The use of protease-deficient
E. coli strains, which carry mutations that eliminate
the production of proteases may also improve the yield
of recombinant protein by reducing proteolytic degradation.
E. coli strain BL-21, is deficient in two proteases
encoded by the lon (cytoplasmic) and ompT
(periplasmic) genes. Rather than the external parameters,
targeted methods such as modifications in protease or secretion
pathways can provide the insight into biology of
recombinant proteins [53]. In E. coli, complex and large
therapeutic proteins can be secreted in periplasm as it
provides an oxidizing environment and help in forming
disulphide bonds, which facilitate the proper folding
of recombinant proteins and likely to yield reliable
N- terminus of expressed protein [54]. Periplasm has advantages
over cytoplasm in less protein concentration
and proteolytic activity, improve the production titer
[55], and enhance the solubility of recombinant protein.
Altogether, with these advanced modifications and developments
ease the process of target protein production
thus accelerating the drug development [56].