Developmental and environmental influences in the production of a single NAD-dependent fermentative alcohol dehydrogenase by the zygomycete Mucor rouxii

Abstract

A soluble NAD-dependent alcohol dehydrogenase (ADH) activity was detected in mycelium and yeast cells of wild-type Mucor rouxii. In the mycelium of cells grown in the absence of oxygen, the enzyme activity was high, whereas in yeast cells, ADH activity was high regardless of the presence or absence of oxygen. The enzyme from aerobically or anaerobically grown mycelium or yeast cells exhibited a similar optimum pH for the oxidation of ethanol to acetaldehyde ( approximately pH 8.5) and for the reduction of acetaldehyde to ethanol (approximately pH 7.5). Zymogram analysis conducted with cell-free extracts of the wild-type and an alcohol-dehydrogenase-deficient mutant strain indicated the existence of a single ADH enzyme that was independent of the developmental stage of dimorphism, the growth atmosphere, or the carbon source in the growth medium. Purified ADH from aerobically grown mycelium was found to be a tetramer consisting of subunits of 43 kDa. The enzyme oxidized primary and secondary alcohols, although much higher activity was displayed with primary alcohols. K(m) values obtained for acetaldehyde, ethanol, NADH(2), and NAD(+) indicated that physiologically the enzyme works mainly in the reduction of acetaldehyde to ethanol.

Ethanol production from hexoses, pentoses, and dilute-acid hydrolyzate by

“…Research activities on M. indicus have mainly been conducted in connection with the physiology of its 1567 dimorphism, with the growth in the yeast-like form or as filamentous mycelium [8][9][10][11][12][13]. The fungus has also been studied with respect to the production from its mycelia of chitin and its deacetylated derivative chitosan.…”

Fungal Alcohol Dehydrogenases: Physiological Function, Molecular Properties, Regulation of Their Production, and Biotechnological Potential

“…In Mucor , anaerobic yeast is associated with high rates of ethanol production [ 83 ], which correlate with higher levels of ADH activity [ 84 ]. M. rouxii shows elevated ADH activity in mycelium cells grown in the absence of oxygen, whereas in yeast cells, ADH activity is not dependent on the presence or absence of oxygen [ 85 ]. Under aerobic conditions, in the presence of glucose, M. lusitanicus grows as mycelium and produces significant amounts of ethanol [ 33 ].…”

Chemo- and stereoselective reduction of β-keto esters by spores and various morphological forms of Mucor rouxii

“…Mucor rouxii is a dimorphic fungus that can grow as a cenocytic mycelium under aerobic conditions or as yeastlike cells under anaerobiosis and high glucose levels in the culture medium. There are some reports in the literature characterizing biochemically, but not biotechnologically, oxidoreductase activities from different species of Mucor: a dihydroxyacetone reductase from Mucor javanicus [15]; a NAD-dependent glutamate dehydrogenase in Mucor racemosus [16]; a NADPH-dependent carbonyl reductase in Mucor ambiguus, with high specificity towards conjugated polyketones [17]; and very recently a NAD-dependent alcohol dehydrogenase in Mucor rouxii, which seems to work physiologically in the reduction of acetaldehyde to ethanol [18].…”