Experimental research on the spectral complex refractive indices of Chlamydomonas reinhardtii GY-D55 by multi-layer model

The unicellular green alga Chlamydomonas reinhardtii is regarded as a cell factory for the production of recombinant proteins and hydrogen. However, the mainstream adoption has been hindered by simulating light radiative transfer in the photobioreactor accurately, which is influenced by the spectral complex refractive index. To overcome these difficulties, the spectral complex refractive index of Chlamydomonas reinhardtii should be obtained first. In the present study, an experimental method combined with the improved Quantum-behaved Particle Swarm Optimization (IQPSO) algorithm is utilized to retrieve the optical complex refractive indices of Chlamydomonas reinhardtii (C. reinhardtii) GY-D55. The spectral transmittance and reflectance signals are measured by the transmission-reflection measurement system. The forward radiative transfer problem of microalgaes is solved by the finite volume method by considering the light transfer in the wall of the cuvettes. Moreover, the multi-layer model is applied to improve the retrieval accuracy of the results. The investigation shows that this method can be used to obtain the spectral complex refractive indices of C. reinhardtii GY-D55 effectively. The robustness of the retrieved results of imaginary part is better than that of real part.