EFFECT OF DILUTION RATE AND CARBON AVAILABILITY ON BIFIDOBACTERIUM BREVE FERMENTATION
EFFECT OF DILUTION RATE AND CARBON AVAILABILITY ON BIFIDOBACTERIUM BREVE FERMENTATION
复制标题
DOI：
10.1007/s002530050070
复制
发表时间：
1994-02-01
影响因子：
5
通讯作者：
MACFARLANE, GT
中科院分区：
文献类型：
--
作者：
DEGNAN, BA;MACFARLANE, GT
短双歧杆菌NCFB 2257在葡萄糖限制和氮（N）限制的恒化器中以0.04至0.60 h（-1）的稀释率（D）生长，以研究营养可利用性对碳水化合物代谢的影响。结果表明，无论营养限制的形式如何，D对发酵产物的形成几乎没有影响。然而，在发酵产物的分布中观察到显著差异，这归因于葡萄糖的可用性。在葡萄糖限制培养中，甲酸盐和乙酸盐是代谢的主要终产物。在这些生长条件下从未检测到乳酸盐。相反，当葡萄糖过量时，主要形成乳酸和乙酸，而不产生甲酸。这些结果可以用丙酮酸盐的代谢命运来解释，丙酮酸盐可以通过磷酸分解分解为乙酰磷酸和甲酸盐而异化，或者可以还原为乳酸盐。进行了酶学研究以建立调节丙酮酸代谢的机制。这些数据表明，控制不行使通过调节乳酸脱氢酶（LDH），磷酸果糖激酶或乙醇脱氢酶的合成和活性。然而，可能存在LDH和磷酸化酶对丙酮酸的竞争，这将分别决定产生的乳酸和甲酸的水平。这些结果证明了B的代谢灵活性。短，优先使用乳酸作为电子汇在N-有限的增长，而在能量限制下，碳流是针对乙酰磷酸，以最大限度地提高ATP的合成。
Bifidobacterium breve NCFB 2257 was grown in glucose-limited and nitrogen (N)-limited chemostats at dilution rates (D) from 0.04 to 0.60 h(-1), to study the effect of nutrient availability on carbohydrate metabolism. The results showed that D had little effect on fermentation product formation, irrespective of the form of nutrient limitation. However, marked differences were observed in the distribution of fermentation products, that were attributable to glucose availability. In glucose-limited cultures, formate and acetate were the principal end-products of metabolism. Lactate was never detected under these, growth conditions. In contrast, lactate and acetate were mainly formed when glucose was in excess, and formate was not produced. These results are explained by the metabolic fate of pyruvate, which can be dissimilated by either phosphoroclastic cleavage to acetyl phosphate and formate, or alternatively, it may be reduced to lactate. Enzymic studies were made to establish the mechanisms that regulated pyruvate metabolism. The data demonstrated that control was not exercised through regulation of the synthesis and activity of lactate dehydrogenase (LDH), phosphofructokinase or alcohol dehydrogenase. It is possible however, that there was competition for pyruvate by LDH and the phosphoroclastic enzyme, which would determine the levels of lactate and formate produced respectively. These results demonstrate the metabolic flexibility of B. breve, which preferentially uses lactate as an electron sink during N-limited growth, whereas under energy-limitation, carbon flow is directed towards acetyl phosphate to maximise ATP synthesis.