Pectinase from a Fish Gut Bacterium, Aeromonas guangheii (SS6): Production, Cloning and Characterization

During the present research, 11 gut bacteria were isolated from the freshwater fish, Systomus sarana (General name: olive barb) and upon screening, the strains produced extracellular pectinase enzyme. Among them, the SS6 strain was found to produce a high quantity of 208.731 U/ml pectinase and through molecular characterization the SS6 strain was identified as Aeromonas guangheii. During the culture of SS6 strain, a set of parameters were optimized through the response surface methodology with a Box-Behnken design, for the production of the enzyme. The optimal conditions were found to be 2.11% of maltose, 2.20% of yeast extract, 6.5 of pH, and a temperature of 27.3 °C at 32-h incubation. Under the above conditions, the activity of pectinase production was enhanced to 371 U/ml. The purified pectinase's molecular weight was determined to be ~ 50 kDa (by 10% 2-D PAGE). Totally, nine peptides were identified from the purified pectinase enzyme through the MALDI-TOF-MS analysis and MASCOT tool was used to get the mass spectrum of the peak at 2211 of peptide that indicated the reference pectinase protein. The referenced gene primer (pectate lyases) was PCR amplified and its nucleotide sequence was analyzed. The exo-pelA gene was cloned in pREST vector, which was found to be over expressed in Escherichia coli BL21. The ORF encoded for a mature protein comprising of 425 amino acids (1236 nucleotides) with a predicted molecular weight of ~ 48.7 kDa. The present findings underline the potential of the fish-gut microbes as a source of biotechnologically important enzymes.