SCREENING AND DNA IDENTIFICATION OF THREE NEWLY ISOLATED BACTERIAL STRAINS FROM VARIOUS ENVIRONMENTAL BIOTOPES IN ALGERIA, PRODUCING EXTRACELLULAR POLYSACCHARIDES (EPSs)

Exopolysaccharides (EPSs) of microbial origin exhibit substantial advantages compared to their synthetic equivalents, due to their lower toxicity, higher selectivity, and better degradability. In this context, this study aimed to characterize three newly isolated strains producing extracellular polysaccharides, which are indigenous to different biotopes in Algeria. The EPSs-producing bacteria were preliminarily screened according to the red ruthenium coloration. The production of EPSs was evaluated by measured viscosities of the enriched biomass in HJL broth medium and by studying the effect of pH and temperature. Phylogenetic analysis of the three best performing strains, based on partial sequences of their PCR amplified 16S rRNA genes was used to distinguish the individual isolates. As a result, three genetically distinct strains designated LGM-TAM3, LGM-TAM4, and LGM-TAM5 were found to belong to the genera Serratia and Aeromonas. Specifically, these strains were found closely related to Serratia marcescens subsp. Sakuensis, Aeromonas media, and Serratia nematodiphila with16S rRNA similarities to type strains, of 86.20, 99.70, and 99.85%, respectively. Furthermore, the best EPSs production was recorded by the strain LGM-TAM5 at pH 7.5 and 30 °C with a viscosity value of 1289 cP. Based on FTIR spectroscopic analyses, functional groups of polysaccharides were identified in the crude EPSs of each strain, which mainly include a hydroxyl group (-OH stretching), (C-H) of aliphatic groups, and carboxylate groups  (-COO-). These interesting results are encouraging as the study's first phase and will be supported by additional research to better understand the biological fonctions and the potential uses of the investigated EPSs.