Enzymatic Removal of Diacetyl from Beer

Abstract

Diacetyl removal from beer was studied with whole cells and crude enzyme extracts of yeasts and bacteria. Cells of Streptococcus diacetilactis 18-16 destroyed diacetyl in solutions at a rate almost equal to that achieved by the addition of whole yeast cells. Yeast cells impregnated in a diatomaceous earth filter bed removed all diacetyl from solutions percolated through the bed. Undialyzed crude enzyme extracts from yeast cells removed diacetyl very slowly from beer at its normal pH (4.1); at a pH of 5.0 or higher, rapid diacetyl removal was achieved. Dialyzed crude enzyme extracts from yeast cells were found to destroy diacetyl in a manner quite similar to that of diacetyl reductase from Aerobacter aerogenes, and both the bacterial and the yeast extracts were stimulated significantly by the addition of reduced nicotinamide adenine dinucleotide (NADH). Diacetyl reductase activity of four strains of A. aerogenes was compared; three of the strains produced enzyme with approximately twice the specific activity of the other strain (8724). Gel electrophoresis results indicated that at least three different NADH-oxidizing enzymes were present in crude extracts of diacetyl reductase. Sephadex-gel chromotography separated NADH oxidase from diacetyl reductase. It was also noted that ethyl alcohol concentrations approximately equivalent to those found in beer were quite inhibitory to diacetyl reductase.

Characterization of partially purified alcohol dehydrogenase from Rhodococcus sp. strain GK1

“…Some alcohol dehydrogenases catalyse the reduction of diacetyl (2,3 butanediol) to acetoin. These diacetyl reductase enzymes could be used for the removal of diacetyl causing off-flavour in beer (Tolls et al 1970), and for the enzymic determination of this compound (Gibson et al 1991) and methylketones in food.…”

Continuous Fermentation of Glucose Solutions

“…A similar concept for the removal of a-dketones from beer has also been described in the literature. 24 The patent specification implies the suitability of the process for the production of beer.10 Subsequent investigations by Narziss & Hellich17-18 indicated that the beer so produced required a 'conditioning' period in the presence of yeast for 3-4 days. This conditioning period is required to remove diacctyl from the beer.…”

Study of acetoin reductase from Kluyveromyces marxianus

“…Acetoin (3-hydroxy-2-butanone) is a physiological intermediate in yeasts formed by the reduction of diacetyl (2,3-butanedione) (Liebs et al 1969) or as a side product from the valineleucine biosynthetic pathway via a-acetolactate (Heidlas & Tressl 1990a). It is a desirable compound in various fermented dairy products, but its presence in beer, wines as well as in citrus juices is objectionable since the chemical or enzymatic oxidation of diacetyl causes serious off flavours (Tolls et al 1970).…”