A Role of Population Heterogeneity and pH Factor in Natural α-Acetolactate Supersynthesis in a Diacetyl Producer, Lactococcus lactis ssp. lactis bv. diacetylactis B2103/74

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

Страница: 28-38

A Role of Population Heterogeneity and pH Factor in Natural α-Acetolactate Supersynthesis in a Diacetyl Producer, Lactococcus lactis ssp. lactis bv. diacetylactis B2103/74

Biotekhnologiya, 2015, N 4, P. 28-38

UDC 577.151.52.547.442

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

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

The State Research Institute for Genetics and Selection of Microorganisms (GosNIIgenetika),  117545, Moscow Russia

e-mail:  glasunov@genetika.ru

The effect of the population heterogeneity and medium pH on the found out by us supersynthesis of α-acetolactate (AL) by the L. lactis bv. diacetyllactis B2103/74 culture has been investigated. The nature of an enzyme system that is responsible for this effect due to lactate dehydrogenase essentially blocking by intercepting up to 80% NADH from it and was indicated as hemin-independent electron-transferring system (HIETS) is unknown. It was shown that the effect was disguised by the culture heterogeneity which was the most pronounced at neighboring to neutral pH values 6.1—6.5. It was established that at least three types of dissociants with different HIETS and, consequently, AL levels occurred in the population: active dissociant (AL accumulation up to 30 mM); inactive dissociant that lost HIETS activity (AL content of no more than 3 mM); and dissociant with moderate activity (AL content 15—17 mM). It was demonstrated that HIETS played a major part in the whole pyruvate metabolism at various pH and finally in the AL supersynthesis. For instance, at pH =7.0, the effect of supersynthesis failed to be observed due to the HIETS low activity, and the pyruvate metabolism proceeded by the homolactic pathway. However, at pH 5.3—6.5, the HIETS activity was so high that it permitted the system to take over a function of the major regulator of the redox NAD⁺/NADH balance leaving the minor part to LDH. The productivities of LDH and acetolactate-synthase pathways depended on the HIETS activity at various pH values, whereas that of the pyruvatedehydrogenase pathway was a straight function of external pH. The latter was rather high in the close to neutral pH area (6.0—6.5) and was significantly lower in the neutral (pH=6.0—6.5) and light-acidic (pH≤6.0) zones.

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

06.11.2015, 1341 просмотр .