Discover how metabolic engineering of Geobacillus thermoglucosidasius enables high-temperature production of polymer-grade lactic acid for biodegradable plastics
Imagine a world where the plastic bottles, containers, and packaging we use daily could be produced in scorching temperatures that would typically kill most living organisms, all while reducing energy costs and environmental harm. This isn't science fiction—it's the revolutionary promise of high-temperature biomanufacturing using an extraordinary bacterium called Geobacillus thermoglucosidasius.
Through sophisticated metabolic engineering, researchers have transformed G. thermoglucosidasius into an efficient cellular factory that produces polymer-grade lactic acid at an impressive 60°C, potentially transforming the economics of biodegradable plastic production 1 .
The scale of global plastic pollution is staggering—with over 350 million tons produced annually, much of which ends up persisting in ecosystems, harming wildlife, and contaminating food chains 1 .
For large-scale fermentation facilities, even a 5°C increase in operating temperature can save approximately $390,000 annually in cooling costs alone 1 .
Geobacillus thermoglucosidasius is a thermophilic (heat-loving) bacterium that thrives at temperatures between 40-70°C, with an optimal growth range around 60°C 1 . Under these conditions, it grows as robustly as the laboratory workhorse E. coli does at its preferred temperatures 1 .
Optimal Temperature: 60°C
Temperature Range: 40-70°C
Growth Rate: Comparable to E. coli at 37°C
Applications: Lactic acid production, other bioproducts
Introducing and optimizing the enzymatic machinery for lactic acid production 1 .
Removing competing metabolic pathways to increase yield 1 .
Amplifying the cell's lactic acid synthesis capability 1 .
Allowing the engineered strains to optimize their performance through natural selection pressure 1 .
Researchers knocked out the native L-lactate dehydrogenase gene (ldh) and introduced a D-lactate dehydrogenase gene (d-ldh) from Bacillus licheniformis 1 .
The native ldh gene was overexpressed while competing pathways were eliminated to enhance L-lactic acid production 1 .
| Strain | Lactic Acid Type | Production (g/L) | Temperature |
|---|---|---|---|
| GTD17-55 | L-lactic acid | 151.1 | 60°C |
| GTD7-144 | D-lactic acid | 153.1 | 60°C |
The optical purity of the lactic acid produced exceeded 99%, meeting the stringent requirements for polymer-grade PLA production 1 .
While G. thermoglucosidasius shows tremendous promise, researchers continue to explore other microbial hosts with advantageous traits, such as the acid-tolerant yeast Kluyveromyces marxianus 6 .
Despite the exciting progress, challenges remain in scaling up this technology, including optimizing fermentation parameters for industrial-scale reactors and further reducing production costs 5 . Nevertheless, the foundation has been laid for a new generation of industrial biotechnology that operates faster, cleaner, and more efficiently by embracing rather than fighting heat.
The metabolic engineering of Geobacillus thermoglucosidasius represents a perfect marriage of biology and engineering—harnessing the natural heat tolerance of this remarkable bacterium and enhancing it through human ingenuity. By creating microbial factories that produce high-value chemicals at elevated temperatures, scientists have opened a new frontier in sustainable manufacturing.
As research advances, we move closer to a future where the plastics we depend on are derived not from finite fossil fuels, but from renewable resources, processed efficiently by engineered microorganisms working in conditions that would be fatal to their conventional counterparts.