Exploring codon context bias for synthetic gene design of a thermostable invertase in Escherichia coli

•Application of codon context fitness for heterologous enzyme expression in E. coli.•Novel design criteria of secondary structure for codon optimization in E. coli.•Increased invertase activity of 40% by codon context optimization over wild type.•Importance of codon context fitness for heterologous protein expression in E. coli.