Improving acid and oxidative stress resistance using a prokaryotic gene identified by functional metagenomics.

Innovations in obtaining products from lignocellulosic biomass have been largely based on the improvement of microorganisms and enzymes capable of degrading these materials. To complete the whole process, microorganisms must be able to ferment the resulting sugars and tolerate high concentrations of product, osmotic pressure, ion toxicity, temperature, toxic compounds from lignocellulose pretreatment, low pH, and oxidative stress. In this work, we engineered laboratory and industrial strains by combining a gene () recovered from a metagenomic approach with different native and synthetic promoters to obtain improved acid and oxidative stress resistance. Laboratorial strains harboring gene under the control of the synthetic stress responsive PCCW14v5 showed increased survival rates after 2 h exposure to pH 1.5. The gene was also able to significantly enhance the tolerance of the industrial strain to high concentrations of HO when combined with PTEF1, PYGP1 or PYGP1v7 after 3 h exposure.