α-Acetolactate Oversynthesis from Glucose in a Diacetyl Producer Lactococcus lactis ssp. lactis bv. diacetylactis B2103, a Natural Mutant Deprived of α-Acetolactate Decarboxylase

Автор: V.M. Serebrennikov, L.N. Kotova, and A.V. Glazunov

Страница: 24-38

α-Acetolactate Oversynthesis from Glucose in a Diacetyl Producer Lactococcus lactis ssp. lactis bv. diacetylactis B2103, a Natural Mutant Deprived of α-Acetolactate Decarboxylase

Biotekhnologiya, 2013, N 4, P. 24-38

UDC 577.151.52.547.442

Section:  “Producers, Biology, Selection, and Gene Engineering”

V.M. Serebrennikov,  L.N. Kotova,  and  A.V. Glazunov ^*

The State Research Institute for Genetics and Selection of Industrial Microorganisms,  117545, Moscow Russia

e-mail:  glasunov@genetika.ru

The effect of oxygen supply rate on the activity of pyruvate metabolic pathways and their end products (lactate-dehydrogenase (LDH), pyruvate-formate-lyase (PFL), pyruvate-dehydrogenase (PDH) and acetolactate-synthase (ALS) pathways) in Lactococcus lactis ssp. lactis bv. diacetylactis B2103/74 strain has been investigated. In was found out that this culture, apart from inactivated α-acetolactate decarboxylase, possesses a unique natural capacity of oversynthesizing α-acetolactate (AL) up to 25—28 mM. The search for analogous strains in the diacetilicus bv. showed that this evidence is relatively infrequent; only one culture (VKPM 7590) was shown to have the same capacity. However, unlike the B2103/74 strain, the 7590 culture has an active α-acetolactate decarboxylase, and therefore, it is only able to produce acetoin. The oversynthesis of AL was observed at intense aeration (K_La ≥90—120 h^–1); medium composition played a decisive role in the process. It was shown that a powerful shift of a part of the pyruvate flow from the LDH- to PDH- and ALS-pathway underlies the evidence of LA oversynthesis, and due a restricted throughout capacity of the PDH-pathway, all the metabolism of the additional pyruvate supplied from the LDH-pathway proceeded exclusively through the ALS- avoiding the PDH-pathway. The shift of the pyruvate metabolism from the LDH- to PDH- and ALS-pathways  in the B2103/74 culture is associated with the initiation of the oxidase reaction that reduces oxygen to H₂O and therefore overshoots for this purpose NADH from LDH. The specific manifestation of this reaction in the B2103/74 and 7590 cultures that resulted in a deep rearrangement of all pyruvate metabolism for the production of α-acetolactate is owing to the occurrence of a superactive oxidase system that shifts 75—80% of the NADH flow from LDH to the oxidase pathway for NAD⁺ regeneration. The origin of this superoxidase system is unknown. It is suggested that it can be close in structure to a simplest membrane-built electron-transport chain.

Key words:  acetoin,  α-acetolactate,  diacetyl,  lacticacid bacteria,  NADH-oxidase.

The full English version of the article was published in “Applied Biochemistry and Microbiology”, 2014, Vol.50, Issue 7, pp. 689-700 as V. M. Serebrennikov, L. N. Kotova, A. V. Glazunov “α-Acetolactate overexpression from glucose in the diacetyl producer Lactococcus lactis ssp. lactis bv. diacetylactis B2103, a natural mutant lacking α-acetolactate decarboxylase”.

It is contained at the SpringerLink website:  http://link.springer.com/article/10.1134/S0003683814070059

DOI: 10.1134/S0003683814070059

02.04.2015, 1744 просмотра.