The effects of RecO deficiency in Lactococcus lactis NZ9000 on resistance to multiple environmental stresses

BACKGROUNDMultiple stresses could cause damage to DNA and other macromolecules. RecO, belonging to the family of DNA repair proteins, plays an important part in homologous recombination and replication repair. In order to explore the role of RecO in overcoming multiple stresses, a mutant of recO deletion is constructed in Lactococcus lactis ssp. cremorisNZ9000. RESULTSCompared with the mutant strain, the original strain L. lactisNZ9000 shows better performance in growth under multiple stresses. The survival rates of the original strain under acid, osmotic and chill stresses are 13.49-, 2.78- and 60.89-fold higher. In our deeper research on fermentation capability under osmotic stress, lactate dehydrogenase activity after 8 h fermentation, maximum lactate acid production, lactate yield and maximum lactate productivity of L. lactisNZ9000 are 1.63-, 1.28-, 1.28- and 1.5-fold higher, respectively. CONCLUSIONResults indicate that RecO has positively improved the survival of L. lactisNZ9000, protected its key enzymes and enhanced its fermentation efficiencies. Our research confirms the role of RecO in enhancing tolerances to multiple stresses of L. lactisNZ9000, and puts forward the suggestion that RecO could be used in other industrial microorganisms as a new anti-stress component to improve their resistance to various stresses. (c) 2014 Society of Chemical Industry