Recombinant expression of β-fructofuranosidase from Arthrobacter sp. EpRS66 and enzymatic synthesis of lactosucrose

Abstract:

[Background] Lactosucrose, a novel functional oligosaccharide, has been demonstrated capable of improving the gut microbiota and boosting the immunity of humans and animals. Since it is increasingly utilized in food and feed industries, the market demand for lactosucrose has been increasing year by year. The industrial production of lactosucrose mainly uses β-fructofuranosidases due to the high product specificity. However, the conversion rates of existing enzymes were generally low, which made the production cost remaining high. [Objective] To identify new β-fructofuranosidases for the enzymatic properties and industrial production of lactosucrose. [Methods] We identified a β-fructofuranosidase gene from Arthrobacter sp. EpRS66 and expressed it in Escherichia coli. Furthermore, we characterized the enzymatic properties of the recombinant β-fructofuranosidase and optimized the optimum reaction conditions for the production of lactosucrose. [Results] The recombinant enzyme showed the optimal performance at 40 ℃ and pH 6.0. It maintained good stability within the range of pH 5.0-8.0 and had a half-life of 20 min at 40 ℃. Under the reaction conditions of 40 ℃ and pH 6.0, the conversion rate of lactosucrose reached 32.2% at the time point of 3 h with substrates of 15% sucrose and 15% lactose and an enzyme addition of 25 μg/mL. Moreover, with high concentrations of substrates (30% sucrose and 30% lactose), the conversion rate reached 30.8%. [Conclusion] This study provides a novel β-fructofuranosidase that can effectively catalyze the formation of lactosucrose, offering a new choice for industrial production of lactosucrose.