Bacteria from industrial waste: potential producers of polyhydroxyalkanoates (PHAs) in Manizales, Colombia

Polymers are currently used in the industry as raw material, yet they are rapidly eliminated and largely contaminate the environment. To address this issue, there is a special interest in biodegradable polymers, namely, polyhydroxyalkanoates (PHAs), produced by microorganisms. This study identifies PHA-producing bacteria from two industrial wastewaters of Manizales, Colombia. The samples were cultured in mineral salt medium with glucose as the carbon source in the presence of Nile red stain. The fluorescent colonies were independently transferred to another medium and assessed through fluorescence microscopy with Nile blue stain. The fluorescent strains under Nile blue staining were purified in Nutrient Agar, and their morphological and microbiological characteristics were determined. The bacteria positive for red-orange fluorescence were purified in Nutrient Agar medium, and molecular analyses were performed by PCR amplification of a 650-bp fragment of the 16S ribosomal DNA gene. The bacteria were also assessed in terms of PHA production. We confirmed the identity of 12 out of 14 PHA-positive strains, which belonged to the following genera: Bacillus, Lactococcus, Citrobacter, Enterobacter, and Acinetobacter. Five of the isolates (Enterobacter cloacae, Enterobacter sp., Enterobacter ludwigii, Bacillus thuringiensis, and Bacillus safensis) are promising strains for PHA production, with production values ranging from 0.360 to 0.9960 g/L. Bacteria that produce more than 0.3 g/L are considered useful for the industrial manufacture of bioplastic. We recommend performing large-scale studies on these strains to assess their use for the industrial production of biopolymers, allowing to generate high-impact bioconversion processes of industrial interest.