Optimisation of Some Conditions for the Biodegradation of Low-Density Polyethylene Strips by Fungi Isolated from Parts of North Central Nigeria

Some optimum conditions (Incubation time, pH and Temperature) were studied for selected fungal isolates – Aspergillus flavus, Aspergillus niger, Fusarium chlamydosporium, Trichoderma sp. Mucour indicus, Rhizopus miehei, Basidobolus ranarum, and Microsporum nanum, to biodegrade low-density polyethylene (LDPE) waste by using Mineral Salts Medium (MSM) containing 0.500g LDPE strips (1cm by 5cm each) using changes in pH of the media and weight loss of the strips as indicators for ability of these microorganisms to degrade LDPE. The results revealed that four of the eight fungal isolates, Aspergillus flavus, Aspergillus niger, Fusarium chlamydosporium and Trichoderma sp. showed high ability to degrade the LDPE strips after 8 weeks of incubation in Mineral Salts Medium at pH7.05 and 30oC. There was noticeable variation in pH of the media with time of incubation with the highest change recorded for Aspergillus flavus (3.00±0.01), Aspergillus niger (3.02±0.01) and Rhizopus miehei (3.10±0.01) when compared with the control (without fungi) which remained at PH 7.05±0.02 during the 8-week incubation period. The weight loss of the LDPE recorded for Aspergillus flavus was 19.40±0.14 %, Aspergillus niger 19.40±0.18%, Fusarium chlamydosporium, 12.60±0.10% and 10.60±0.02% for Trichoderma sp. respectively. The weight loss of the LDPE strips was time dependent with the highest weight loss recorded after 8 weeks for all isolates. The optimum pH of 7.5 was recorded for LDPE degradation by Aspergillus flavus, Aspergillus niger, Fusarium chlamydosporium and Basidobolus ranarum while optimum pH of 6.5 was recorded for Trichoderma sp., Mucour indicus, Rhizopus miehei and Microsporum nanum. All the fungal isolates showed optimum LDPE degradation activity at 34oC except Fusarium chlamydosporium, Trichoderma sp., Mucour indicus and Rhizopus miehei which optimized activity at 32oC.