Influence of culture aeration on the cellulase activity of Thermobifida fusca
Influence of culture aeration on the cellulase activity of Thermobifida fusca
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DOI：
10.1007/s00253-009-2155-9
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发表时间：
2010-01-01
影响因子：
5
通讯作者：
Fong, Stephen S.
中科院分区：
文献类型：
--
作者：
Deng, Yu;Fong, Stephen S.
目前，阻碍纤维素生物燃料有效生产的障碍之一是纤维素对水解的抑制性。在微生物中天然发现了多种纤维素酶，其可潜在地用于有效地将纤维素水解成可发酵糖。在这项研究中，使用中度嗜热、好氧和纤维素分解微生物菌棕色热裂菌研究了影响纤维素酶活性的现象学和机理参数。进行了两组主要的实验，以（1）研究烧瓶中与生物反应器中相比生长的机理差异，以及（2）使用一系列生物反应器实验研究影响纤维素酶活性的细胞培养参数。比纤维素酶和比内切葡聚糖酶的活动被发现是更高的生物反应器相比，烧瓶生长。18个纤维素酶相关基因的信使RNA转录水平和细胞内ATP水平的测量表明，测得的酶活性可能更多地受到转录后能量学的影响，而不是转录调控。通过描述使用生物反应器的培养物通气和搅拌速度的影响，发现纤维素酶活性随着通气的增加和搅拌速度的增加（最高K（I）a）而增加，其中在所测试的最高搅拌速度（400 rpm）下细胞生长降低的折衷。总之，这些结果暗示了通气和氧化呼吸之间的联系，其导致增加的ATP，从而允许增加的纤维素酶合成作为对总体纤维素酶活性的主要限制。
Currently, one of the hurdles hindering efficient production of cellulosic biofuel is the recalcitrant nature of cellulose to hydrolysis. A wide variety of cellulase enzymes are found natively in microorganisms that can potentially be used to effectively hydrolyze cellulose to fermentable sugars. In this study, phenomenological and mechanistic parameters affecting cellulase activity were studied using the moderately thermophilic, aerobic, and cellulolytic microogainsm Thermobifida fusca. Two major sets of experiments were conducted to (1) study the mechanistic differences in growth in a flask compared to a bioreactor and (2) study the cell culture parameters influencing cellulase activity using a series of bioreactor experiments. Specific cellulase and specific endoglucanase activities were found to be higher in the bioreactor as compared to flask growth. Measurements of messenger RNA transcript levels of 18 cellulase-related genes and intracellular ATP levels indicated that measured enzyme activity was likely more influenced by post-transcriptional energetics rather than transcriptional regulation. By delineating the effects of culture aeration and stir speed using a bioreactor, it was found that cellulase activity increased with increasing aeration and increasing stir speeds (highest K (l) a) with a tradeoff of decreased cellular growth at the highest stir speeds tested (400 rpm). Overall, these results allude to a connection between aeration and oxidative respiration that lead to increased ATP allowing for increased cellulase synthesis as the primary constraint on overall cellulase activity.