Manipulation of culture conditions for extensive extracellular catalase production by Exiguobacterium oxidotolerans T-2-2T

A hydrogen peroxide (H2O2)-resistant bacterium, Exiguobacterium oxidotolerans T-2-2T, secretes extracellular catalase. A low shaking frequency (60 rpm) was employed following the observation that a higher amount of extracellular catalase was produced under this condition compared with the previous shaking frequency (120 rpm). The cell concentration reached approximately 4.5 × 106 cells mL−1, at which the initiation of extracellular catalase production was triggered, while the production of the extracellular catalase was largely dependent on that of the intracellular catalase. The best initial aeration condition for extracellular catalase production was 7.5 mg O L−1, which is 95 % of that of the air-saturated state measured under the low shaking frequency. In addition, although the total productivity of catalase was unchanged, introduction of aminolevulinic acid and Tween 60 promoted extracellular production. The extracellular and intracellular catalase productivities were 16,000 and 6,000 U mL−1 of spent culture medium, respectively.