The state of the art in the production of fructose from inulin enzymatic hydrolysis

The present work reviews the main advancements achieved in thelast decades in the study of the fructose production process by inulin enzymatichydrolysis.With the aim of collecting and clarifying the majority of the knowledgein this area, the research on this subject has been divided in three mainparts: a) the characteristics of inulin (the process reactant); b) the properties ofthe enzyme inulinase and its hydrolytic action; c) the advances in the study ofthe applications of inulinases in bioreactors for fructose production.Many vegetable sources of inulin are reported, including information abouttheir yields in terms of inulin. The properties of inulin that appear relevant forthe process are also summarized, with reference to their vegetable origin.The characteristics of the inulinase enzyme that catalyzes inulin hydrolysis,together with the most relevant information for a correct process design andimplementation, are described in the paper. An extended collection of dataon microorganisms capable of producing inulinase is reported. The followingcharacteristics and properties of inulinase are highlighted: molecular weight,mode of action, activity and stability with respect to changes in temperatureand pH, kinetic behavior and effect of inhibitors. The paper describes in detailthe main aspects of the enzyme hydrolysis reaction; in particular, how enzymeand reactant properties can affect process performance. The properties ofinulinase immobilized on various supports are shown and compared to thoseof the enzyme in its native state.Finally, a number of applications of free and immobilized inulinasesand whole cells in bioreactors are reported, showing the different operatingprocedures and reactor types adopted for fructose production from inulin ona laboratory scale.