Here we summarize the main indications pointing out the chaperone side-effects, mainly focusing on DnaK, GroEL and their cooperating folding modulators.Table 1Main undesired side effects observed during chaperone co-production on the quality and yield of recombinant proteins produced in E. coli, as exemplified by representative studies.DnaKDnaK, homolog of the eukaryotic Hsp70, is the major cytoso