Biotechnological production of Itaconic acid

Background and Objective

Itaconic acid is produced biotechnological with the fungus Aspergillus terreus using sugar as substrate. Although this process is carried out industrial more than 50 years, the maximum attainable concentrations of 90 g/L are significantly below those of comparable processes such as citric acid production. The costs of the biotechnological production of itaconic acid are mainly limited by low product concentration, low productivity and low yields. Therefore the main goal of the current work is a process optimization using intelligent, innovative strategies for the biotechnological production of itaconic acid.

Approach

At first a scale down of the fermentation process to µL scale should be carried out. This would be a requirement for an efficient subsequent media optimization. More fermentation parameters should be varied at bioreactor scale.

Data and Methods

A reduction of the scale was performed in microtiter plates, in which subsequently a media optimization was carried out. In a 400 mL and 1 L bioreactor system in particular the influence of the pH value was examined for the product formation.

Results

During the project period, a simple system was established with low standard deviations in the μL scale for mutations and a process optimization of biotechnological itaconic acid production with the filamentous fungus Aspergillus terreus. It shows very good correlation to the cultivation in shake flasks.

Furthermore, a new method of producing spores was established. Conducting a pH shift induced the formation of submerged spores. When using the submerged spores as inoculum for cultivation, the lag phase is shortened, the productivity is comparable to previously used spores from surface cultures, and the duration of cultivation is reduced.

The unique pH shift also shows a positive effect on the final itaconic acid concentration (110 g/L itaconic acid after 7.6 days). Performing a pH shift, with subsequent regulation of the pH, results in a significant increase of the final concentration to 146.1 g/L itaconic acid after 12.6 days cultivation with a yield of 0.59 (w/w). This is an increase in the final concentration of 68 % compared to the published literature. In a final experiment, the previously optimized parameters for the itaconic acid production were combined. Here, after 4.7 days of cultivation, a final concentration of 129.3 g/L itaconic acid was reached. This corresponds to a productivity of 1.15 g/L/h. The yield was with 0.58 (w/w) higher compared to the yield of the reference with 0.53 (w/w). The project has shown that the transfer to μL scale is very successful feasible and contrary to the current literature there is no need for a phosphate limitation during itaconic acid production. Compared to the initial situation, 90 g/L itaconic acid after 7 days, the final concentration was significantly increased with a simultaneous reduction of the fermentation time, so that the knowledge gained in the project is of high scientific and industrial value.