一株海洋过氧化氢酶高产菌的鉴定及产酶条件优化

Identification of a Marine Bacterium Producing High-Level Catalase and Optimization of Its Fermentation Conditions

对来自青岛近海海域底泥的一株产过氧化氢酶菌株YS0810进行形态学观察、16S rDNA序列同源性分析及生理生化特性的鉴定,在250 ml摇瓶中进行发酵产酶条件优化。初步确定该菌属于不动杆菌属Acinetobacter。发酵培养的最佳碳、氮源分别为蔗糖20 g/L和蛋白胨15 g/L,无机盐MgSO4·7H2O、NaCl、KH2PO4最佳浓度分别为0.9、5.0和1.0 g/L;菌株在培养基起始pH=7.0、4%接种量、50 ml装液量和25℃的条件下发酵24 h获得较高的酶产量。在最佳培养条件下酶产量为2469 U/ml,是优化前的5倍。

Catalases are a type of enzymes that can effectively decompose hydrogen peroxide into water and oxygen. Because of their ubiquitous distribution in all aerobic microorganisms, plants and animals, they are widely used in food, pharmaceutical, chemical industries and environmental protection. In this study we examined the bacterial strain YS0810 collected from the sediment in Yellow Sea that produces catalase at a high level. We determined the growth conditions of this strain which is optimal for the catalase production. Phylogenetic analysis of the 16 S rDNA of this strain was applied to determine its taxonomic rank. The conventional morphological, physiological and biochemical methods of taxonomy were also applied to differentiate the YS0810 from its phylogenetic relatives. We used 250 ml shake flasks to carry out the single factor experiments to identify the important growth factors for the strain YS0810. The phylogenetic tree indicated that strain YS0810 belonged to the genus Acinetobacter, with the highest sequence similarity to Acinetobacter haemolyticus DSM 6962^T（98.7%）. However, YS0810 was not a strain of A. haemolyticus. This was consistent with the results of the comparison between YS0810 and other Acinetobacter species in terms of their morphological, physiological and biochemical characteristics. Peptone and sucrose were determined as the optimal nitrogen and carbon sources from several candidates. Our experimental results indicated that the maximum yield of the catalase was generated by YS0810 under the conditions shown below： peptone 15 g/L, sucrose 20 g/L, MgSO4·7H2O 0.9 g/L, NaCl 5.0 g/L, KH2PO4 1.0 g/L, broth content at 50 ml, the inoculum at 4%, initial pH 7.0, the temperature at 25°C and the culture time of 24 h. The verification experiment carried out in the optimal conditions above showed that the highest catalase activity was 2469 U/ml, which is five-time higher than before the optimization. In conclusion, the yield of catalase was markedly raised in the optimized fermentation conditions.