Production of diacetyl by metabolically engineered Enterobacter cloacae

Abstract

Diacetyl, a high value product that can be extensively used as a food ingredient, could be produced from the non-enzymatic oxidative decarboxylation of α-acetolactate during 2,3-butanediol fermentation. In this study, the 2,3-butanediol biosynthetic pathway in Enterobacter cloacae subsp. dissolvens strain SDM, a good candidate for microbial 2,3-butanediol production, was reconstructed for diacetyl production. To enhance the accumulation of the precursor of diacetyl, the α-acetolactate decarboxylase encoding gene (budA) was knocked out in strain SDM. Subsequently, the two diacetyl reductases DR-I (gdh) and DR-II (budC) encoding genes were inactivated in strain SDM individually or in combination to decrease the reduction of diacetyl. Although the engineered strain E. cloacae SDM (ΔbudAΔbudC) was found to have a good ability for diacetyl production, more α-acetolactate than diacetyl was produced simultaneously. In order to enhance the nonenzymatic oxidative decarboxylation of α-acetolactate to diacetyl, 20 mM Fe3+ was added to the fermentation broth at the optimal time. In the end, by using the metabolically engineered strain E. cloacae SDM (ΔbudAΔbudC), diacetyl at a concentration of 1.45 g/L was obtained with a high productivity (0.13 g/(L·h)). The method developed here may be a promising process for biotechnological production of diacetyl.

Role of lactic acid bacteria on the yogurt flavour: A review

“…[83,89] For instance, although several metabolic engineering strategies have been designed to improve diacetyl production by LAB, the effects are limited, as diacetyl is an intermediate metabolite, and its synthesis and decomposition are controlled by many pathways and influenced by redox balance and chemical modifications. [90] A genome-scale metabolic model that includes carbon and nitrogen metabolism and flavour-forming pathways is crucial for understanding and designing metabolic engineering strategies. [88] The combination of these strategies and the availability of numerous genetic tools for these microorganisms will help reroute the metabolic flux towards the efficient accumulation of the desired flavour compounds.…”

Industrial Production of 2,3-Butanediol from the Engineered Corynebacterium glutamicum

“…C. glutamicum is known as natural 2,3-BDO producer [3], but lacks the α-acetolactate decarboxylase that plays a key role in efficient 2,3-BDO production, according to pathway information from online databases such as the Kyoto Encyclopedia of Genes and Genomes (KEGG). Wild-type C. glutamicum produces 2,3-BDO via a diacetyl intermediate synthesized by a spontaneous reaction from α-acetolactate, but the driving force of this spontaneous reaction is weak when compared with the strong reaction catalyzed by α-acetolactate decarboxylase [16]. Therefore, to enhance the 2,3-BDO-producing ability of C. glutamicum, we introduced budA encoding the acetolactate decarboxylase from K. pneumoniae, a powerful 2,3-BDO producer.…”

Synthesis of (3R)-acetoin and 2,3-butanediol isomers by metabolically engineered Lactococcus lactis

“…Formation of the specific isomers of 2,3-BDO involves the use of specific BDHs (butanediol dehydrogenases) and which isomers that are formed also depends on the stereoisomeric form of acetoin32333435. (3 R )-acetoin can be converted to either m-BDO or R-BDO and (3 S )-acetoin can be converted to m-BDO and S-BDO.…”