Enhancing microbial community performance on acid resistance by modified adaptive laboratory evolution.

Area of Science:

• Microbial Biotechnology
• Environmental Microbiology
• Biometallurgy

Background:

• Bioleaching processes rely on microbial consortia for metal extraction.
• Enhancing the efficiency and stability of these consortia is crucial for industrial applications.
• Moderately thermophilic microbial communities are key players in many bioleaching operations.

Purpose of the Study:

• To develop and evaluate a novel three-step adaptive laboratory evolution (ALE) strategy.
• To enhance the bioleaching performance of moderately thermophilic microbial consortia.
• To improve iron oxidation rates and metal recovery from pyrite.

Main Methods:

• A three-step ALE strategy involving consortium construction, directed evolution, and chemostat selection.
• Characterization of the evolved consortium (ALEend) composition using microbial analysis.
• Assessment of ferrous iron oxidation rates and biomass production under specific conditions (pH 0.75).
• Evaluation of community stability under fluctuating culture conditions using Principal Component Analysis (PCA).
• Pyrite bioleaching experiments at varying pH levels (1.5 and 0.75) to quantify iron extraction.

Main Results:

• An improved consortium (ALEend) was obtained, dominated by Leptospirillum ferriphilum (80.32%).
• The ALEend consortium achieved a high ferrous iron oxidation rate (500 mgL⁻¹h⁻¹) and biomass production (2.0 × 10⁸ cells/mL) at pH 0.75.
• Stable ferrous iron oxidation was observed across a wider range of conditions, indicating enhanced community resilience.
• PCA confirmed a stable community structure and reinforced synergistic interactions in the ALEend consortium.
• Pyrite bioleaching showed significantly increased total iron extraction: 26% more at pH 1.5 and 55% more at pH 0.75 compared to the original consortium.

Conclusions:

• The developed three-step ALE strategy is effective in enhancing bioleaching performance.
• The modified microbial community (ALEend) exhibits improved stability and efficiency in iron oxidation and pyrite bioleaching.
• This ALE approach represents a promising strategy for microbial community engineering to optimize bioleaching processes.