초록
<P>Different engineered organisms have been used to produce L-lactate. Poor yields of lactate at low pH and expensive downstream processing remain as bottlenecks. <I>Aspergillus niger</I> is a prolific citrate producer and a remarkably acid tolerant fungus. Neither a functional lactate dehydrogenase (LDH) from nor lactate production by <I>A</I>. <I>niger</I> is reported. Its genome was also investigated for the presence of a functional <I>ldh</I>. The endogenous <I>A</I>. <I>niger</I> citrate synthase promoter relevant to <I>A</I>. <I>niger</I> acidogenic metabolism was employed to drive constitutive expression of mouse lactate dehydrogenase (<I>mldhA</I>). An appraisal of different branches of the <I>A</I>. <I>niger</I> pyruvate node guided the choice of <I>mldhA</I> for heterologous expression. A high copy number transformant C12 strain, displaying highest LDH specific activity, was analyzed under different growth conditions. The C12 strain produced 7.7 g/l of extracellular L-lactate from 60 g/l of glucose, in non-neutralizing minimal media. Significantly, lactate and citrate accumulated under two different growth conditions. Already an established acidogenic platform, <I>A</I>. <I>niger</I> now promises to be a valuable host for lactate production.</P>