Identification and Biotyping Enterotoxigenic Escherichia coli Strains from Tuna Loins and Flakes Produced in Côte d’Ivoire

Aims: The study aims to explore the enterotoxigenic Escherichia coli (ETEC) strains isolated from tuna loins and flakes produced in Côte d’Ivoire and identify their biotypes. Study Design: Tuna loins and flakes were obtained from two industries located in Abidjan. Samples of about 500 g frozen tuna were collected in a polyethylene bag and labelled. Samples were stored in an ice box and sent to the laboratory for determination of virulence genes.. Place and Duration of Study: The study was conducted at Central Laboratory for Food Hygiene and Agribusiness, LANADA, Abidjan and Laboratory of Biotechnology and Food Microbiology, Department of Food Science and Technology, University of Nangui Abrogoua Abidjan, Côte d’Ivoire during June 2013 to September 2013. Methodology: 460 Escherichia coli strains isolates were analysed for the presence of diarrhoea-associated genes (elt and est) by multiplex PCR using specific primers and for the biotyping of ETEC strains based on the characters highlighted with the API 20E gallery. Results: Forty-four isolates (21 from tuna loins and 23 from tuna flakes) were identified for ETEC, including 22 positive for elt, 8 positive for est and 14 positive for both elt and est. Four biotypes (biotype 1, 2, 3 and 4) were observed in this study. Biotype 2 [LDC (-), ODC (-)] was the most prevalent in the strains with frequencies of 56.8% followed by biotype 1 (31.8%), biotype 3 (6.8%) and biotype 4 (4.5%). Conclusion: This study revealed the presence of different biotypes diarrhoeagenic E. coli (ETEC) and potential public health risks if tuna products are not properly cooked.

Electrostatic and Water Content Effects on Yarrowia lipolytica Lipase Immobilization by Adsorption.

Aims: In the present investigation, an attempt has been made to explain lipase immobilization by adsorption on three minerals matrixes, i.e. Celite 545, Silica gel (60G) and Avicel (PH 101). Study Design: immobilization by absorption on minerals matrixes, water content by volumetric karl Fischer titration and surface potentials using a particle charge detector Mutek PCD 03 were used. Place and Duration of Study: Walloon Centre of Industrial Biology (CWBI) Unit of Bio- Industries, University of Liege, Gembloux Agro-Bio Tech, Passage des Deportes 2, B- 5030 Gembloux, Belgium between Jun 2012 and jun 2013. Methodology: A methodical order was developed whereby the influences of water content, surface potentials and pH, on immobilization by adsorption were explored. Adsorbed YLL was used to understand an interesterification reaction between rapeseed oil and milk fat in comparison with a commercial silica-granulated Thermomyces lanuginosus lipase (Lipozyme TL IM). Results: Maximum immobilization yield was obtained with Celite (70%) and the lowest with silica gel (29%). Total water content of free and immobilized lipase was determined by volumetric Karl Fischer titration. The water content of Silica gel was higher than the one of other supports. Water content of silica gel could prevent the enzyme fixation. These results could be explained by the adsorption being governed mainly by electrostatic interactions between the enzyme and matrix. This hypothesis was further reinforced by measurements of electrical potential. They showed a lowest negative potential of Silica gel after enzyme adsorption in comparison to Celite. Conclusion: From these results celite was designated as an efficient matrix to immobilize Yarrowia lipolytica lipase (YLL) by adsorption. This performed system was used to realize an interesterification reaction between rapeseed oil and milk fat in comparison with a commercial silica-granulated Thermomyces lanuginosus lipase (Lipozyme TL IM).

Assessing the Microbiological Level and the Incidence of Water-soaking on the Proximate Composition of two Cultivars of Cowpea (Vigna unguiculata L.) Grains Grown in Côte d’Ivoire.

Aims: This study was undertaken to assess the influence of seed treatment (soaking in water) on nutritional and microbiological composition of two cowpea cultivars. Place and Duration of Study: Laboratory of Food Biochemistry and Tropical Products Technology, and the laboratory of Biotechnology and Food Microbiology, University of Nangui Abrogoua, Abidjan, between October 2010 and December 2011. Study Design: Method based on AOAC tests and AFNOR for microbiological analysis. A two-way analysis of variance and t-test were used. Methodology: The proximate composition of soaked and non soaked cowpea grains was determined and microbiological (bacteriological and mycological) analysis of these grains was also performed. Results: The major components were 28% and 26.25% protein, 48.35% and 47.99% carbohydrate, 41.66% and 40.05% starch for the RC (red cultivar) and WC (white cultivar) respectively. Lipids are less represented in the 2 cultivars (2.5%). There were significant reductions in the contents of the major components as a result of the treatment. Plain water soaking brought about a significant decrease in the proximate composition causing a mean reduction of 3.14% and 10.02% protein, 28.23% and 29.30% carbohydrate, 29.47% and 28.94% starch, 18.80% and 22.02 % energy for the RC and WC respectively. The mean decrease for mineral was 23.13% and 47.66% iron, 2.32% and 8.15% calcium, 9.30% and 2.10% phosphorus for the RC and WC respectively. In general the highest reduction was observed in the WC variety. Mean count (Log10 cfu/g) of total aerobic miroflora, coliforms, mould and yeast were 6.29 and 6.43; 2.04 and 2.58; 4.41 and 4.78 for the RC and WC respectively. Five genera of mould were isolated: Aspergillus, Mucor, Penicillium, Botrytis and Geotrichum. The predominant fungi belonged to Aspergillus genus. Conclusion: The cultivar types of cowpea and the preparation methods could affect the nutrient availability of this product. Cold water soaking has a great influence on the properties of cowpea grains.