Nanou K, Roukas T, Kotzekidou P
Department of Food Science and Technology, Aristotle University of Thessaloniki, Box 250, 54124 Thessaloniki, Greece.
Appl Microbiol Biotechnol. 2007 Feb;74(2):447-53. doi: 10.1007/s00253-006-0666-1. Epub 2006 Nov 14.
The role of hydrolytic enzymes (proteases and chitinase) and oxidative stress in the autolysis and morphology of Blakeslea trispora during beta-carotene production from a chemically defined medium in shake flask culture was investigated. The process of cellular autolysis was studied by measuring the changes in biomass dry weight, pH, concentration of beta-carotene, specific activity of the hydrolytic enzymes and micromorphology of the fungus using a computerized image analysis system. In addition, the phenomenon of autolysis was associated with high concentrations of reactive oxygen species (ROS). The accumulation of ROS produced during fermentation causes oxidative stress in B. trispora. Oxidative stress was examined in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). The profile of the specific activities of the above enzymes appeared to correlate with the oxidative stress of the fungus. The high activities of CAT and SOD showed that B. trispora is found under oxidative stress during beta-carotene production. The culture began to show signs of autolysis nearly in the growth phase and autolysis increased significantly during the production phase. The morphological differentiation of the fungus was a result of the degradation of the cell membrane by hydrolytic enzymes and oxidative stress. Increased beta-carotene production is correlated with intense autolysis of clumps, which has as a consequence the increase of the freely dispersed mycelia.
研究了水解酶（蛋白酶和几丁质酶）以及氧化应激在摇瓶培养中从化学成分确定的培养基生产β-胡萝卜素过程中，对三孢布拉氏霉菌自溶和形态的作用。通过使用计算机图像分析系统测量生物量干重、pH值、β-胡萝卜素浓度、水解酶的比活性以及真菌的微观形态变化，研究了细胞自溶过程。此外，自溶现象与高浓度的活性氧（ROS）有关。发酵过程中产生的ROS积累会导致三孢布拉氏霉菌产生氧化应激。从两种关键防御酶：过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性方面检测了氧化应激。上述酶的比活性谱似乎与真菌的氧化应激相关。CAT和SOD的高活性表明三孢布拉氏霉菌在β-胡萝卜素生产过程中处于氧化应激状态。培养物几乎在生长阶段就开始出现自溶迹象，并且在生产阶段自溶显著增加。真菌的形态分化是水解酶和氧化应激导致细胞膜降解的结果。β-胡萝卜素产量的增加与团块的强烈自溶相关，这导致自由分散的菌丝体增加。
