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Indexed by:期刊论文

Date of Publication:2009-01-01

Journal:WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY

Included Journals:SCIE、EI、Scopus

Volume:25

Issue:1

Page Number:57-64

ISSN No.:0959-3993

Key Words:Enterobacter aerogenes; Diacetyl accumulation; Fermentation; Diacetyl

Abstract:A mutant designated as UV-3 was obtained from wild-type Enterobacter aerogenes 10293 through u.v. radiation. The activities of alpha-acetolactate decarboxylase (Ald), lactate dehydrogenase (Ldh) and diacetyl reductase (Dr) in UV-3 were strongly attenuated, with the lowest activities at pH 7.0-7.5, and temperature between 36 and 39c degrees. Compared to the wild-type, the yield of diacetyl by UV-3 was increased 18.7-fold, up to 1.05 +/- 0.01 g l(-1). Acetoin and ethanol productions were decreased by 48.4 and 71.4%, respectively, but acetate yield was increased by 34.6%. Optimum medium for diacetyl production by UV-3 contained 10% glucose, 0.5% peptone, 0.5% yeast extract powder, 0.01% (NH(4))(2)SO(4), 0.1% citric acid, 0.2% MnSO(4) and 0.2% MgSO(4), and this was determined by one-factor-at-a-time approach. Data from the five level central composite designs demonstrated that initial pH of 7.0, temperature of 37 degrees C and rotational speed of 180 rev/min were optimum processing parameters for diacetyl production. The maximum yield of diacetyl could reach 1.35 g l(-1) in a 5-l bioreactor. These results showed an enhancement of the non-enzymatic oxidative decarboxylation of alpha-acetolactate and a decrease in the activities of Ald, Ldh and Dr as a consequence of diacetyl accumulation in UV-3.