Unlocking nature's sweet secret for citric acid production from wood sugars: Evaluation of microbial strains and environmental impacts

This study investigates a novel approach by utilizing wood-derived sugars as a substrate for microbial citric acid (CA) production. Additionally, it examines the environmental implications through an ex-ante life cycle assessment (LCA). Various microbial strains including six yeast strains from the Yarrowia genus, three filamentous fungi strains from the Aspergillus genus, and eight bacterial strains were evaluated for their potential in CA production. The investigation primarily focused on optimizing citric acid production by considering various factors such as substrate concentrations, nitrogen levels, alcohols, surfactants, and the potential of non-commercial strains. The study yielded promising results, with the highest CA yields recorded as follows: 5.7 g/L from bacterial fermentation, 36.8 g/L from yeast fermentation, and 67.7 g/L from fungi fermentation. Furthermore, by applying an ex-ante LCA, the study assessed the environmental impact of citric acid production. Results indicated a significant reduction in environmental footprint when scaled up, with emissions decreasing from 235 to 585.8 kgCO2eq/kg at the laboratory scale to 4–6 kgCO2eq/kg at the larger scale.