Microbial production of inulo-oligosaccharides by an endoinulinase from Pseudomonas sp expressed in Escherichia coli

In an attempt to utilize the whole cell as a biocatalyst for inulo-oligosac charide (IOS) production from inulin, the endoinulinase gene (inu1) of Pseu domonas sp. was cloned into the plasmid pBR322 using EcoRI restriction endo nuclease and Escherichia coli HB101 as the host strain. The endoinulinase f rom E. coli IIB101/pKMG50 was constitutively expressed, producing a high yi eld of IOS (78%). In a batchwise reaction, the initial enzyme concentration determined the total oligosaccharide yield, and excess enzyme decreased th e total oligosaccharide yield due to the formation of high amounts of free sugars such as glucose and fructose. The recombinant E. coli expressing end oinulinase activity were immobilized on a polystyrene carrier material, res ulting in a dramatically enhanced thermal stability of the enzyme. Continuo us production of IOS from inulin was also carried out at 50 degrees C using a bioreactor packed with the immobilized cells. Under the optimal operatio n conditions, continuous production of IOS was achieved with a productivity of 150 g/l.h for 17 d at 50 degrees C without significant loss of initial activity.