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This article investigates the production and optimization of levansucrase using synthetic medium by Zymomonas mobilis NRRL B-14023. Response surface methodology was used to investigate the effects of three different fermentation parameters on levansucrase enzyme production. Maximum levansucrase activity of 13.3 µmol glucose/min was obtained at the optimum levels of process variables (pH 4.90, initial sucrose concentration 159.01 g/L and fermentation temperature 30.3°C). Response surface methodology was found to be useful in optimizing and determining the interactions among process variables. The purity of levansucrase used in enzyme assays were analyzed by SDS-PAGE and a dominant protein band of size around 47 kDa was obtained. The sequence of the produced enzyme was determined by peptide mass fingerprinting. The presence of kestose in the reaction mixture showed that Z. mobilis levansucrase can produce fructooligosaccharides. This study fulfills the lack of mathematical and statistical approaches in optimizing the levansucrase production by Z. mobilis. Practical applications Levansucrases are responsible for the production of valuable fructans; fructooligosaccharides (FOS) and levan. Fructooligosaccharides are sugar polymers three times less sweet than sucrose and naturally present in some foods. FOS have important promising use in the food industry due to their properties such as solubility in water, stability during storage, low calorie value, and prebiotic effects. In this research, the production of microbial levansucrase was optimized for potential industrial applications by response surface methodology. Future studies will focus on conversion of intrinsic sucrose of foods to FOS using levansucrase. [ABSTRACT FROM AUTHOR]

• Zymomonas mobilis levansucrase was used to produce kestose in carob molasses. • Levansucrase treatment did not adversely affect the quality of the final product. • The 5-HMF content of the final product did not increase during storage. • Enzymatic sugar conversion can be used to prevent 5-HMF formation. Fructooligosaccharides have important potential use in the food industry due to their properties such as solubility in water, stability in acidity of fruit juices and during storage, low-calorie value and prebiotic effects. In this study, for the first time, Zymomonas mobilis levansucrase was used for in situ 6-kestose production in carob molasses. The produced kestose was stable during storage at 20 °C for 4 months. The product was evaluated for color, non-enzymatic browning index and titratable acidity during storage and the quality of the product was found comparable to that of control. Furthermore, the decreased amount of sucrose resulted in the prevention of 5-hydroxymethylfurfural (5-HMF) formation during storage. As a result, carob molasses was converted into a high-quality prebiotic product with decreased sucrose content and reduced 5-HMF quantities, and a new method was developed to prevent 5-HMF formation in fruit juices and molasses. [ABSTRACT FROM AUTHOR]