Production, Characterization and Optimal Performance Studies of Glucose Isomerase by Achromobacter xylosoxidans mck-4 Isolated from Starch Milling Wastes
M. C. Mbagwu
International Breweries PLC, Gateway Plant, Sagamu, Ogun State, Nigeria.
E. J. Egong *
Department of Microbiology, University of Nigeria, Enugu State, Nigeria.
O. D. Akan
College of Food Engineering, Central South University of Forestry and Technology, Changsha, Hunan, China.
*Author to whom correspondence should be addressed.
Abstract
Seventy-five (75) bacterial isolates from starch milling wastes in Nsukka, Nigeria were screened for their ability to produce glucose isomerase (GI). The isolate Achromobacter xylosoxidans Mck-4 gave the highest activity of intracellular GI using starch casein agar (SCA) medium supplemented with nystatin to eliminate fungi contaminations, incubated at 30°C for 48 hours and pH 7. The SDS PAGE showed that the enzyme was partially purified and the band was near the protein marker of 43 KDa. The enzyme was purified 4.7 fold with a specific activity of 6.4±0.52 U/mg of protein and 30.9% enzyme recovery in the final desalted sample. The Km value calculated for glucose by Lineweaver Burk plot is 0.89 moles and Vmax was 6.4±0.52 U/mg. The highest activity of the enzyme was at a temperature of 70˚C and pH 7 and maximally activated by the cations; magnesium and cobalt with magnesium having the highest effect followed by manganese and cobalt in individual effects. These parameters for the production of GI by Achromobacter xylosoxidans mck-4 are well in the range of economic feasibility; therefore such a process has good chances for industrialization. It is recommended that the gene from our isolate should be isolated and cloned in GRAS status organism to scale up enzyme production and optimize industrial production of high fructose corn syrup (HFCS) in Nigeria using agro-residues.
Keywords: D-glucose/Xylose isomerase, Achromobacter xylosoxidans, fructose, Km (Michaelis Menten constant), agro-residues, enzyme activity