Evaluation of pullulan production by a newly isolated Micrococcus luteus

Pullulan is one of the most essential exopolysachharides (EPS) of α(Glucan) units in which most commonly α(1→4) linkage predominate. The Aureobasidium pullulans is the key microorganism for pullulan production. A major problem with Aureobasidium pullulans is coproduction of melanin along with pullulan. In this study, we looked for a novel strain having potential to produce pullulan without producing melanin and to evaluate various process parameters for its production. A total of 20 isolates were obtained from the soil sample but out of these only one strain that produced a significant amount of pullulan (71.39 mg/mL). This strain was identified as Micrococcus luteus (GenBank accession no KX261689) based upon the 16S rRNA sequencing. The characterization of pullulan was done with Enzymatic (Pullulanase) hydrolysis study and FTIR analysis. More than 85% hydrolysis of pullulan by pullulanase enzyme had also indicated the presence of α(1→6) and α(1→4) linkages in the structure of pullulan. Various evaluated values of different parameters for production of pullulan were found to be pH: 6.0, Temperature:35˚C, rpm: 250, Incubation time: 5 days. A Central Composite Design (CCD) was implemented in which peptone showed more effect than other factors in pullulan elaboration.