Molecular cloning and expression of Enterobacter aerogenes α-acetolactate decarboxylase in pyruvate decarboxylase-deficient Saccharomyces cerevisiae for efficient 2,3-butanediol production

alpha-Acetolactate decarboxylase (ALDC) catalyzes the conversion of alpha-acetolactate into acetoin, a precursor of 2,3-butanediol (2,3-BD). In this study, we overexpressed the genes coding for various ALDCs from natural 2,3-BD producing bacteria in recombinant Saccharomyces cerevisiae SB strains with two essential enzymes for 2,3-BD production (alpha-acetolactate synthase and 2,3-BD dehydrogenase) and without pyruvate decarboxylase (PDC) activity. Expression of ALDCs from Bacillus subtilis and Enterobacter aerogenes gave 1.3-1.5 times higher 2,3-BD productivities than those from Klebsiella pneumoniae and Klebsiella oxytoca oxytoca. Kinetic analysis of purified ALDCs revealed that E. aerogenes ALDC exhibited an 1.7 fold higher k(cat)/K-m (22.9 +/- 0.2 mM(-1) s(-1)) than B. subtilis ALDC (13.3 +/- 4.1 mM(-1)s(-1)). In fed-batch fermentations by intermittent addition of a concentrated glucose solution, the SB-Ea strain overexpressing E. aerogenes ALDC produced 132.4 g/L of 2,3-BD with a yield of 0.34g 2,3-BD/g glucose and 0.41 g/L h productivity, which were 30% and 25% higher than those of the BD4 strain expressing B. subtilis ALDC. It was concluded that E. aerogenes ALDC was the most effective enzyme among four bacterial ALDCs for improving 2,3-BD production in PDC-deficient S. cerevisiae. (C) 2015 Elsevier Ltd. All rights reserved.