Biochemical Characterization of Phenylacetaldehyde Dehydrogenases from Styrene-degrading Soil Bacteria

Biotechnological Plastic Degradation and Valorization Using Systems Metabolic Engineering

Various kinds of plastics have been developed over the past century, vastly improving the quality of life. However, the indiscriminate production and irresponsible management of plastics have led to the accumulation of plastic waste, emerging as a pressing environmental concern. To establish a clean and sustainable plastic economy, plastic recycling becomes imperative to mitigate resource depletion and replace non-eco-friendly processes, such as incineration. Although chemical and mechanical recycling technologies exist, the prevalence of composite plastics in product manufacturing complicates recycling efforts. In recent years, the biodegradation of plastics using enzymes and microorganisms has been reported, opening a new possibility for biotechnological plastic degradation and bio-upcycling. This review provides an overview of microbial strains capable of degrading various plastics, highlighting key enzymes and their role. In addition, recent advances in plastic waste valorization technology based on systems metabolic engineering are explored in detail. Finally, future perspectives on systems metabolic engineering strategies to develop a circular plastic bioeconomy are discussed.

Whole Genome Analysis and Assessment of the Metabolic Potential of Gordonia rubripertincta Strain 112, a Degrader of Aromatic and Aliphatic Compounds

The application of Gordonia strains in biotechnologies of environmental purification as degraders of pollutants of different chemical structures is an interesting research topic. The strain Gordonia rubripertincta 112 (IEGM112) is capable of utilizing diesel fuel, alkanes, and aromatic compounds. The aim of this work was to study the potential of G. rubripertincta 112 as a degrader of aromatic and aliphatic compounds and analyze its complete genome in comparison with other known G. rubripertincta strains. The genome had a total length of 5.28 Mb and contained 4861 genes in total, of which 4799 were coding sequences (CDS). The genome contained 62 RNA genes in total, of which 50 were tRNAs, three were ncRNAs, and nine were rRNAs. The strain bears plasmid elements with a total length of 189,570 nucleotides (plasmid p1517). The strain can utilize 10.79 ± 1.17% of hexadecane and 16.14 ± 0.16% of decane over 3 days of cultivation. In the genome of the strain, we have found metabolic pathways of alkane (cytochrome P450 hydroxylases) and catechol (ortho- and meta-pathways) degradation. These results will help us to further approach the fundamental study of the processes occurring in the strain cells and to enrich our knowledge of the catabolic capabilities of G. rubripertincta.

Study of ALDH from Thermus thermophilus-Expression, Purification and Characterisation of the Non-Substrate Specific, Thermophilic Enzyme Displaying Both Dehydrogenase and Esterase Activity

Aldehyde dehydrogenases (ALDH), found in all kingdoms of life, form a superfamily of enzymes that primarily catalyse the oxidation of aldehydes to form carboxylic acid products, while utilising the cofactor NAD(P)⁺. Some superfamily members can also act as esterases using p-nitrophenyl esters as substrates. The ALDH_Tt from Thermus thermophilus was recombinantly expressed in E. coli and purified to obtain high yields (approximately 15–20 mg/L) and purity utilising an efficient heat treatment step coupled with IMAC and gel filtration chromatography. The use of the heat treatment step proved critical, in its absence decreased yield of 40% was observed. Characterisation of the thermophilic ALDH_Tt led to optimum enzymatic working conditions of 50 °C, and a pH of 8. ALDH_Tt possesses dual enzymatic activity, with the ability to act as a dehydrogenase and an esterase. ALDH_Tt possesses broad substrate specificity, displaying activity for a range of aldehydes, most notably hexanal and the synthetic dialdehyde, terephthalaldehyde. Interestingly, para-substituted benzaldehydes could be processed efficiently, but ortho-substitution resulted in no catalytic activity. Similarly, ALDH_Tt displayed activity for two different esterase substrates, p-nitrophenyl acetate and p-nitrophenyl butyrate, but with activities of 22.9% and 8.9%, respectively, compared to the activity towards hexanal.