Effect of chemical and physical parameters on the production of L-asparaginase from a newly isolated Serratia marcescens SK-07

Abstract

Aims: The objective of this study is to optimize the levels of carbon and nitrogen sources of the medium in shake flask experiments and evaluate the effect of pH and dissolved oxygen (DO) on the production of L-asparaginase from a newly isolated Serratia marcescens SK-07 in a batch bioreactor.

Methods and results: Central composite rotatable design (CCRD) was applied to optimize the levels of carbon and nitrogen sources of the medium in shake flask experiments. The optimal levels of L-asparagine, glucose, yeast extract and peptone were found to be 4·93, 3·81, 3·65 and 1·47 g l⁻¹, respectively, and maximal L-asparaginase production of 25·02 U mg⁻¹ was obtained under these conditions. Among the carbon sources tested, L-asparagine was identified to be the most favourable carbon source for enhanced production of L-asparaginase. The maximum L-asparaginase production of 29·89 U mg⁻¹ was achieved in a batch bioreactor at initial pH of 6·5 (uncontrolled) and DO level of 40% in the culture.

Conclusions: We have isolated, screened and identified the potential micro-organism, S. marcescens, for the production of L-asparaginase. An overall 5·55-fold increase in the production was achieved under optimal levels of carbon and nitrogen sources, DO level and at initial pH of 6·5 (uncontrolled).

Significance and impact of the study: The experiments illustrate the importance of statistical method for optimization of carbon and nitrogen sources and study the effect of physical process parameters on the production of L-asparaginase in shake flask and bioreactor, respectively. This study would be helpful for bioprocess development of bacterial L-asparaginase production.