1. Anne Richards, Cara Broshkevitch, Ong Kim Yao, and Poh Yong Rui

2.  HDPE plastic: used in food packaging, plastic bags, plastic bottles, recycled plastic lumber, toiletry and liquid containers, outdoor furniture, and piping  Takes over 100 years to degrade in a landfill-discarded plastics filling up landfills (Sivan, 2011)  Detrimental environmental effects:  Water and air cannot enter soil – deplete underground water resource  Disrupts degradation of other substances  In the ocean, plastic chokes and entangles marine life

3.  Other ways of disposal can not be used:  Burning plastics at high temperatures produces toxic irritants that are human carcinogens  Past research: biodegradation with bacteria or fungi, UV radiation, and thermal radiation have been separately investigated  All three organisms have been shown to degrade polyethylene plastic separately

4. Academy of Science Hypothesis: The following factors affect the rate of biodegradation of HDPE plastic mass:  Ratios of different microorganisms  P. Chrysosporium fungus  P. Putida bacteria  S. Macrogoltabidus bacteria Hwa Chong Institution Hypothesis: The following factors affect the rate of biodegradation of HDPE plastic mass:  Environmental conditions for biodegradation  Exposure time to UV radiation

5. Academy of Science  Independent variables  Ratios of P. chrysosporium fungus, P. putida bacteria, and S. macrogoltabidus bacteria  Dependent variable  Percent change in dry mass of the HDPE plastic samples  Amount of CO 2 gas present Hwa Chong Institution  Independent variables  Environmental conditions for biodegradation  Exposure time to UV radiation  Dependent variables  Percentage change in dry mass of HDPE samples  Amount of CO 2 gas present  Temperature of contents of flask  Cell density of bacterial cultures

6. Academy of Science Culture Bacteria and Fungi Pre-treat Plastic Expose Plastic to Individual Microorganisms Expose Plastic to different Ratios of 3 Microorganisms Measure Dependent Variables Hwa Chong Institution Culture Bacteria Prepare Soil Conditions Pre-treat Plastic Expose Plastic to Microorganisms Measure Dependent Variables

7. Bacteria will be cultured in culture test tubes with nutrient broth Fungi will be cultured in Petri dishes in potato dextrose agar

8. Erlenmeyer flask with minimal media Erlenmeyer flask with loamy soil and distilled water

9. HDPE Plastic Grocery Bags Exposed to 365nm UV radiation for 96 hours Cut into one gram pieces Exposed to thermal radiation in the oven at 115°C for 48 hours Exposed to 365nm UV radiation for 72, 96, 120 hours AOSAOS HCIHCI Cut into one gram pieces HDPE Plastic Grocery Bags Exposed to thermal radiation in the oven at 115°C for 48 hours

10. Academy of Science Expose plastic to:  Individual microorganisms  P. putida  S. macrogoltabidus  P. chrysosporium  Different ratios of the three microorganisms Hwa Chong Institution Expose plastic to:  P. putida in:  Minimal Media  Loamy soil + Distilled water

11. Will be used to measure:  Percentage change in dry mass of HDPE samples  Amount of CO 2 gas present  Temperature of contents of flask  Cell density of bacterial cultures Thermometer CO 2 Probe Analytical Balance Spectrophotometer AOSAOS HCIHCI

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