Applications of one-Step environmentally-friendly fermentation method to produce fumaric acid with immobilized Rhizopus arrhizus in stirred-tank reactor

The traditional two-step cultivation mode for fungal cultivation is commonly divided into the seed stage (usually 24 to 48 h) and the production stage (usually 96 to 144 h). The use of two stages prolongs the total production cycle and generates excess wastewater. In this work, an efficient and environmentally friendly one-step fermentation method was applied for the production of fumaric acid by immobilized Rhizopus arrhizus in a stirred-tank reactor. The nitrogen source content and the agitation speed of the reactor were optimized as the two critical factors in the one-step fermentation process; the fumaric acid production of 51 g/L with a yield of 0.42 g/g glucose was comparable with the product from the traditional two-step fermentation process. Furthermore, the total production cycle was shortened to 96 h, and the amount of wastewater was reduced due to the avoidance of the seed culture process. Thus, utilization of the one-step fermentation method to produce fumaric acid was shown to be preferable feasibility and environmental-friendliness. This is a promising method for industrial production of fumaric acid and other high-value biochemicals by fungus.