Optimization of Parachlorella kessleri growth under different environmental conditions for lipid production

In the search for materials that do not harm the planet, scientists are turning to the microscopic world of algae. These tiny, single-celled plants use sunlight to grow, and in doing so, they can produce oils and plastics that might one day replace the petroleum-based products that clutter our landfills and oceans. The challenge lies in finding the right kind of algae and the perfect environment to make them grow fast and produce the most useful substances. It is a matter of tuning the conditions—such as the acidity of the water, the warmth of the air, the length of the day, and the amount of carbon dioxide available—much like a gardener adjusting a greenhouse to coax the best harvest from a specific crop. When these factors are balanced correctly, the algae can become a factory for sustainable energy and biodegradable plastics.

A team of researchers in India recently focused on a specific strain of green algae called Parachlorella kessleri, which they discovered in the Yamuna River in Delhi. They wanted to see if this local variety could be coaxed into producing high amounts of lipids, which are fats used to make biofuel, and polyhydroxyalkanoates, or PHAs, which are biodegradable plastics. To find the best recipe for growth, the scientists isolated the algae from the river water and cleaned it of any bacteria. They then grew the algae in glass flasks, carefully changing one condition at a time to see how the tiny cells responded. They tested different levels of acidity, temperatures ranging from cool to hot, various cycles of light and darkness, and different concentrations of carbon dioxide gas bubbled through the water.

The experiments revealed a clear set of conditions where the algae thrived. The cells grew best when the water was slightly alkaline, at a pH of 8, and kept at a comfortable temperature of 25 degrees Celsius. They also preferred a day that was longer than the night, specifically a cycle of 16 hours of light followed by 8 hours of darkness, and they grew most vigorously when the air above them contained 2 percent carbon dioxide. Under these specific conditions, the algae reached their peak size after 16 days. In this optimal environment, the researchers found that the algae were not just growing well; they were also storing energy and building blocks for plastics. The dried cells contained 17 percent lipids and 11 percent PHA by weight. This means that from a single batch of algae grown under these conditions, scientists could potentially harvest both fuel and plastic materials.

This discovery is significant because it is the first time this specific type of algae, found in the Yamuna River, has been studied and optimized for producing both of these valuable materials at the same time. While other studies have looked at how to grow algae for one purpose, this work shows that the same batch of cells can serve a dual purpose, which could make the process of creating sustainable products more efficient and less expensive. The researchers noted that the algae were able to handle a wide range of conditions, but the specific combination of pH, temperature, light, and carbon dioxide they identified produced the highest yield. The study confirms that this indigenous strain has the potential to be used in large-scale operations, such as biorefineries, where it could help create a circular economy by turning waste and sunlight into useful goods. The work lays a foundation for future steps, including testing the algae in larger, more controlled tanks to see if these results hold true on an industrial scale.