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

Abstract

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

“…Furthermore, the data obtained from the GC-MS and NMR analyses of the synthesised polymer revealed that the PHA might have been composed of 3HHD and 3HOD as the major monomer constituents. This is comparable with a similar finding extensively described elsewhere [ 32 ]. In Table 6 , the molecular weight and thermal properties of the polymer produced by Acinetobacter sp.…”

“…This isolate was found to be a Gram-negative coccobacillus and designated as Acinetobacter sp. strain AAAID-1.5 with gene accession number MZ411700 [ 32 ]. The organism was used in the PHA production in shake flasks via a batch process biosynthesis with UTO as the sole carbon source.…”

“…5°8′57‴ Lon. 100°24′38‴) [ 32 ]. The mineral salt medium (MSM) used for enrichment cultivation contains gram per litre of K 2 HPO 4 (5.8); KH 2 PO 4 (3.7); (NH 4 ) 2 SO 4 (1.1); MgSO 4 ·7H 2 O (0.2); bacteriological agar (15).…”

Genotypic and Phenotypic Detection of Polyhydroxyalkanoate Production in Bacterial Isolates from Food

“…The molecular detection and subsequent phenotypic verification of the production of PHA can lead to the understanding of the biosynthetic pathways and thus to the prediction of the appropriate substrate and the resulting type of PHA formed. As a result, new producing strains may be discovered presenting a cheaper and more available substrate, leading to lower production costs of PHAs [ 10 , 30 ].…”

“…The production of P(3HB) homopolymer by Bacillus thuringiensis and Bacillus cereus from glucose was demonstrated in a study by Ray and Kalia [ 35 ]. The ability to use inexpensive substrates from waste transformer oil, waste-derived volatile fatty acids, and other types of waste were reported [ 30 , 36 ]. Priestia megaterium was identified among the isolates which produced PHA from sugars and propionic acid.…”