Fumaric Acid Fermentation by Rhizopus oryzae with Integrated Separation Technologies

Fumaric acid is an important specialty chemical with wide applications as a food acidulant and as the chemical feedstock for the production of resins, plasticizers, and miscellaneous industrial products. Currently, fumaric acid is produced through a petroleum-based chemical method. Fungal fermentation provides a promising alternative method due to its advantages in environmental friendliness and availability of widespread renewable biomass feedstock.;However, conventional fumaric acid fermentation processes suffer from low product yield, low productivity, and high production cost, whereas the competing chemical production methods are currently more economical. Therefore, the goal of this research was to develop effective and economic fermentation and recovery methods for improved fumaric acid production by Rhizopus oryzae. One of the major technical challenges is to control the fungal morphology and physiology for the overproduction of fumaric acid in a sustainable and scalable way.;First, an effective fermentation process with good morphology control was developed using soybean meal hydrolysate as the nitrogen source for cell growth and fumaric acid production by R. oryzae. Uniformly dispersed mycelial clumps with a diameter of ∼0.1 mm were formed with enhanced subsequent fumaric acid production. The fermentation reached a product titer of 50.2 g/L with yield of 0.72 g/g glucose. SMH with a high protein content was demonstrated as a good nitrogen source and the formation of protein precipitate acted as the immobilization carriers for cells. The solid-phase protein also provided a novel method for slow/controlled release that allowed the utilization of the nitrogen source by cells for an extended period without losing cell activity.;The fermentation was then studied in a 5-L stirred tank bioreactor (STB) and the results also showed that using SMH as the nitrogen source improved fumaric acid production with increased yield and productivity compared to urea. Aeration with air containing 16.7% CO2 increased the productivity by 76% and product titer by 13%. To improve the productivity, in situ product recovery by coupling the fermentation with an ion exchange column for fumaric acid adsorption was investigated. A strong-basic anion exchange resin IRA900 was selected due to its high adsorption capacity at fermentation-favored pH of 5.0, and high selectivity against byproducts. The adsorption isotherm and the mechanism involved were investigated. A preliminary study showed that fermentation with intermittent in situ recovery enhanced product yield by 25% and productivity by 59%. In order to recover the low-concentration fumaric acid >98%. Compared to the conventional recovery process using precipitation, although this new process require additional capital investment, with the reduced operational costs and enhanced the recovery yield it is economically and environmentally favorable with good potential for industrial application.