Itaconate Production from Crude Substrates with U. maydis: Scale-up of an Industrially Relevant Bioprocess.

BACKGROUND: Industrial by-products accrue in most agricultural or food-related production processes, but additional value chains have already been established for many of them. Crude glycerol has a 60% lower market value than commercial glucose, as large quantities are produced in the biodiesel industry, but its valorisation is still underutilized. Due to its high carbon content and the natural ability of many microorganisms to metabolise it, microbial upcycling is a suitable option for this waste product. RESULTS: In this work, the use of crude glycerol for the production of the value-added compound itaconate is demonstrated using the smut fungus Ustilago maydis. Starting with a highly engineered strain, itaconate production from an industrial glycerol waste stream was quickly established on a small scale, and the resulting yields were already competitive with processes using commercial sugars. Adaptive laboratory evolution resulted in an evolved strain with a 72% increased growth rate on glycerol. In the subsequent development and optimisation of a fed-batch process on a 1.5-2 L scale, the use of molasses, a side stream of sugar beet processing, eliminated the need for other expensive media components such as nitrogen or vitamins for biomass growth. The optimised process was scaled up to 150 L, achieving an overall titre of 72 g L- 1, a yield of 0.34 g g- 1, and a productivity of 0.54 g L- 1 h- 1. CONCLUSIONS: Pilot-scale itaconate production from the complementary waste streams molasses and glycerol has been successfully established. In addition to achieving competitive performance indicators, the proposed dual feedstock strategy offers lower process costs and carbon footprint for the production of bio-based itaconate.

Influence of L-isoleucine and pantothenate auxotrophy for L-valine formation in Corynebacterium glutamicum revisited by metabolome analyses.

The effect of different amounts of supplemented L-isoleucine and pantothenate has been analysed with the auxotrophic strain Corynebacterium glutamicum DeltailvA DeltapanB, showing that the final biomass concentration of this preliminary L-valine production strain can be controlled by the amount of added L-isoleucine. One gramme cell dry weight is formed from 48 micromol L-isoleucine. Different amounts of available pantothenate affect the intracellular pyruvate concentration. By limiting pantothenate supplementation from 0.8 to 0.1 microM, a 35-fold increase of cytoplasmic pyruvate up to 14.2 mM can be observed, resulting in the increased formation of L-valine, L-alanine and organic acids in the presence of low pantothenate concentrations. These findings can be used to redirect the carbon flux from glycolysis via pyruvate to the TCA cycle towards the desired product L-valine.