Müller Christian, McIntyre Mhairi, Hansen Kim, Nielsen Jens
Center for Process Biotechnology, BioCentrum-DTU, Technical University of Denmark, 2800 Kgs. Lyngby.
Appl Environ Microbiol. 2002 Apr;68(4):1827-36. doi: 10.1128/AEM.68.4.1827-1836.2002.
Morphology and alpha-amylase production during submerged cultivation were examined in a wild-type strain (A1560) and in strains of Aspergillus oryzae in which chitin synthase B (chsB) and chitin synthesis myosin A (csmA) have been disrupted (ChsB/G and CM101). In a flowthrough cell, the growth of submerged hyphal elements was studied online, making it possible to examine the growth kinetics of the three strains. The average tip extension rates of the CM101 and ChsB/G strains were 25 and 88% lower, respectively, than that of the wild type. The branching intensity in the CM101 strain was 25% lower than that in the wild type, whereas that in the ChsB/G strain was 188% higher. During batch cultivation, inseparable clumps were formed in the wild-type strain, while no or fewer large inseparable clumps existed in the cultivations of the ChsB/G and CM101 strains. The alpha-amylase productivity was not significantly different in the three strains. A strain in which the transcription of chsB could be controlled by the nitrogen source-regulated promoter niiA (NiiA1) was examined during chemostat cultivation, and it was found that the branching intensity could be regulated by regulating the promoter, signifying an important role for chsB in branching. However, the pattern of branching responded very slowly to the change in transcription, and increased branching did not affect alpha-amylase productivity. alpha-Amylase residing in the cell wall was stained by immunofluorescence, and the relationship between tip number and enzyme secretion is discussed.
在野生型菌株（A1560）以及几丁质合酶B（chsB）和几丁质合成肌球蛋白A（csmA）已被破坏的米曲霉菌株（ChsB/G和CM101）中，研究了深层培养过程中的形态学和α-淀粉酶产生情况。在流通池中，对深层菌丝体元素的生长进行了在线研究，从而能够检测这三种菌株的生长动力学。CM101和ChsB/G菌株的平均顶端延伸率分别比野生型低25%和88%。CM101菌株的分支强度比野生型低25%，而ChsB/G菌株的分支强度比野生型高188%。在分批培养过程中，野生型菌株形成了不可分离的菌团，而在ChsB/G和CM101菌株的培养中不存在或存在较少的大的不可分离菌团。三种菌株的α-淀粉酶生产率没有显著差异。在恒化器培养过程中，检测了一种其中chsB转录可由氮源调节启动子niiA（NiiA1）控制的菌株，发现通过调节启动子可以调节分支强度，这表明chsB在分支中起重要作用。然而，分支模式对转录变化的反应非常缓慢，分支增加并不影响α-淀粉酶生产率。通过免疫荧光对存在于细胞壁中的α-淀粉酶进行了染色，并讨论了顶端数量与酶分泌之间的关系。
