Use of an immobilised thermostable -CA (SspCA) for enhancing the metabolic efficiency of the freshwater green microalga .

There is significant interest in increasing the microalgal efficiency for producing high-quality products that are commonly used as food additives in nutraceuticals. Some natural substances that can be extracted from algae include lipids, carbohydrates, proteins, carotenoids, long-chain polyunsaturated fatty acids, and vitamins. Generally, microalgal photoautotrophic growth can be maximised by optimising CO biofixation, and by adding sodium bicarbonate and specific bacteria to the microalgal culture. Recently, to enhance CO biofixation, a thermostable carbonic anhydrase (SspCA) encoded by the genome of the bacterium has been heterologously expressed and immobilised on the surfaces of bacteria. Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous metalloenzymes, which catalyse the physiologically reversible reaction of carbon dioxide hydration to bicarbonate and protons: CO + HO ⇄ HCO + H. Herein, we demonstrate for the first time that the fragments of bacterial membranes containing immobilised SspCA (M-SspCA) on their surfaces can be doped into the microalgal culture of the green unicellular alga, , to significantly enhance the biomass, photosynthetic activity, carotenoids production, and CA activity by this alga. These results are of biotechnological interest because is widely used in many different areas, including photosynthesis research, human pharmaceutical production, aquaculture-based food production, and wastewater treatment.