Evaluation of plasmid-mediated decolourisation of vat dyes by indigenous bacterial isolates from local textile factories in Itoku, Abeokuta

Abstract

Effective mitigation and control of environmental damage brought on by the improper disposal of textiles industrial effluent is particularly noteworthy. Biodegradation of textile wastewater is emerging as a successful, environmentally friendly, and promising strategy and microbial cells that contain plasmids have specific capabilities. The present study aimed to determine the presence or absence of plasmid-mediated indigenous isolates in the decolourisation of vat dyes. Studies were carried out with four bacterial isolates, namely: <em>Klebsiella oxytoca,</em> <em>Bacillus firmus, Staphylococcus aureus </em>as well as<em> Bacillus</em> <em>macerans </em>using 100 mg/L of vat dyes (vat red 15, vat brown 1 and vat black 27) in mineral salt medium for 5 days. Bacterial isolates were cured of their plasmid using sodium dodecylsulphate (0.06 g, 0.08 g, 0.11 g, 0.22 g, 5 g and 10 g) and 10 µL of ethidium bromide (EtBr) at 40 ᴼC and decolourisation was rebated. The results showed that the plasmid weight of the bacterial isolates were 1500 bps and their plasmids were not cured until when sodium dodecylsulphate and ethidium bromide were combined. High decolourisation occurred before plasmid curing with the highest value of 96% by <em>Bacillus macerans</em> for vat black 27 dye and vat red dye decolorization activity of <em>Staphylococcus aureus</em> was the lowest at 40%. After plasmid curing, the decolourisation activity of the isolate reduced tremendously to 7% by <em>Klebsiella oxytoca</em>. The result obtained revealed the decolourisation abilities of selected isolates and also showed that decolourisation of vat dye is plasmid-mediated revealing that the gene encoding for dye decolourisation is harbored in the plasmid.