Introducing a thermotolerant Gluconobacter japonicus strain, potentially useful for coenzyme Q₁₀ production

In this report, Gluconobacter strains were screened for coenzyme Q₁₀ (CoQ₁₀) production. A thermotolerant strain, Gluconobacter japonicus FM10, was eventually employed for CoQ₁₀ production optimization. To do so, a two-step optimization strategy was used. The first step focused on biomass increase and the second step focused on increase in CoQ₁₀ production. Factors including temperature, pH, carbon, and nitrogen sources were optimized at the first step, and temperature, pH, and aeration were optimized at the second step. The batch culture fermentation was used with the optimized factors of the first phase (30 °C, pH 6.5, D-sorbitol, and yeast extract-peptone as the carbon and nitrogen sources). After 18 h, the temperature, pH, and aeration were shifted to the optimized values of the second step (36 °C, pH 7, and no aeration). By this strategy, the dry cell mass (17.1 g/L) and CoQ₁₀ (23.2 mg/L) were obtained after 20 h, which the latter was 2.3 times higher than that of the first step of optimization. Among the conditions tested, carbon source was the most important factor on the cell growth at the first step while no aeration was the key factor for CoQ₁₀ production in the second step of optimization.