Rhizopus oryzae for Fumaric Acid Production: Optimising the Use of a Synthetic Lignocellulosic Hydrolysate

Abstract

The hydrolysis of lignocellulosic biomass opens an array of bioconversion possibilities for producing fuels and chemicals. Microbial fermentation is particularly suited to the conversion of sugar-rich hydrolysates into biochemicals. Rhizopus oryzae ATCC 20344 was employed to produce fumaric acid from glucose, xylose, and a synthetic lignocellulosic hydrolysate (glucose–xylose mixture) in batch and continuous fermentations. A novel immobilised biomass reactor was used to investigate the co-fermentation of xylose and glucose. Ideal medium conditions and a substrate feed strategy were then employed to optimise the production of fumaric acid. The batch fermentation of the synthetic hydrolysate at optimal conditions (urea feed rate 0.625mgL−1h−1 and pH 4) produced a fumaric acid yield of 0.439gg−1. A specific substrate feed rate (0.164gL−1h−1) that negated ethanol production and selected for fumaric acid was determined. Using this feed rate in a continuous fermentation, a fumaric acid yield of 0.735gg−1 was achieved; this was a 67.4% improvement. A metabolic analysis helped to determine a continuous synthetic lignocellulosic hydrolysate feed rate that selected for fumaric acid production while achieving the co-fermentation of glucose and xylose, thus avoiding the undesirable carbon catabolite repression. This work demonstrates the viability of fumaric acid production from lignocellulosic hydrolysate; the process developments discovered will pave the way for an industrially viable process.

Fumaric acid production from fermented oil palm empty fruit bunches using fungal isolate K20: a comparison between free and immobilized cells

“…Immobilization techniques have been widely explored to increase the possibility of a continuous fermentation process, as well as reuse microbial cells for several cycles on an industrial scale ( Naude & Nicol, 2017 ; Deng & Aita, 2018 ; Swart, Brink & Nicol, 2022 ) . The amount of FA produced after fermentation for 96 h with free and immobilized isolate K20 cells was 3.25 and 1.50 g/L, respectively.…”

Fumaric Acid Production by R. arrhizus NRRL 1526 Using Apple Pomace Enzymatic Hydrolysates: Kinetic Modelling

“…This effect could be explained by the accumulation of an intermediate metabolite, possibly malate, as the result of the deactivation of fumarase or other enzymes on the TCA reductive pathway [47,51] Other remarkable difference is the ethanol disappearance once its maximum is reached. As mentioned before, the Crabtree effect can be activated or not depending on the concentration of glucose and fructose, being the threshold concentration dependent on the sugar [40]. In fact, this effect can also be affected by the presence of inhibitory substances.…”

“…Ethanol evolution is of notable interest. In the bibliography it is widely reported how its production is linked to fungal growth, and when it stops, ethanol concentration starts decreasing, as a consequence of evaporation [30,39] and/or due to its consumption by the fungus after having produced it via the Crabtree effect [40]. This effect is reported to take place in different processes performed by certain species of fungi and yeasts.…”

“…This effect is reported to take Ethanol evolution is of notable interest. In the bibliography it is widely reported how its production is linked to fungal growth, and when it stops, ethanol concentration starts decreasing, as a consequence of evaporation [30,39] and/or due to its consumption by the fungus after having produced it via the Crabtree effect [40]. This effect is reported to take Regarding the experiment 2 (Figure 2), the use of both sugars combined in identical concentrations at zero time provides very close results to those obtained when we use only glucose.…”

Recent Advances in Miscanthus Macromolecule Conversion: A Brief Overview

“…The production of fumaric acid from glucose is a well-studied topic, whereas the option of using lignocellulosic hydrolyzates has received less attention. Swart et al [ 134 ] have recently explored the use of a synthetic lignocellulosic hydrolyzate (mixed glucose and xylose) for the production of fumaric acid with Rhizopus oryzae . The continuous fermentation with a low mixed glucose/xylose feeding rate allowed fumaric acid to be produced in a 0.735 g/g yield.…”