Project description:The use of carbon labelled PBAT units allowed us to follow biodegradation of all PBAT building blocks. The presented workflow is a novel approach to study the fundamental steps in polymer biodegradation in complex systems.
Project description:The biodegradation of polyhydroxybutyrate-co-hydroxyvalerate (PHBV) ternary biocomposites containing nature-based plasticizer acetyl tributyl citrate (ATBC), heterogeneous nucleation agents-calcium carbonate (CaCO3) and spray-dried lignin-coated cellulose nanocrystals (L-CNC)-in vermicomposting, freshwater biotope, and thermophilic composting have been studied. The degree of disintegration, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the evaluation of surface images taken by scanning electron microscopy (SEM) were conducted for the determination influence of different environments and additives on the biodegradation of PHBV. Furthermore, the method adapted from ISO 14855-1 standard was used for thermophilic composting. It is a method based on the measurement of the amount of carbon dioxide evolved during microbial degradation. The highest biodegradation rate was observed in the thermophilic condition of composting. The biodegradation level of all PHBV-based samples was, after 90 days, higher than 90%. Different mechanisms of degradation and consequently different degradation rate were evaluated in vermicomposting and freshwater biotope. The surface enzymatic degradation, observed during the vermicomposting process, showed slightly higher biodegradation potential than the hydrolytic attack of freshwater biotope. The application of ATBC plasticizers in the PHBV matrix caused an increase in biodegradation rate in all environments. However, the highest biodegradation rate was achieved for ternary PHBV biocomposites containing 10 wt. % of ATBC and 10 wt. % of CaCO3. A considerable increase in the degree of disintegration was evaluated, even in freshwater biotope. Furthermore, the slight inhibition effect of L-CNC on the biodegradation process of ternary PHBV/ATBC/L-CNC could be stated.
Project description:Polylactic acid (PLA) is a promising biodegradable material used in various fields, such as mulching films and disposable packaging materials. Biological approaches for completely degrading biodegradable polymers can provide environmentally friendly solutions. However, to our knowledge, no studies have performed transcriptome profiling to analyze PLA-degrading genes of PLA-degrading bacteria. Therefore, this study reports for the first time an RNA sequence approach for tracing genes involved in PLA biodegradation in the PLA-degrading bacterium Brevibacillus brevis. In the interpretation results of the differentially expressed genes, the hydrolase genes mhqD and nap and the serine protease gene besA were up-regulated by a fold change of 7.97, 4.89, and 4.09, respectively. This result suggests that hydrolases play a key role in PLA biodegradation by B. brevis. In addition, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that genes implicated in biofilm formation were upregulated. The biodegradation of PLA starts with bacteria attaching to the surface of PLA and forming a biofilm. Therefore, it could be confirmed that the above genes were up-regulated for access to PLA and biodegradation. Our results provide transcriptome-based insights into PLA biodegradation, which pitch a better understanding of microbial biodegradation of plastics.