초록
<B>Abstract</B>Background<P><I>Ustilago cynodontis</I> ranks among the relatively unknown itaconate production organisms. In comparison to the well-known and established organisms like <I>Aspergillus terreus</I> and <I>Ustilago maydis</I>, genetic engineering and first optimizations for itaconate production were only recently developed for <I>U. cynodontis,</I> enabling metabolic and morphological engineering of this acid-tolerant organism for efficient itaconate production. These engineered strains were so far mostly characterized in small scale shaken cultures.</P>Results<P>In pH-controlled fed-batch experiments an optimum pH of 3.6 could be determined for itaconate production in the morphology-engineered <I>U. cynodontis</I> Δ<I>fuz7.</I> With <I>U. cynodontis ∆fuz7</I><SUP><I>r</I></SUP><I>∆cyp3</I><SUP><I>r</I></SUP><I>P</I><I>etef</I><I>mttA P</I><I>ria1</I><I>ria1</I>, optimized for itaconate production through the deletion of an itaconate oxidase and overexpression of rate-limiting production steps, titers up to 82.9 ± 0.8 g L<SUP>−1</SUP> were reached in a high-density pulsed fed-batch fermentation at this pH. The use of a constant glucose feed controlled by in-line glucose analysis increased the yield in the production phase to 0.61 gITA gGLC<SUP>−1</SUP>, which is 84% of the maximum theoretical pathway yield. Productivity could be improved to a maximum of 1.44 g L<SUP>−1</SUP> h<SUP>−1</SUP> and cell recycling was achieved by repeated-batch application.</P>Conclusions<P>Here, we characterize engineered <I>U. cynodontis</I> strains in controlled bioreactors and optimize the fermentation process for itaconate production. The results obtained are discussed in a biotechnological context and show the great potential of <I>U. cynodontis</I> as an itaconate producing host.</P>