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.…”

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.…”