Statistical optimization of culture conditions of mesophillic gamma-glutamyl transpeptidase from Bacillus altitudinis IH

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ORIGINAL ARTICLE

Statistical optimization of culture conditions of mesophillic gamma‑glutamyl transpeptidase from Bacillus altitudinis IHB B1644 Eshita Sharma1,2 · Arvind Gulati3 · Ashu Gulati1  Received: 2 December 2019 / Accepted: 6 May 2020 © King Abdulaziz City for Science and Technology 2020

Abstract Microbial gamma-glutamyl transpeptidase (GGT) is a key enzyme in production of several γ-glutamyl compounds with food and pharmaceutical applications. Bacterial GGTs are not commercially available in the market owing to their low production from various sources. Thus, the study was focused on achieving the higher GGT production from B. altitudinis IHB B1644 by optimizing the culture conditions using one-variable-at-a-time (OVAT) strategy. A mesophillic temperature of 28 °C, agitation 200 rpm and neutral pH 7 were found to be optimal for higher GGT titre. Among the medium components, the monosaccharide glucose served as the best carbon source over disaccharides, and yeast extract was the preferred organic nitrogen source over inorganic nitrogen sources. The statistical approaches (Plakett–Burman and response surface methodology) were further employed for the optimization of medium components. Medium composition: 0.1% w/v glucose, 0.3% w/v yeast extract, 0.03% w/v magnesium sulphate, 0.20% w/v potassium dihydrogen phosphate and 2.5% w/v sodium chloride with inoculum size (1% v/v) was suitable for higher GGT titres (449 U ml−1). Time kinetics showed the stability of enzyme up to 96 h of incubation suggesting its application in the industrial use. The proposed strategy resulted in 2.6-fold increase in the GGT production compared to that obtained in the unoptimized medium. The results demonstrated that RSM was fitting to identify the optimum production conditions and this finding should be of great importance for commercial GGT production. Keywords  Bacillus altitudinis · Gamma glutamyl transpeptidase · OVAT · Response surface methodology · l-theanine production Abbreviations °C Degree celsius h Hour % w/v Percent weight by volume mM Millimole µM Micromole Na2HPO4 Di-sodium hydrogen phosphate KH2PO4 Potassium dihydrogen phosphate NH4Cl Ammonium chloride * Ashu Gulati [email protected] 1



Food and Nutraceuticals Division, CSIR-Institute of Himalayan Bioresource Technology, Council of Scientific and Industrial Research (CSIR), PO Box 6, Palampur, Himachal Pradesh 176061, India

2



Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, Punjab, India

3

Department of Biotechnology, CSIR-Institute of Himalayan Bioresource Technology, PO Box 6, Palampur, Himachal Pradesh 176061, India



NaCl Sodium chloride MgCl2 Magnesium chloride CaCl2 Calcium chloride MgSO4∙7H2O Magnesium sulphate heptahydrate K2HPO4∙3H2O Di-potassium hydrogen phosphate trihydrate rpm Revolution per minute ml Millilitre % v/v Percent volume by volume L Litre

Introduction Catalytic properties of microbial-derived enzymes have been widely applied in biotechnological procedures due to their hig