Characterization of a Neutrophil Pullulanaseand Its Application in Sweet Potato Vermicelli Processing

Abstract:

This research aimed to develop a neutral pullulanase with stable activity in a wide pH range, which can adapt to the manufacturing process of vermicelli with sweet potato powder as raw material. The pullulanse-encoding gene pul3665 was cloned from genome DNA of Geobacillus subterraneus XQ3665 by PCR and heterologously expressed. Specific activity of the purified recombinant enzyme PUL3665 is 32 U/mg. The optimal temperature and pH of PUL3665 were 55 ℃ and 6.5, respectively. The PUL3665 maintain 80% of its highest activity in the range of pH 5.5~7.7. The product of enzymatic degradation of pullulan was maltotriose, and the PUL3665 did not degrade amylose. Thus, the PUL3665 belongs to type I pullulanases. The crude enzyme of PUL3665 expressed by B. subtilis was used in the traditional vermicelli-making process. The paste was treated with PUL3665 at a dose of 2 U/g of paste. Vermicellis were successfully achieved using different kinds of sweet potato powder as raw materials. Neitheralum nor other additives were used. The quality of the finished vermicelli made from PUL3665 treated paste was about the same to that of the vermicelli which was made with alum as aditives. The PUL3665 is expectedto be developed into a highly effective and reliable substitute of alum in vermicelli production.