Contribution of the activated catalase to oxidative stress resistance and γ-aminobutyric acid production in Lactobacillus brevis

• We employed a genetic approach to clone, express and characterize the katE of L. brevis CGMCC1306.
• The katE gene product was activated by heme and is essential for optimal resistance to H2O2.
• The enhanced homologous CAT expression in L. brevis was achieved using the NICE system.
• Overexpression of the KatE led to a marked increased survival in oxidizing environment.
• A novel feasible approach to enhance the GABA production level was established by improving the antioxidative properties.

Lactic acid bacteria (LAB) are generally sensitive to H2O2, a compound which can paradoxically produce themselves and lead to the growth arrest and cell death. To counteract the potentially toxic effects of this compound, the gene katE encoding a heme-dependent catalase (CAT) belonging to the family of monofunctional CATs was cloned from Lactobacillus brevis CGMCC1306. The enhanced homologous CAT expression was achieved using the NICE system. L. brevis cells with overexpressed CAT showed 685-fold and 823-fold higher survival when exposed to 30 mmol/L of H2O2 and long-term aerated stress (after 72 h), respectively, than that of the wild type cells. Furtherly, the effects of activated CAT on GABA production in L. brevis were investigated. A GABA production level of 66.4 g/L was achieved using two-step biotransformation that successively employed the growing and resting cells derived from engineering L. brevis CAT. These results demonstrated clearly that overexpression of the KatE gene in L. brevis led to a marked increased survival in oxidizing environment, and shed light on a novel feasible approach to enhance the GABA production level by improving the antioxidative properties.