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Articles by A. Cheikhyoussef
Total Records ( 2 ) for A. Cheikhyoussef
  A. Cheikhyoussef , N. Pogori and H. Zhang
  The antimicrobial effects of the supernatants obtained from four strains of bifidobacteria were tested against two types of indicator strains, Bacillus cereus and three strains of Escherichia coli. E. coli AS 1.543 was the most sensitive strain among the E. coli strains whereby B. bifidum showed the highest antimicrobial activity against indicator strains followed by B. infantis then B. longum and finally B. adolescentis. There was a significant reduction in the growth of the indicator strains, whereby all E. coli strains were inhibited more than 75% of their log CFU in monoculture, of which B. infantis reduced 95% of E. coli AS 1.543. On the other hand only more than 60% of the log CFU of B. cereus was reduced by all bifidobacterial supernatants in particular B. longum (75%). It was observed that substances or factors other than organic acids may contribute to the antimicrobial activity of the supernatants (CFS) from the bifidobacteria studied. Neutralization of the CFS from B. adolescentis and B. bifidum significantly reduced the antimicrobial activity while that from B. infantis and B. longum continued to inhibit growth of the indicator strain as observed by a clear defined zone uncharacteristic of acid production by the agar diffusion method. The inactivation of the antimicrobial activity of CFS from B. infantis and B. longum by proteolytic enzymes confirms the proteinaceous nature of the antimicrobial compound present. In addition their heat and pH stability further proves the presence of a proteinaceous antimicrobial compound which could be designated as bacteriocins or bacteriocin-like compounds.
  N. Pogori , Y. Xu and A. Cheikhyoussef
  Lipases (triacylglycerol acylhydrolases, E.C. 3.1.1.3) are a class of hydrolases that catalyze both, hydrolysis and synthesis of esters which are formed from glycerol and long-chain fatty acids. Lipases are potential enzymes which are used extensively in a wide range of industrial applications. The production, biochemical properties and application potentials of the extra-and intra-cellular lipases obtained from Rhizopus fungi have been studied by various researchers. Research efforts are being directed towards obtaining high enzyme yields of both intracellular and extracellular lipases from Rhizopus by optimizing production or through genetic engineering and in purifying these lipases to elucidate structure, properties and potential applications. Lipases from the Rhizopus genus have been found to have enantioselectivities suitable for resolution of various compounds which have potential in the synthesis of pharmaceuticals, cosmetics, agrochemicals and other products. More attention is being paid to Rhizopus lipases for their strong 1,3-position specificity making them especially suitable for lipid modifications. Rhizopus lipases either as whole cell biocatalyst or as the purified form of lipase have great potential for biodiesel production from waste oils which is an ever-expanding industrial field. Some of the purified lipases of this genus exhibit thermostability and good stability in organic solvents which therefore have a great potential in the biocatalysis industry.
 
 
 
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