Mycodegradation of low-density polyethylene by Cladosporium sphaerospermum, isolated from platisphere

Plastic accumulation is a severe threat to the environment due to its resistivity to thermal, mechanical and biological processes. In recent years, microbial degradation of plastic waste disposal is of interest because of its eco-friendly nature. In this study, a total of 33 fungi were isolated from the plastisphere and out of which 28 fungal species showed halo zone of clearance in agarized LDPE media. The fungus showing highest zone of clearance was further used to evaluate its degradation potential. Based on morphological and molecular technique, the fungus was identified as Cladosporium sphaerospermum. The biodegradation of LDPE by C. sphaerospermum was evaluated by various methods. The exposure of LDPE with C. sphaerospermum resulted in weight loss (15.23%) in seven days, higher reduction rate (0.0224/day) and lower half-life (30.93 days). FTIR analysis showed changes in functional group and increased carbonyl index in LDPE treated with C. sphaerospermum. SEMimages evidenced the formation of pits, surface aberrations and grooves on the LDPE film treated with the fungus whereas the untreated control LDPE film showed no change. AFM analysis confirmed the surface changes and roughness in fungus treated LDPE film. This might be due to the extracellular lignolytic enzymes secreted by C. sphaerospermum grown on LDPE. The degradation of polyethylene by Short chain alkanes such as dodecane, hexasiloxane and silane were identified in the extract of fungus incubated with LDPE film through GC-MS analysis which might be due to the degradation of LDPE film by C. sphaerospermum. This was the first report on the LDPE degradation by C. sphaerospermum in very short duration which enables green scavenging of plastic wastes.

Biodegradation mechanisms of sulfonamides by Phanerochaete chrysosporium - Luffa fiber system revealed at the transcriptome level

The overuse of antibiotics and subsequent enrichment of antibiotic resistant microbes in the natural and built environments is a severe threat to global public health. In this study, a Phanerochaete chrysosporium fungal-luffa fiber system was found to efficiently biodegrade two sulfonamides, sulfadimethoxine (SDM) and sulfadizine (SDZ), in cow urine wastewater. Biodegradation pathways were proposed on the basis of key metabolites identified using high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (HPLC-QqTOF-MS). Transcriptomic, metabolomic, and free radical analyses were performed to explore the functional groups and detailed molecular mechanisms of SDM and SDZ degradation. A total of 27 UniGene clusters showed significant differences between luffa fiber and luffa fiber-free systems, which were significantly correlated to cellulose catabolism, carbohydrate metabolism, and oxidoreductase activity. Carbohydrate-active enzymes and oxidoreductases appear to play particularly important roles in SDM and SDZ degradation. Electron paramagnetic resonance (EPR) spectroscopy revealed the generation and evolution of OH and R during the biodegradation of SDM and SDZ, suggesting that beyond enzymatic degradation, SDM and SDZ were also transformed through a free radical pathway. Luffa fiber also acts as a co-substrate to improve the activity of enzymes for the degradation of SDM and SDZ. This research provides a potential strategy for removing SDM and SDZ from agricultural and industrial wastewater using fungal-luffa fiber systems.

Efficiency, products and mechanisms of mycodegradation

The objective of the study was to assess the applicability of the mycelium obtained from the in vitro cultures of nontoxic bracket fungus, Pleurotus eryngii, to sulfonamides mycodegradation. Samples containing one of the six selected sulfonamides, sulfanilamide derivatives, were incubated with the mycelium of P. eryngii for 7 and 14 days in vitro. Subsequently, change in the sulfonamide concentration was assessed in the samples using the UPLC-QTof. The transformation products were identified based on monoisotopic molecular mass and fragmentation spectra. The studied sulfonamides did not inhibit the growth of P. eryngii mycelium in the in vitro cultures. In addition, a considerable reduction of sulfonamide concentration was observed in all the incubated samples (from 73.7 ± 8.3% to 99.8 ± 0.3%). In the case of three sulfonamides, the reduction in concentration >90% occurred after 7 days of incubation. However, the transformation of sulfonamides was partially caused by their degradation to simpler organic compounds. After incubation, the products of condensation of sulfonamides with formyl, acyl, and sugar groups, and amino acid-derived compounds were identified in the samples. This indicated the partially reversible nature of the mycodegradation process.