Erythritol production by the saprobe Trichoderma reesei: screening and optimization using Design of Experiments to better understand the effect of nitrogen source, carbon source, pH and temperature.

Abstract

Erythritol is a four-carbon polyol, widely occurring in nature in mushrooms and fruits. It is also found in fermented food and drinks such as soy sauce, wine, or beer due to its production by fungi and some lactic acid bacteria. Its specific properties make it a sweetener of growing interest. Erythritol is reported to have minor side effects on the digestive tracks. Additionally, no effect on sugar or insulin level has been reported, nor has it any impact on the gut microbiota, making erythritol one of the safest sweeteners reported so far. But despite all its advantages, erythritol use is still limited in the food industry due to its high manufacturing cost. The high cost of erythritol is partially due to the use of glucose as a substrate. At the industrial scale, the leading producers of erythritol are osmophilic yeasts, mainly Moniliella pollinis. They use glucose, obtained by hydrolyzing corn or potato starch, and metabolize it into erythritol. Strategies to improve erythritol manufacturing have been oriented around four axes: improve producer strains by genetic engineering, develop the use of cheaper substrates, better understand polyols metabolism and optimize the manufacturing process. Due to the European regulation on GMOs, interest has been growing in producing erythritol from non-GMO strains. If strains cannot be engineered, the main remaining axes for improvement are understanding erythritol production better, improving and optimizing the production process, and finding cheaper substrates. In this logic, we worked on developing a production process with Trichoderma reesei, a saprobe, using agro-industrial waste as substrates. The presented work focused on using Design of Experiments (DoE) to screen the effect of 4 process parameters: nitrogen source, carbon source, pH, and temperature. An optimum in the tested range was also proposed. This work also brought hypotheses on how these parameters modify polyol production