Glycerol Utilization In Gluconobacter Oxydans 621H And Hydrolysis Of Inulin Catalyzed By Fe³⁺

Gluconobacter oxydans is an important biological catalyst,which can incompletely oxidize a variety of sugars or alcohols to produce corresponding compounds-G.oxydans is always cultured in sorbitol or mannitol organic medium,the price of which is very expensive.Therefore,it's very significant for industrial application to find an inexpensive medium of the strain.In this study,the growth of G.oxydans on minimal mediums with different common carbon source was examined.It was found that glycerol could support the growth of G.oxydans in minimal mediums,and we got a derivative,?1068?0854.The cell yield of ?1068?0854 from glycerol minimal medium was 0.20 g DCW/g,which was 6.7 times compared with wild type,and ?1068?0854 had higher glucose dehydrogenase activity.?1068?0854 from glycerol minimal medium reduces production cost and has catalytic advantage,giving more values to the industry application.Xylose catalyzed by ?1068?0854 resting cells from glycerol minimal medium produced 61.5 g/L xylonate,and the yield was 1.05 g/g.According to the genome annotation,G.oxydans contains a glycerol operon,which is composed of glpD(glycerol-3-phosphate dehydrogenase encoded by gox2088),glpF(glycerin facilitator encoded by gox2089),glpK(glycerol kinase encoded by gox2090)and glpR(transcriptional regulatory protein encoded by gox2087).The second part of this paper,the regulatory mechanism of this operon was explored.RT-PCR analysis indicated that the operon is composed of glpR,glpD,glpF and glpK.GlpR is the repressor protein of this operon,and its binding region is the intergenic region of and Although glycerol-3-phosphate is a common inducer of glycerol operon,glycerol and its intermediates can not induce the glycerol operon in G.oxydans.Inulin is a kind of linear polysaccharide.It is composed of fructoses connected by ?(2,1)glycosidic bonds and a glucose connected to the end by an a(2,1)glycosidic bond.Hydrolysis of inulin is the first problem to be solved.Inulin is usually hydrolysed by enzyme or acid.In the third part of this paper,we found that Fe3+ can hydrolyse inulin under high temperature.In this way the final concentration of sugar solution is 854.16 g/L,and the concentration of Fe3+is about 1.35 mM.The hydrolysate can be used for microbial fermentation and has high economic value.