Comparison of three screening methods to select mixed-microbial inoculum for mixed-acid fermentations

Area of Science:

• Biotechnology
• Microbiology
• Chemical Engineering

Background:

• The carboxylate platform utilizes mixed microbial cultures to convert biomass into valuable hydrocarbons and chemicals.
• Identifying high-performing inocula is crucial for optimizing carboxylate fermentation efficiency and scalability.

Purpose of the Study:

• To develop and validate a sequential screening method for identifying optimal bacterial inocula for carboxylate fermentation.
• To rank five distinct bacterial communities based on their fermentation performance.

Main Methods:

• A three-tiered sequential screening approach was employed: a 30-day batch fermentation, a 28-day continuum particle distribution model (CPDM), and a 5-month continuous countercurrent fermentation.
• Aseptic techniques were maintained throughout the screening process to ensure reliable results.
• Performance metrics included conversion efficiency, operating map analysis, and continuous fermentation train output.

Main Results:

• Inoculum 1 demonstrated superior performance in the initial 30-day batch fermentation screen, achieving the highest conversion rates.
• The continuum particle distribution model (CPDM) evaluation also identified Inoculum 1 as having the highest performance.
• In continuous countercurrent fermentation, the train inoculated with Inoculum 1 was among the top performers, indicating consistent efficacy.

Conclusions:

• The sequential screening method involving batch, CPDM, and continuous fermentation tests is a predictive and effective approach for selecting optimal inocula.
• Inoculum 1 exhibits significant potential for commercial-scale carboxylate fermentations due to its consistent high performance across all tested conditions.