Isolation and identification of bacteria and fungi growing spontaneously on polyhydroxyalkanoate pellets recovered by a new biological process

Aims: The study was carried out to isolate and identify the spontaneously growing populations of bacteria and fungi on the surface of biologically recovered polyhydroxyalkanoate (PHA) copolymer, poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) [P(3HB-co-3HHx)]. Methodology and results: Large-scale PHA biosynthesis was carried out using 300 L fermenter and a biological methodology developed in our laboratory was utilized for PHA recovery. Using standard microbiological and molecular biology techniques the naturally growing microbial populations on the surface of biologically recovered PHA were identified. Scanning electron microscopy (SEM) analysis showed that the identified bacterial (Bacillus cereus and Burkholderia cepacia) and fungal isolates (Aspergillus niger, Byssochlamys nivea, Penicillium citrinum and Penicillium griseofulvum) were able to grow on and degrade the P(3HB-co-3HHx) copolymer. Conclusion, significance and impact of study: This is the first report on biologically recovered PHA pellet addressing the occurrence of microorganisms that grew spontaneously on it during storage under laboratory conditions. Fungi appeared to be dominant over bacteria in their ability to colonize the biologically recovered PHA.