A bacterium that grows solar panels on itself

"Instead of relying on inefficient chlorophyll to absorb sunlight, we were able to develop a bacterium capable of covering its outer surface with extremely tiny semiconductor nanocrystals," explains Dr. Kelsey K. Sakimoto, editor of the study. "These nanocrystals are much more efficient than chlorophyll and can be produced at a fraction of the cost required to produce solar panels"

[Translation by Dr. Nachmani Moshe]
The process of photosynthesis provides energy for most living things on Earth. However, chlorophyll, the same green pigment in plants that is used to absorb sunlight, is a very inefficient system. In order to allow humans to absorb a greater amount of the sun's energy, scientists have developed bacteria coated with extremely efficient tiny solar panels in order to produce useful compounds.

The researchers presented their research findings at the 254th International Meeting of the American Chemical Society.

"Instead of relying on inefficient chlorophyll to absorb sunlight, we were able to develop a bacterium capable of covering its outer surface with ultra-tiny semiconductor nanocrystals," explains Dr. Kelsey K. Sakimoto, editor of the study. "These nanocrystals are much more efficient than chlorophyll and can be produced at a fraction of the cost required to produce solar panels."

Humanity continues to search for efficient alternatives to fossil fuel as a source of energy and raw materials in the chemical industry. Many scientists have investigated the possibility of developing artificial photosynthesis systems in order to produce renewable energy as well as simple chemical substances while utilizing sunlight. Admittedly, there has been scientific progress in this field, but the systems developed are not efficient enough for the commercial production of fuel and raw materials. Researcher Yang's laboratory at the University of California, Berkeley focuses on the utilization of inorganic semiconductors capable of absorbing the sun's rays and transferring them to organisms such as bacteria, which in turn utilize the energy to produce useful substances from only carbon dioxide and water.

"The core of the research in our laboratory is the possibility of recharging a bacterium that does not perform photosynthesis by supplying energy in the form of electrons from inorganic semiconductors, for example cadmium sulfide, which function as efficient light receptors," said the lead researcher. "We are currently looking for more efficient light absorbing materials than cadmium sulfide in order to charge the bacteria with energy from a light source."

The researchers examined the bacterium Moorella thermoacetica, which occurs in nature and does not carry out photosynthesis, which, as part of its normal respiratory process, produces acetic acid from carbon dioxide. This acid is a versatile chemical from which other important types of substances can be produced, such as fuel, polymers, pharmaceuticals and raw materials for the various industries with the help of genetic engineering of the bacteria. When the bacterium was fed cadmium and the amino acid cysteine, which contains a sulfur atom, the bacterium began to synthesize cadmium sulfide (CdS) nanoparticles on its own, which function as solar panels on its outer surface. The hybrid organism, M. thermoacetica-CdS, produces acetic acid from carbon dioxide, water and light. "Once the bacterium is covered with these tiny solar panels, it is able to synthesize food, fuel and plastic materials, all while utilizing the sun's energy," explains the researcher. "These bacteria are more efficient than photosynthetic plants living in nature." The engineered bacteria works with an efficiency of more than eighty percent, and the process replicates itself so that it is a technology that emits zero waste. "Synthetic biology and the ability to expand the range of products obtained from carbon dioxide reduction will be essential for positioning this technology as an alternative, or one of many alternatives, to the petrochemical industry," explains the lead researcher.

"Existing systems in the field of artificial photosynthesis require the use of solid electrodes, which are a high-cost component. Our biofuel production process obtained from algae is much more competitive, since it utilizes a system of carbon dioxide and sunlight only. At the same time, we are still trying to find the most efficient components in terms of the semiconductor and the type of bacteria. The researcher believes that the hybrid bacteria may have parallels in nature.
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