Monochromatic Light Management for Bioeconomic Production of Metabolites in the Soil Microalga Pleurastrum insigne

Microalgae represent a promising raw material for the bioeconomy and biotechnology. One of the key factors regulating their metabolism is light. However, the traditional approach to cultivation, aimed at maximising biomass productivity due to high lighting intensity, contradicts the principles of energy efficiency. In addition, the responses of soil microalgae to the spectral composition of light remain poorly understood, which creates a gap in fundamental knowledge. The Pleurastrum insigne CAMU MZ–Ch4 soil strain is a potent producer of valuable compounds. Physico-chemical and instrumental analysis, including spectrophotometric, chromatographic and gravimetric techniques, were used to determine the productive and biochemical parameters of the strain. It was shown that blue and red light with intensities of 90 and 150 µmol m−2 s−1 are optimal in absolute terms for the growth and CO2 biofixation, green light for the accumulation of pigments and antioxidants, and low-intensity red light is the most energy efficient for the synthesis of lipids and other metabolites. Based on calculations of product-specific energy intensity, it was demonstrated that the “more light = more product” strategy increases metabolite energy intensity. Maximum bioeconomic efficiency (the minimum cost of electricity to produce a unit of a metabolite) is achieved with low intensity of red and blue light.