Production of extracellular exoinulinase from Kluyveromyces marxianus YS-1 using root tubers of Asparagus officinalis

Root tubers of Asparagus officinalis were used as a source of raw inulin for the production of exoinulinase (EC 3.2.1.7) from Kluyveromyces marxianus YS-1. Root extract prepared at 10 kg/cm2 pressure for 10 min showed maximum inulinase production. Medium components and process parameters were standardized to improve the enzyme production. Inulinase yield of 40.2 IU/mL in a medium containing raw inulin (3.5%), beef extract (2%), SDS (0.001%), Mn2+ (2.0 mM), Mg2+ (1.5 mM), Co2+ (2 mM) and pH 6.5 has been obtained under agitation (150 rpm) after 60 h of incubation at 30 °C at shake flask level. After optimization, the enzyme production was 4.8 times more than the basal medium. To test the feasibility of raw inulin from A. officinalis for the production of inulinase, trials were also made in a bioreactor (1.5 L). Inulinase activity of 50.2 IU/mL was obtained from raw inulin (4.0%) under agitation (200 rpm) and aeration (0.75 vvm) at 30 °C after 60 h of fermentation. Inulinase yield in bioreactor was almost six times higher than the basal medium used initially in shake flask.