Kinetic Modelling of the Coproduction Process of Fumaric and Malic Acids by Rhizopus arrhizus NRRL 1526

Abstract

The production of organic acids by biotechnological processes has experienced a notable impulse with the advent of first and second generation biorefineries and the need of searching for renewable and sustainable feedstock, such as biomass. Fumaric acid is a promising biomonomer for polyamide production and a well-known acidulant and preservative in food and feed industries. Malic acid is a well-known food acidulant with a high market share. The biotechnological Fumaric and Malic acid production via fungi of the Rhizopus genus is being explored nowadays as a process for the valorization of food and food-related waste to obtain food ingredients and key platform chemicals of the so-called biochemical biorefinery. In this work, a preliminary study is performed to find reproducible conditions for the production of the acids by Rhizopus arrhizus NRRL 1526 by controlling fungi morphology and inoculum conditions. Afterwards, several production runs are performed to obtain biomass, glucose, and acid concentration data at different processing time values. Finally, an unstructured, unsegregated model including a logistic-type equation for biomass and potential-type equations for the substrate and the products is fitted to experimental data. We find that the production of the organic acids is mainly non-associated with fungal growth.

Production of Fumaric Acid by Rhizopus arrhizus NRRL 1526: A Simple Production Medium and the Kinetic Modelling of the Bioprocess

“…In the present study, some process conditions selected by previous researchers were applied [7]. All experiments were performed at 34 • C and 200 rpm, with an initial spore concentration of 10 9 spores/L on the inoculum, using 100 mL non-baffled Erlenmeyer flasks with 20 mL of each culture medium with cellulose covers [7].…”

“…In the present study, some process conditions selected by previous researchers were applied [7]. All experiments were performed at 34 • C and 200 rpm, with an initial spore concentration of 10 9 spores/L on the inoculum, using 100 mL non-baffled Erlenmeyer flasks with 20 mL of each culture medium with cellulose covers [7]. To start each production run, the initial inoculum volume transferred to production medium was 10% v/v, using the inoculum culture obtained after 12 h in the aforementioned conditions.…”

“…To start each production run, the initial inoculum volume transferred to production medium was 10% v/v, using the inoculum culture obtained after 12 h in the aforementioned conditions. All experiments were performed in triplicate [7].…”

“…Although the acid is widely used as an acidulant in the food and feed industries [4], a promising industrial application is as chemical building block, being the raw material to obtain several resins and polyamides [4,5]. In recent years, new applications for this acid have been developed, such as a supplement for cattle feeding, reducing up to 70% methane emissions [6]; in new biopolymers; and as a crosslinker for packaging materials, providing more sturdiness and modifying swelling and mechanical behaviour of hydrogels [7,8]. In medicine, fumaric acid and its esters are used as an active ingredient against the skin disease psoriasis and multiple sclerosis (encephalomyelitis disseminata), a chronic inflammatory autoimmune disease of the nervous system [9,10].…”

“…These morphologies are an indicator of the metabolic and cellular states, influencing the fungal production profile [17]. In fact, fungal morphology can be controlled through certain process conditions such as agitation or aeration rates [17][18][19], spore initial concentration [7] or supplementary nitrogen sources [5]. This morphological growth generates certain technical problems such as low oxygen transfer or high broth viscosity, with the precise quantification of the viable biomass being very complex.…”