Combined Optimization of Codon Usage and Glycine Supplementation Enhances the Extracellular Production of a β-Cyclodextrin Glycosyltransferase from Bacillus sp. NR5 UPM in Escherichia coli.

Nik Ida Mardiana Nik-Pa,Ezyana Kamal Bahrin,Noorjahan Banu Mohammed Alitheen,Norhayati Ramli,Suraini Abd-Aziz,Mohamad Farhan Mohamad Sobri,Mohamad Faizal Ibrahim

doi:10.3390/ijms21113919

Abstract

Two optimization strategies, codon usage modification and glycine supplementation, were adopted to improve the extracellular production of Bacillus sp. NR5 UPM β-cyclodextrin glycosyltransferase (CGT-BS) in recombinant Escherichia coli. Several rare codons were eliminated and replaced with the ones favored by E. coli cells, resulting in an increased codon adaptation index (CAI) from 0.67 to 0.78. The cultivation of the codon modified recombinant E. coli following optimization of glycine supplementation enhanced the secretion of β-CGTase activity up to 2.2-fold at 12 h of cultivation as compared to the control. β-CGTase secreted into the culture medium by the transformant reached 65.524 U/mL at post-induction temperature of 37 °C with addition of 1.2 mM glycine and induced at 2 h of cultivation. A 20.1-fold purity of the recombinant β-CGTase was obtained when purified through a combination of diafiltration and nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography. This combined strategy doubled the extracellular β-CGTase production when compared to the single approach, hence offering the potential of enhancing the expression of extracellular enzymes, particularly β-CGTase by the recombinant E. coli.

Highlights

Cyclodextrin glycosyltransferase (CGTase, extinction coefficient (EC) 2.4.1.19) is a carbohydrate-active enzyme (CAZy) that belongs to glycosyl hydrolase family 13
Bacterial Strain and Plasmid cgt-BS gene from a previous study [36] was mutated with codon usage optimization
The adaptation of rare codons of the cgt-BS gene to the preferred ones in E. coli is important to ensure an efficient expression of functional protein, as demonstrated by a codon adaptation index (CAI) of 0.78

Summary

Introduction

Cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) is a carbohydrate-active enzyme (CAZy) that belongs to glycosyl hydrolase family 13 (http://www.cazy.org/). This enzyme catalyzes transglycosylation reactions, including hydrolysis, cyclization, coupling and disproportionation [1]. Due to the problems concerning low CGTase production at longer cultivation time by the natural host cells [7], the use of a genetically engineered strain is seen as the potential approach to fulfil the higher demand of cyclodextrin at an industrial scale. In order to circumvent these obstacles, several strategies have been adopted that include codon usage optimization where codons are modified in a selected sequence to the high-frequency codons favored in the expression host [2]. Codon optimization is a synonymous mutation that modifies the nucleotide sequence of a gene without altering the amino acid sequence

Methods

Results

Conclusion