Closed System Thin-Film Bioreactor

At a Glance

Researchers at Colorado State University have developed a cutting-edge bioreactor system that uses thin films of phototrophic microorganisms to produce extracellular chemicals using sunlight and CO₂. This system greatly reduces water and energy needs compared to traditional methods. By immobilizing the microorganisms in a thin layer, this technology enables higher cell density and easier product separation, making the process more sustainable and cost-effective. This advancement holds promise for producing fuels and chemicals, including ammonia.

Background

Phototrophic microorganisms like cyanobacteria and microalgae can convert sunlight and carbon dioxide into valuable chemicals, but current suspension culture methods require large amounts of water, nutrients (to produce biomass, from which the chemicals are obtained), and energy (for mixing, cell separation, and nutrient supply). Additionally, contamination risks and competition for resources with food production limit scalability. This novel thin-film bioreactor system offers a sustainable solution, with improved efficiency and lower resource use.

Overview

The thin-film photomicrobial bioreactor developed by CSU researchers immobilizes phototrophic microorganisms (e.g., cyanobacteria or microalgae) within a thin layer, allowing for high cell densities and optimized light exposure. Unlike traditional suspension cultures, this system requires less water and energy because the microorganisms are held in place, eliminating the need for intensive mixing and separation steps. The reactor can support the production of both volatile and non-volatile extracellular compounds. Volatile products can easily be isolated in the gas phase, while non-volatile products are harvested without significant energy input. By reducing nutrient requirements after initial cell growth, the system also minimizes ongoing nutrient demands, making it highly efficient. This design mitigates contamination risks, allowing continuous operation and improving product yield while reducing the need for constant resource input.

Figure 1. Conceptual illustration of features and advantages of thin-film cultivation in the photomicrobial bioreactor. (A) In standard planktonic cultivations, cell concentrations are low and water use is high. (B) Thin-film cultivation results in higher cell concentrations and lower water use. (C) Thin-film cultivation with cells that secrete products allows for efficient continuous cultivation with simple separation of product from cells.

Figure 2. Growth of cyanobacteria in thin films of a hydrogel. Left: Day 1. Right: Day 10.

Figure 3. Cross-sectional view (10x magnification) of cyanobacteria in a thin hydrogel film after 14 days of cultivation. Light exposure was on the top of the image.

Figure 4. Comparison of thin-film cultivation in two hydrogels (calcium alginate and F127-DMA) to standard planktonic cultivation. Left: Chlorophyll a concentration (a proxy for biomass), illustrating much higher cell concentration in thin-film systems. Right: Productivity of the secreted product trans-cinnamic acid (tCA) on a per-cell basis, indicating that thin-film cells can produce as well or better than planktonic cells. Note that the combination of these plots shows that volumetric productivity (mg tCA/mL·day) is 4–6 fold higher in thin-film cultivations. Asterisks denotes significant differences at p < 0.05.

Benefits

Reduces water and energy consumption compared to suspension cultures
Achieves higher cell density, improving productivity per unit area
Minimizes contamination risks, allowing for more stable, continuous operation
Lowers nutrient demands post-growth phase, reducing overall resource competition
Enables efficient separation and harvesting of both volatile and non-volatile products

Applications

Production of biofuels and other hydrocarbons
Synthesis of ammonia as a sustainable alternative to the Haber-Bosch process
Generation of industrial chemicals from renewable sources
Carbon capture and utilization for sustainable production

Last Updated: February 2025

Opportunity

Available for Exclusive Licensing
TRL: 3

IP Status

US Provisional Patent

Inventors

Ken Reardon
Christie Peebles
Kees Baas
Xingfeng Huang

Reference Number

2025-002

Licensing Manager

Jessy McGowan
Jessy.McGowan@colostate.edu
970-491-7100