Engineering self-flocculating Halomonas campaniensis for wastewaterless open and continuous fermentation

Area of Science:

• Industrial Biotechnology
• Microbial Engineering
• Bioprocess Development

Background:

• Halomonas species offer a robust platform for industrial biotechnology due to their tolerance to high salt and alkaline pH.
• Traditional downstream processing incurs high costs due to continuous centrifugation and saline wastewater treatment.
• Developing sustainable bioprocesses is crucial for reducing environmental impact and operational expenses.

Purpose of the Study:

• To engineer Halomonas campaniensis strain LS21 for self-flocculation to reduce downstream processing costs.
• To develop and evaluate a wastewaterless fermentation strategy for microbial growth and poly-3-hydroxybutyrate (PHB) production.
• To enhance PHB accumulation and overall productivity using optimized genetic elements.

Main Methods:

• Genetic engineering of Halomonas campaniensis LS21 by knocking out the etf operon to induce self-flocculation.
• Development of a wastewaterless fermentation process utilizing the self-flocculating strain.
• Optimization of promoter and ribosome binding sites to enhance PHB production.
• Conducting multiple runs of the wastewaterless process to assess sustainability and efficiency.

Main Results:

• The engineered strain exhibited self-flocculation attributed to decreased surface charge and increased cellular hydrophobicity.
• The wastewaterless fermentation process allowed for rapid cell precipitation and supernatant reuse without sterilization.
• The process was sustained for four runs, generating no wastewater.
• Productivities of cell dry weight and PHB were significantly increased in the wastewaterless continuous process compared to the batch process.

Conclusions:

• Self-flocculating Halomonas offers a viable solution for wastewaterless industrial fermentation.
• The developed strategy effectively reduces wastewater generation and downstream processing costs.
• This approach enhances both cell growth and product formation efficiency, demonstrating significant advantages for sustainable biotechnology.