A team of researchers led by Prof. LI Weiming from the Institute of Applied Ecology of the Chinese Academy of Sciences has developed a novel "coordinated engineering" approach to enhance biofuel production from brown algae, a promising third-generation biomass feedstock. 

Their findings, published on July 22 in the International Journal of Hydrogen Energy, address key metabolic bottlenecks limiting the efficiency of microbial fermentation in marine biorefineries.

Biofuels derived from biomass such as brown algae represent a sustainable solution to the global energy crisis and environmental challenges. Brown algae are considered an ideal third-generation feedstock because they do not compete with food crops and grow rapidly. However, the efficiency of converting this biomass into valuable biofuels has been limited by metabolic bottlenecks within the fermenting microorganisms, a problem hindering the economic viability of marine biorefineries.

To overcome this bottleneck, the researchers introduced the synergistic strategy combining nicotinic acid (NA)—a precursor to NAD synthesis—and nano zero-valent iron (nZVI), which acts as an external electron donor. Using Ethanoligenens harbinense as the model microorganism, this dual supplementation significantly expanded the intracellular NAD pool and increased reducing power.

Under optimized conditions, the combined use of NA and nZVI boosted hydrogen yield by 84.05% and ethanol yield by 81.98% compared to controls, raising the total Bioenergy Conversion Efficiency (BioECE) to 33.57%, an 84.65% improvement.

"Our work reveals a critical principle: the true innovation lies in the synergy. NA provides more carriers, and nZVI provides the extra electrons," said LI Weiming. "This coordinated approach, tailored to the substrate's properties, represents a more sophisticated and adaptable strategy for biofuel production."

Mechanistic analysis confirmed that this strategy upregulated key genes in the NAD synthesis pathway and created a more reducing intracellular environment, which in turn enhanced the activity of key enzymes responsible for hydrogen and ethanol synthesis.

This study highlights the significant potential of combining metabolic cofactor engineering with reducing power supplementation. Future efforts will focus on process optimization to realize the full potential of this strategy within the marine biorefinery concept.

This research was supported by the National Natural Science Foundation of China, the Natural Science Foundation for Excellent Young Scholars of Liaoning Province, and the Science and Technology Agency Livelihood Program of Liaoning Province.

Nicotinic acid (NA) expands the electron carrier pool while nano zero-valent iron (nZVI) provides external electrons, synergistically enhancing hydrogen and ethanol production from brown algae. (Image by LI Weiming et al.)