Simple stain-free screening method for pectinolytic microorganisms under alkalophilic conditions

Abstract

Objectives: To develop a simple pectin-degrading microorganism screening method.

Results: We developed a method utilizing the phenomenon whereby cooling an alkaline agar medium containing pectin causes the agar to become cloudy. This highly simplified method involves culturing the microorganisms on pectin-containing agar medium until colony formation is observed, and subsequent overnight cooling of the agar medium to 4 °C. Using this simple procedure, we successfully identified pectin-degrading microorganisms by observing colonies with halos on the clouded agar medium. We used alkaline pectinase and Bacillus halodurans, which is known to secrete alkaline pectinase, to establish the screening method. We demonstrated the screening of pectin-degrading microorganisms using the developed method and successfully isolated pectin-degrading microorganisms (Paenibacillus sp., Bacillus clausii, and Bacillus halodurans) from a soil sample.

Conclusions: The developed method is useful for identifying pectin-degrading microorganisms.

Keywords: Alkaline pectinases; Alkalophilic bacteria; Halo assay; Non-staining; Pectinolysis; Screening.