Fig. 1

Trends in the selection of experimental design parameters for the literature surveyed in recombinant production of difficult to express (DtE) enzymes and industrially relevant enzymes in E. coli (year coverage: 2010–2020). A Breakdown of the industries in which DtE enzymes were most commonly employed or demanded. B Breakdown of the most common enzyme classes that DtE enzymes are affiliated to. C Breakdown of the most utilized commercial E. coli expression strains and their modified versions. D Frequency of plasmids (vector) used in different experimental designs. E Breakdown of the most utilized fusion tags in recombinant vector designs