Study on screening and identification of an alkaline pullulanase-producing strain and its enzymic characterization

A wild strain named M25 with alkaline pullulanase was isolated from the marine mud on a selective medium that contained pullulan as the only source of carbon.It was identified as Pseudoalteromonas sp.according to its morphological observation and 16 S rDNA sequence analysis.The highest level of pullulanase was discovered at 18 h after inoculation at 30 ℃,200 r /min.The pattern of pullulanase synthesis was associated with the growth of the bacterium.The optimum temperature for the pullulanase activity was at 50 ℃ and the pullulanase maintained more than 50% of its maximum activity after incubation for 2 h at 70 ℃.The optimum pH value for the pullulanase activity was at 8.0; and the pullulanase retained stability in the pH range of 6.0 ~ 9.0 after incubation for 4 h.The results showed that the pullulanase from the strain exhibited high pH value and temperature stability.