Abstract
Background
Brevibacillus
, a spore-forming and resilient bacterium, thrives in diverse environments. This study investigated the plastic-degrading potential of three
Brevibacillus spp.
(SM1, SM2, and SM3) isolated from landfill soil near Dhaka, Bangladesh.
Method
The isolated strains were first characterized based on their optimal growth conditions, morphology, and biochemical properties. 16S rRNA gene sequencing and phylogenetic analysis were conducted to identify the isolates.
Results
All three isolates exhibited optimal growth at an alkaline pH of 8-8.5 and tolerated extreme conditions up to pH 11.5 and temperature 55 °C. SM1 and SM3 grew best at 30-37 °C, while SM2 favored 40-45 °C. Microscopy confirmed all isolates as Gram-positive, rod-shaped, and motile. Biochemical tests yielded positive results for oxidase, catalase, and citrate in all strains. SM1 exhibited the highest lipase activity, while esterase activity was higher in SM2 and SM3. A halo around SM2 on polyethylene glycol plates indicated potential degradation. All strains demonstrated the ability to utilize PET, LDPE, and LLDPE as sole carbon sources in degradation assays. The weight-loss analysis indicated greater LLDPE degradation efficiency over time in SM1 and SM3 compared to SM2. The DCPIP assay confirmed degradation of PET and LDPE by SM2. Molecular identification (16S rRNA and BLASTn) revealed 97% similarity to
Brevibacillus
species (
B. parabrevis
,
B. reuszeri
, and
B. brevis
). MSA and phylogenetic analyses confirmed their taxonomic placement within the
Brevibacillus
genus.
Conclusion
These findings highlight the potential of wild-type
Brevibacillus spp
. isolated from Bangladeshi landfill soil for application in plastic bioremediation.