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Background  Second-generation ethanol production is a clean bioenergy source with potential to mitigate fossil fuel emissions. The engineering of  Saccharomyces cerevisiae  for xylose utilization is an essential step towards the production of this biofuel. Though xylose isomerase (XI) is the key enzyme for xylose conversion, almost half of the XI genes are not functional when expressed in  S. cerevisiae . To date, protein misfolding is the most plausible hypothesis to explain this phenomenon.    Results  This study demonstrated that XI from the bacterium  Propionibacterium acidipropionici  becomes functional in  S. cerevisiae  when co-expressed with GroEL-GroES chaperonin complex from  Escherichia coli . The developed strain BTY34, harboring the chaperonin complex, is able to efficiently convert xylose to ethanol with a yield of 0.44 g ethanol/g xylose. Furthermore, the BTY34 strain presents a xylose consumption rate similar to those observed for strains carrying the widely used XI from the fungus  Orpinomyces sp . In addition, the tetrameric XI structure from  P. acidipropionici  showed an elevated number of hydrophobic amino acid residues on the surface of protein when compared to XI commonly expressed in  S. cerevisiae .    Conclusions  Based on our results, we elaborate an extensive discussion concerning the uncertainties that surround heterologous expression of xylose isomerases in  S. cerevisiae . Probably, a correct folding promoted by GroEL-GroES could solve some issues regarding a limited or absent XI activity in  S. cerevisiae . The strains developed in this work have promising industrial characteristics, and the designed strategy could be an interesting approach to overcome the non-functionality of bacterial protein expression in yeasts.    Electronic supplementary material  The online version of this article (10.1186/s12896-017-0389-7) contains supplementary material, which is available to authorized users.

Conversion of an inactive xylose isomerase into a functional enzyme by co-expression of GroEL-GroES chaperonins in Saccharomyces cerevisiae