Bioprospecting and Molecular Identification of Used Transformer Oil-Degrading Bacteria for Bioplastics Production.

One of the major impediments to the commercialization of biodegradable plastic is the high cost of substrate. Consequently, there is a continuous search for effective microorganisms and cheaper carbon substrates to reduce the high production cost. In this study, waste transformer oil-degrading bacteria were isolated from soil, wastewater, and sediment samples, using a mineral salt medium (MSM) supplemented with 1% waste transformer oil as the sole carbon source. The isolates were screened for polyhydroxyalkanoates (PHA) production using Nile red staining and fluorescence microscopy. PHA granules accumulation was confirmed using transmission electron microscopy. Oil degradation analysis was accomplished using solvent extraction and gravimetric methods whereas, the bacteria were identified using 16S DNA sequence homology. A total of 62 transformer oil-degrading bacteria were isolated, out of which 16 (26%) showed positive results for Nile red fluorescence microscopy. The identified organisms belong to four different taxonomic genera of Acinetobacter, Bacillus, Proteus, and Serratia. The percentage of oil degradation observed among the different isolates ranged between 19.58% and 57.51%. Analysis of the PHA extracted from the selected isolate revealed the presence of medium chain length polyhydroxyalkanoates (mcl-PHA). The findings of this work have further highlighted the diversity of the bacteria capable of utilizing waste streams such as waste transformer oil. Consequently, the isolates can be explored as agents of converting waste transformer oil into bioplastics.

Bioconversion of Used Transformer Oil into Polyhydroxyalkanoates by Acinetobacter sp. Strain AAAID-1.5.

In this research, the utilisation of used transformer oil (UTO) as carbon feedstock for the production of polyhydroxyalkanoate (PHA) was targeted; with a view to reducing the environmental challenges associated with the disposal of the used oil and provision of an alternative to non-biodegradable synthetic plastic. Acinetobacter sp. strain AAAID-1.5 is a PHA-producing bacterium recently isolated from a soil sample collected in Penang, Malaysia. The PHA-producing capability of this bacterium was assessed through laboratory experiments in a shake flask biosynthesis under controlled culture conditions. The effect of some biosynthesis factors on growth and polyhydroxyalkanoate (PHA) accumulation was also investigated, the structural composition of the PHA produced by the organism was established, and the characteristics of the polymer were determined using standard analytical methods. The results indicated that the bacteria could effectively utilise UTO and produce PHA up to 34% of its cell dry weight. Analysis of the effect of some biosynthesis factors revealed that the concentration of carbon substrate, incubation time, the concentration of yeast extract and utilisation of additional carbon substrates could influence the growth and polymer accumulation in the test organism. Manipulation of culture conditions resulted in an enhanced accumulation of the PHA. The data obtained from GC-MS and NMR analyses indicated that the PHA produced might have been composed of 3-hydroxyoctadecanoate and 3-hydroxyhexadecanoate as the major monomers. The physicochemical analysis of a sample of the polymer revealed an amorphous elastomer with average molecular weight and polydispersity index (PDI) of 110 kDa and 2.01, respectively. The melting and thermal degradation temperatures were 88 °C and 268 °C, respectively. The findings of this work indicated that used transformer oil could be used as an alternative carbon substrate for PHA biosynthesis. Also, Acinetobacter sp. strain AAAID-1.5 could serve as an effective agent in the bioconversion of waste oils, especially UTO, to produce biodegradable plastics. These may undoubtedly provide a foundation for further exploration of UTO as an alternative carbon substrate in the biosynthesis of specific polyhydroxyalkanoates.

Genome-scale metabolic models as platforms for identification of novel genes as antimicrobial drug targets.

The growing number of multidrug-resistant pathogenic bacteria is becoming a world leading challenge for the scientific community and for public health. However, advances in high-throughput technologies and whole-genome sequencing of bacterial pathogens make the construction of bacterial genome-scale metabolic models (GEMs) increasingly realistic. The use of GEMs as an alternative platforms will expedite identification of novel unconditionally essential genes and enzymes of target organisms with existing and forthcoming GEMs. This approach will follow the existing protocol for construction of high-quality GEMs, which could ultimately reduce the time, cost and labor-intensive processes involved in identification of novel antimicrobial drug targets in drug discovery pipelines. We discuss the current impact of existing GEMs of selected multidrug-resistant pathogenic bacteria for identification of novel antimicrobial drug targets and the challenges of closing the gap between genome-scale metabolic modeling and conventional experimental trial-and-error approaches in drug discovery pipelines.