Betaine Tripled the Volumetric Productivity of d(-)-lactate byEscherichia coliStrain SZ132 in Mineral Salts Medium

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Abstract

Osmotic stress restricts glycolytic flux, growth (rate and yield), d-lactate productivity, and d-lactate tolerance in Escherichia coli B strain SZ132 during batch fermentation in mineral salts medium with 10% (w/v) sugar. Addition of 1 mm betaine, a non-metabolized protective osmolyte, doubled cell yield, increased specific productivity of d-lactate and glycolytic flux by 50%, and tripled volumetric productivity (from 8.6 to 25.7 mmol l-1 h-1; 0.8 to 2.3 g l-1 h-1). Glycolytic flux and specific productivity in mineral salts medium with betaine exceeded that in Luria broth, substantially eliminating the need for complex nutrients during d-lactate production. In mineral salts medium supplemented with betaine, SZ132 produced approximately 1 mol d-lactate (90 g) per 100 g sugar (glucose or sucrose).

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