Purification and Properties of a New L-Sorbose Dehydrogenase Accelerative Protein from Bacillus megaterium Bred by Ion-Beam Implantation

摘要

Bacillus megaterium BM302 bred by ion-beam implantation produces L-sorbosedehydrogenase accelerative protein (SAP) to accelerate the activity of L-sorbose dehydrogenase(SDH) of Gluconobacter oxydans in the 2-keto-L-gulonic acid (2KLG) fermentation from L-sorboseby the mixed culture of B.megaterium BM302 and G.oxydans.The SAP purified by threechromatographic steps gave 35-fold purification with a yield of 13% and a specific activity of5.21 units/mg protein.The molecular weight of the purified SAP was about 58 kDa.The SDHaccelerative activity of SAP at pH 7 and 50℃ was the highest.Additionally,it retained 60%activity at a pH range of 6.5～10 and was stable at 20℃～60℃.After 0.32-unit SAP was addedto the single cultured G.oxydans strains,the SDH activity was apparently accelerated and the2KLG yield of GO29,GO112,G0 and G113 was enhanced 2.1,3.3,3.5 and 2.9 folds respectivelyover that of the strains without the addition of SAP.