Ibrahim N. Ibrahim’s scientific contributions

Out of 70 fungal isolates recovered from soil, wall paints (Latex), and pieces of plastic debris from different habitats in Jordan and plastic shields of street light posts on campus, 35 isolates showed varied potential to degrade polyester-polyurethane (PS-PUR). Six of these isolates (Fusarium solani, Alternaria solani, Spicaria spp., Aspergillus fumigatus, Aspergillus terreus, and Aspergillus flavus) were selected on the basis of their growth rates on basal salt media amended with PS-PUR as the sole source of carbon. Isolates were further evaluated utilizing 3 different methods: 1) direct plating, 2) clear zone in a 2-layered agar media, and 3) liquid shaking culture. These isolates caused significant weight loss in the PS-PUR blocks in the shaken cultures, reaching up to 100% in case of the isolate Fusarium solani. The petri dish test method revealed a maximum degradation activity achieved by the isolate Aspergillus flavus, which caused 94% loss in weight of PS-PUR pieces. However, only 4 isolates (Fusarium solani, Spicaria spp., Alternaria solani, and Aspergillus flavus) yielded positive results of biodegradation, indicated by clear zones created due to PS-PUR hydrolysis in 2-layered agar culture plate media. Out of the 6 fungal isolates reported here, 2 novel organisms have not been previously reported, Alternaria solani and Spicaria spp. Overall, these findings helped identify predominant as well as novel fungi in Jordanian habitats that play a key role in PS-PUR degradation.

Alternaria solani isolate number Ss1-3, isolated from soil sample from northern Jordan was found to be able to utilize the polyester-polyurethane (PS-PUR) as sole source of carbon and nitrogen. After three weeks of incubation at pH7 and30 °C, A. solani caused 65.8% loss in weight, 24.7% reduction in tensile strength at break, and 28.2% decrease in percentage elongation at break, of PS-PUR substrate blocks. There was conspicuous microscopic cracking of the PS-PUR surface. Penetrating fungal hyphae through the PS-PUR blocks was envisaged, initially in the reduction in the number of -CH2- groups and increases in the number of -OH groups of PS-PUR, and as ascertained by Fourier transform-Infrared (FT-IR) spectrophotometer. The detection of acid and amine fractions by thin-layer chromatography (TLC) in the purified culture filtrate (PCF), which is comparable to that in the acid hydrolyzed PS-PUR, was attributed to the biological hydrolysis, by the fungus, of diisocyanate segment in this polymer. Adipic acid, diethylene glycol, and trimethylolpropane were probably the main degradation products released from the polyester segment in the PCF and detected by high performance liquid chromatography (HPLC) when PS-PUR was utilized as a source of carbon. This is further supported by protease activity of A. solani.