Biocalorimetric investigation of inulinase production by kluyveromyces marxianus and heat based model prediction

Abstract

Metabolic heat has been established as an immensely useful parameter for understanding a bioprocess. Biocalorimetry (BioRC1e) measures the metabolic activity of population of cells and the metabolic change can be monitored on-line and in real time. Heat dissipation signals can also qualitatively be correlated with the evolution of the culture enabling identification of pertinent metabolic events. newlineInulinase is one of the industrially important enzymes and finds applications in the food industry and serves as a catalyst for conversions of agro-industrial waste to bio-products. The motive of the present study is to formulate a biokinetic-model to explain and predict inulinase production by Kluyveromyces marxianus with sucrose as a substrate. An interrelation between inulinase production kinetics and metabolic heat allows to monitor online, the rate of enzyme production, using just the biocalorimetric (Bio RC1e) heat values. The study revealed that inulinase production was significantly influenced by the listed bioprocess parameters such as pH (5), inoculum size (2 %), sucrose (10 g/L) and ammonium sulphate (7.5 g/L). Heat based newlinemonitoring of inulinase production with parameters such as aeration rate and agitation rate showed inulinase was strongly influenced by shear stress and led to poor dissolved oxygen levels. Optimum aeration and agitation rates for inulinase production were found to be 1 LPM and 150 RPM respectively. Maximum enzyme activity of 20.98 IU/mL was achieved under this condition. Batch and fed-batch synthesis of inulinase by K. marxianus were monitored in a bio reaction calorimeter for the first time. The strategic feeding of the substrate (3 ghr-1 at a dilution rate of 0.002 hr-1) in fed-batch helped not only to improve the inulinase activity by extending its stationary growth phase but also maintain a growth rate of 0.2 g.hr-1 and specific growth rate above 0.002 hr-1 after 28th hr.better in terms of area, and power consumption than the conventional approaches. newline newline