Lignocellulosic hydrolysate composition influences contamination profiles in ethanol production

Area of Science:

• Biotechnology
• Microbiology
• Renewable Energy

Background:

• Second-generation ethanol offers a renewable alternative to fossil fuels.
• Microbial contamination poses significant economic and technical challenges to industrial bioethanol production.
• Lignocellulosic inhibitors generated during biomass pretreatment impact fermentation microorganisms.

Purpose of the Study:

• To evaluate the effects of common lignocellulosic inhibitors on Saccharomyces cerevisiae PE-2 and bacterial contaminants.
• To compare the tolerance profiles of yeast and bacteria to various inhibitors.
• To identify strategies for mitigating contamination and enhancing fermentation efficiency.

Main Methods:

• Assessed the growth response of Saccharomyces cerevisiae PE-2, Lactiplantibacillus plantarum I4a, and Limosilactobacillus fermentum I3a to ten lignocellulosic inhibitors.
• Quantified changes in maximum specific growth rate (μmax) under varying inhibitor concentrations.
• Analyzed the differential tolerance of yeast and bacteria to furanic compounds, organic acids, and phenolic compounds.

Main Results:

• Bacteria showed higher resilience to furanic compounds (HMF, furfural) than yeast; these compounds even stimulated bacterial growth.
• Organic acids, especially formic acid, were highly inhibitory to both yeast and bacteria.
• Saccharomyces cerevisiae PE-2 demonstrated greater tolerance to phenolic compounds compared to the tested bacterial strains.

Conclusions:

• Hydrolysate composition significantly influences microbial contamination profiles due to distinct inhibitor tolerances.
• Targeting bacterial contaminants and selecting robust yeast strains are key strategies for improving second-generation ethanol fermentation.
• Addressing microbial contamination is essential for the economic viability of renewable fuel production.