الفهرس 
literature review
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Abstract
Pectins are the most structurally complex polysaccharides; mainly occur in plant cell walls; especially in the middle lamella of the primary cell wall of higher plants. Pectins contribute to many biological and physiological functions; especially during abscission and growth as they determine the size, shape of cells and consequently the integrity and rigidity of plant tissues.
Pectins are subjected to many pectinolytic enzymes of plant and microbial origin. These enzymes are composed of large number of different enzymes collectively called pectinases.
One hundred isolates of different bacteria and fungi had a pectinolytic activity. These isolates were used as representatives of the microbial flora of rotten fruits, vegetables and seeds. Pectinolytic activity was followed up resulted in selection of 21 isolates with high hydrolyses activity.
Characterization of pectinases secreted by 21 isolates was carried out through determination of the following enzymes: polygalacturonase (PG); polygalacturonase lyases (PGL); polymethylgalacturonase (PMG); polymethylgalacturonase lyase (PMGL) and pectinoesterase (PE). The obtained results showed that isolates No. 100, 98, and 94 were higher for both PG and PMG producers while isolates No. 97, 60 and 19, 38 were best producers of PG and PMG respectively.
These isolates were species of Aspergillus and were identified as follows:
• Three isolates (No. 19, 97 and 98) belong to Aspergillus fumigatus.
• Three isolates (No. 38, 94 and 100) belong to Aspergillus niger.
• One isolate (No. 60) belongs to Aspergillus carbonahus,