pH adjustment increases biofuel production from inhibitory switchgrass hydrolysates

Area of Science:

• Biomass Conversion
• Renewable Energy
• Microbial Fermentation

Background:

• Lignocellulosic biomass like switchgrass is a sustainable source for biofuels.
• Drought conditions increase inhibitory compounds in switchgrass, hindering microbial biofuel conversion.
• Engineered yeasts like Saccharomyces cerevisiae and bacteria like Zymomonas mobilis are used for biofuel production.

Purpose of the Study:

• To investigate methods for alleviating inhibition in drought-stressed switchgrass hydrolysates.
• To optimize fermentation conditions for improved biofuel yield from switchgrass.
• To enhance the efficiency of converting lignocellulosic biomass into biofuels.

Main Methods:

• Comparing Ammonia Fiber Expansion (AFEX) and Soaking in Aqueous Ammonia (SAA) pretreatment methods.
• Adjusting the pH of switchgrass hydrolysates to assess its impact on fermentation.
• Utilizing engineered Saccharomyces cerevisiae and Zymomonas mobilis for fermentation experiments.
• Employing a synthetic mimic of switchgrass hydrolysate to identify inhibitory mechanisms.

Main Results:

• Fermentation rates and ethanol production were higher at pH 5.8 compared to pH 5.0 for both yeast and bacteria.
• SAA pretreatment resulted in higher fermentation rates and titers than AFEX pretreatment for drought-stressed switchgrass.
• pH adjustment above 5.0 relieved inhibition caused by lignocellulose-derived compounds in hydrolysates.

Conclusions:

• SAA pretreatment and pH 5.8 significantly enhance biofuel production from switchgrass hydrolysates, especially under drought conditions.
• Alleviating pH-dependent inhibition is crucial for improving microbial biofuel conversion from lignocellulosic biomass.
• Optimized pretreatment and pH control offer a viable strategy for industrial biofuel production from stressed biomass.