A total of 101 soil samples were collected from different locations where plastic wastes were accumulated, from these samples, 75 microorganisms were isolated (30 bacteria and 45 fungi). Only 9 bacterial and 9 fungal isolates showed the ability to degrade plastic polymers under investigation (PVC, PP, HDPE and LDPE), causing zone of clearance on Bushnell Haas agar (BHA) that contained different types of plastic polymers. Twelve isolates (8 bacterial and 4 fungal) showed zone of clearance on BHA plates containing PVC polymer. Only 7 bacterial isolates showed zone of clearance on BHA plates containing PP. While, 11 isolates (6 bacterial and 5 fungal) showed zone of clearance on BHA plates containing HDPE. While, 8 isolates (5 bacterial and 3 fungal) showed zone of clearance on BHA plates containing LDPE. Plastic degrading enzymes (esterase, lipase and depolymerase) secreted by isolated microorganisms, were evaluated for their activity in the presence of the suitable type of polymer for each isolate (polymer on which the isolate showed the highest zone of clearance). It was observed that nearly most of the isolates were able to produce depolymerase enzyme with different activities except two isolates (1 bacterial and 1 fungal), seven isolates (3 bacterial and 4 fungal) were able to produce lipase enzyme and only two bacterial isolates were able to show esterase enzyme activity. So for, depolymerase enzyme activity was selected to make further investigations on it. The microorganisms which were able to produce depolymerase enzyme with accepted activity (more than 0.01 U/min/mL) were selected to be identified and tested for the effect of different temperatures and pH on its growth and depolymerase enzyme activity. The selected isolates were 4 bacterial and 4 fungal isolates. Isolates were identified using phenotypic methods and confirmed by molecular methods using 16s rRNA sequencing. Bacterial isolates were identified as two Brevibacillus borstelensis, one Achromobacter insolitus and one Brevibacillus parabrevis. While fungal isolates included three Aspergillus fumigatus and one Malassezia sp. Achromobacter insolitus and Malassezia sp. are from the newly promising microorganisms in plastic biodegradation that need more researches in the future. Depolymerase enzyme activity was tested at different temperatures to find the optimum temperature for enzyme activity. It was observed that most of the isolates showed higher enzyme activity at 50ºC except for two isolate, 1 bacterium and 1 fungus that showed better activity at 40 ºC. Changing temperature from room temperature (30 ºC) to 40 ºC, 50 ºC and 60 ºC showed statistical significant increase in depolymerase enzyme activity. In addition, the effect of different pH on depolymerase enzyme activity was evaluated. It was noticed that pH 7 was the optimum pH for 5 isolates (3 bacteria and 2 fungi), pH 6 for two bacterial isolates while pH 5 was optimum for 2 fungal isolates. Statistical analysis showed that there is no statistical significance due to changing pH of the medium compared to neutral pH (7), only pH 10 showed significant effect in lowering depolymerase enzyme activity. In addition, effect of different concentrations of EDTA (0.2, 0.4, 0.6, 0.8 and 1mM) on depolymerase enzyme activity was evaluated. Presence of EDTA showed statistically significant difference in increasing the enzyme activity, while using different concentrations of EDTA showed non- statistically significant difference from each other’s. Furthermore, the effect of different ions (1mM of Ca2+, K1+, Mg2+, Fe3+) was evaluated. The results of this experiment showed that CaCl2 enhanced the bacterial depolymerase activity, while it has no effect on fungal depolymerase activity. On the other hand, FeCl3 was able to enhance fungal depolymerase activity of three fungal isolates, while it has no effect on the bacterial isolates. However, these effects were statistically non-significant. The effect of pH and temperature on microorganism’s growth is then evaluated. Percentage of growth increase after 24 hours at different pH (from 4 to 10) was tested then each isolate was grown under its optimum pH at different temperatures (30, 40, 50 and 60°C). The results indicate that all bacterial strains grow better at pH 8 except for Brevibacillus borstelensis1 that has optimum growth at pH 9. Furthermore, optimum growth was observed at 30 ºC for Brevibacillus borstelensis1 and Achromobacter insolitus, while strains Brevibacillus parabrevis and Brevibacillus borstelensis2 grow better at 40 ºC. For fungal isolates, strains A. fumigatus1 and A. fumigatus3 grew better at alkaline pH (8-9), while Malassezia sp. and A. fumigatus2 had optimum growth at acidic pH (4). Regarding temperature, it was found that 40°C was the optimum temperature for the growth of strains A. fumigatus1, Malassezia sp. and A. fumigatus3, while strain A. fumigatus2 grew better at 30°C. In general, the optimum temperatures and pH for both the growth of fungal strain and the activity of depolymerase enzyme were different from each other. Furthermore, hydrophobicity assay for fungal isolates (as a plastic degrading factor) was performed. Hydrophobicity assay demonstrated that A. fumigatus3 has the highest hydrophobicity (82.29%) followed by Malassezia then A. fumigatus2 and A. fumigatus1 with 68.82 %, 58.12% and 41.86% hydrophobicity, respectively. For further investigation of the effect of our isolates in biodegradation, further experiments were performed on PVC strips including: weight reduction analysis and SEM analysis. Weight reduction analysis of PVC strips inoculated with bacterial isolates showed that strain Brevibacillus borstelensis1 had the highest reduction (3.03 ± 0.64%) followed by strains Brevibacillus parabrevis, Brevibacillus borstelensis2 then Achromobacter insolitus with percentages 2.58 ± 0.98, 2.41 ± 0.94 and 0.22 ± 0.16, respectively. While, experiments using fungal isolates showed that strain A. fumigatus3 had the highest reduction (2.15 ± 0.42%) followed by strains A. fumigatus2, Malassezia sp. then A. fumigatus1 with percentages 1.92 ± 0.51, 1.46 ± 0.7 and 0.718 ± 0.1, respectively. PVC strips showed weight reduction more than 1% was used for further analysis using SEM. SEM analysis of PVC strips incubated with bacterial isolates for 30 days showed that Brevibacillus strains were able to form cracks on PVC strips surfaces and erosion was visible with the best erosion observed with Brevibacillus borstelensis1 strain, which showed highest weight reduction in the previous experiment. SEM analysis of f PVC strips inoculated with fungi showed that A. fumigatus3 A. fumigatus2, and Malassezia strains were able to form cracks on surface of PVC strips and the erosion was visible with the highest erosion observed with A. fumigatus3 strain, which showed highest weight reduction in the previous experiment, while SEM-image of control PVC-strips show no-erosion on PVC-strips surface.