Dosoretz C G, Rothschild N, Hadar Y
Department of Environmental Engineering and Water Resources, Technion-Israel Institute of Technology, Haifa.
Appl Environ Microbiol. 1993 Jun;59(6):1919-26. doi: 10.1128/aem.59.6.1919-1926.1993.
The ligninolytic enzymes synthesized by Phanerochaete chrysosporium BKM-F-1767 immobilized on polyurethane foam were characterized under limiting, sufficient, and excess nutrient conditions. The fungus was grown in a nonimmersed liquid culture system under conditions close to those occurring in nature, with nitrogen concentrations ranging from 2.4 to 60 mM. This nonimmersed liquid culture system consisted of fungal mycelium immobilized on porous pieces of polyurethane foam saturated with liquid medium and highly exposed to gaseous oxygen. Lignin peroxidase (LIP) activity decreased to almost undetectable levels as the initial NH4+ levels were increased over the range from 2.4 to 14 mM and then increased with additional increases in initial NH4+ concentration. At 45 mM NH4+, LIP was overproduced, reaching levels of 800 U/liter. In addition, almost simultaneous secretion of LIP and secretion of manganese-dependent lignin peroxidase were observed on the third day of incubation. Manganese-dependent lignin peroxidase activity was maximal under nitrogen limitation conditions (2.4 mM NH4+) and then decreased to 40 to 50% of the maximal level in the presence of sufficient or excess initial NH4+ concentrations. Overproduction of LIP in the presence of a sufficient nitrogen level (24 mM NH4+) and excess nitrogen levels (45 to 60 mM NH4+) seemed to occur as a response to carbon starvation after rapid glucose depletion. The NH4+ in the extracellular fluid reappeared as soon as glucose was depleted, and an almost complete loss of CO2 was observed, suggesting that an alternative energy source was generated by self-proteolysis of cell proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
对固定在聚氨酯泡沫上的黄孢原毛平革菌BKM-F-1767合成的木质素分解酶，在营养限制、充足和过量条件下进行了表征。该真菌在非浸没液体培养系统中生长，条件接近自然环境，氮浓度范围为2.4至60 mM。这种非浸没液体培养系统由固定在多孔聚氨酯泡沫块上的真菌菌丝体组成，泡沫块浸有液体培养基并高度暴露于气态氧。随着初始NH4+水平从2.4 mM增加到14 mM，木质素过氧化物酶（LIP）活性降至几乎检测不到的水平，然后随着初始NH4+浓度的进一步增加而增加。在45 mM NH4+时，LIP过量产生，达到800 U/升的水平。此外，在培养的第三天观察到LIP几乎同时分泌以及锰依赖性木质素过氧化物酶的分泌。锰依赖性木质素过氧化物酶活性在氮限制条件下（2.4 mM NH4+）最高，然后在初始NH4+浓度充足或过量时降至最高水平的40%至50%。在充足氮水平（24 mM NH4+）和过量氮水平（45至60 mM NH4+）存在下LIP的过量产生似乎是对葡萄糖快速耗尽后碳饥饿的一种反应。一旦葡萄糖耗尽，细胞外液中的NH4+就会重新出现，并且观察到几乎完全没有CO2，这表明细胞蛋白质的自我蛋白水解产生了替代能源。（摘要截短于250字）
