeared to be endo-xylanases, which produced oligomers of xylose from xylan and did not hydrolyse them to xylose. They had different optimum pH (pH 4.6–5.0 for Xyl A and pH 5.0 for Xyl B) and different optimum temperatures (60 °C for Xyl A and 55 °C for Xyl B). However, they had the same pH stability (4.0–5.6). Both enzymes were stable at 50 °C for more than 4 h. At a pH ranging from 4.6–5.0 and 60 °C, Xyl A and Xyl B possessed the half-life of 115 and 60 min, respectively. The xylanase activities were stimulated by Na+, Mn2+ and dithiol-reducing agents and were sensitive to Cu2+ and detergent agents. Their enzymatic activity was slightly reduced by the presence of urea at 1% (w/v) concentration. The two enzymes could be used in the presence of organic solvents such as acetone (up to 10% v/v) without loss of activity.

The influence of 57 chemicals (mineral and organic acids, organic solvents, phenolic compounds, mineral and organic salts) on the efficiency of protein determination by the Lowry method was assessed. The study revealed the Lowry method to be unreliable in an acidic and increasing vitamin C-rich medium. For organic solvents, it is advisable to evaporate these compounds when they are used to extract proteins, prior to proteins measurement the Lowry method. The influence of phenolic compounds on the Lowry method was found to be governed by the structure of their molecules (presence of double bounds, number of OH groups, presence of methyl groups, etc.), while ammonium sulfate, which is a major agent used in the enzyme purification process, was found to result in an overestimation of the protein content. Therefore, its use for enzyme purification should be done with caution. Keywords : Lowry method, protein determination, method validation, chemical interference Biokemistri Vol. 17(2) 2005: 73-81