Biotechnology and Bioprocess Engineering 2019; 24(5): 824-832  
Production of Recombinant Human Asparaginase from Escherichia coli under Optimized Fermentation Conditions: Effect of Physicochemical Properties on Enzyme Activity
Rajesh Kumar Kante1, Silpa Somavarapu2, Sandeep Vemula1, Chandrika Kethineni3, Maheshwara Reddy Mallu1, and Srinivasa Reddy Ronda1,*
1Department of Biotechnology, Centre for Bioprocess Technology, K L University, Guntur 522 502, Andhra Pradesh, India
2Department of Food Technology, Vikrama Simhapuri University, Kakutur, Nellore 524 320, Andhra Pradesh, India
3Department of Petroleum Engineering, K L University, Guntur 522 502, Andhra Pradesh, India
Correspondence to: Srinivasa Reddy Ronda
Department of Biotechnology, Centre for Bioprocess Technology, K L University, Guntur 522 502, Andhra Pradesh, India
Tel: +91-8645-246948; Fax: +91-8645-247249
E-mail: rsr@kluniversity.in
Received: April 19, 2019; Accepted: May 7, 2019; Published online: October 31, 2019.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The recombinant human asparaginase (rhASP) plays an important role in the treatment of acute lymphoblastic leukemia. In the present work, volumetric mass transfer coefficient (kLa) values are derived from the E. coli cultivation under different agitation and aeration conditions, in order to improve the rhASP productivity. The aeration and agitation conditions were systematically optimized by the kLa. The maximum biomass (2.4 g/L) and rhASP (1.68 g/L) are achieved with the kLa of 0.024 s-1 at 1.5 lpm and 700 rpm process conditions. The kinetic properties of purified rhASP are also extensively studied and optimized for the maximal enzyme activity. The optimal pH, temperature and incubation duration conditions for accomplishing maximum enzyme activity are found to be 9.0, 40°C, and 30 min, respectively. The optimum substrate concentration and substrate specificity for the highest enzyme activity are of 0.07 M and L-asparagine, respectively. The enzyme activity (204 IU/mL) is significantly improved in the presence of sodium metal (Na+) ions and the inhibitors 2- mercaptoethanol, bromoacetic acid and urea have presented the highest inhibition rate on rhASP activity. The enzyme kinetic parameters Km and Vmax of the purified rhASP are recorded as 2.25 mM and 250 IU/mL, respectively. This work provides the extensive characteristic properties of rhASP enzyme, which enables us to place in a competition for the development of oncology drugs.
Keywords: asparaginase, volumetric mass transfer coefficient, purification, enzyme activity, kinetic properties


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