Transcriptomic analysis unravels the modulating mechanisms of the biomass and value-added bioproducts accumulation by light spectrum in Eustigmatos cf. Polyphem (Eustigmatophyceae)

Effectiveness and associated mechanisms of a combination of biofilm attached cultivation and mixotrophy in promoting microalgal biomass

The effectiveness and associated mechanisms of the biofilm attached cultivation (BAC) under mixotrophy in promoting algal proliferation were investigated. Commercially valuable unicellular microalgae Chromochloris zofingiensis was first used in BAC. Compared with suspended cultivation, the results unequivocally demonstrated the growth benefits of C. zofingiensis cells under BAC with high biomass productivity of 8.53 g m-2 d-1. The physiological and transcriptomic data revealed that the augmented biomass yield was attributable to larger cell size, higher accumulation of chemical substances, significantly upregulated carbon fixation pathway, and greater energy supply efficiency. Here, BAC acts as a "cage" was proposed. Specifically, cells allocate less energy toward mobility, directing a higher share toward growth and production due to their immobilized lifestyle. These findings provide novel insights for optimizing cultivation strategies for commercially valuable algal species and offer a novel perspective from microalgae physiological on understanding higher biomass yield in BAC.

Effects of light quality on microalgae cultivation: bibliometric analysis, mini-review, and regulation approaches

The ever-increasing concern for energy shortages and greenhouse effect has triggered the development of sustainable green technologies. Microalgae have received more attention due to the characteristics of biofuel production and CO2 fixation. From the perspective of autotrophic growth, the optimization of light quality has the potential to promote biomass production and bio-component accumulation in microalgae at low cost. In this study, bibliometric analysis was used to describe the basic features, identify the hotspots, and predict future trends of the research related to the light quality on microalgae cultivation. In addition, a mini-review referring to regulation methods of light quality was provided to optimize the framework of research. Results demonstrated that China has the greatest interest in this area. The destination of most research was to obtain biofuels and high-value-added products. Both blue and red lights were identified as the crucial spectrums for microalgae cultivation. However, sunlight is the most affordable light resource, which could not be fully utilized by microalgae through the photosynthetic process. Hence, some regulation approaches (e.g., dyes, plasmonic scattering, and carbon-based quantum dots) are proposed to increase the proportion of beneficial spectrum for enhancement of photosynthetic efficiency. In summary, this review introduces state-of-the-art research and provides theoretical guidance for light quality optimization in microalgae cultivation to obtain more benefits.

Maximizing fucoxanthin production in Odontella aurita by optimizing the ratio of red and blue light-emitting diodes in an auto-controlled internally illuminated photobioreactor

Fucoxanthin has multiple beneficial effects on human health. However, an efficient cultivation strategy for hyper-production of microalgae-based fucoxanthin has been seldom achieved. Here, an auto-controlled photobioreactor (PBR) installed internal light-emitting diodes illumination with adjustable spectra ratio was firstly used to culture Odontella aurita. The results showed that red light (RL) was more suitable for cell growth and fucoxanthin accumulation than blue light (BL) and white light. The biomass and fucoxanthin production were further promoted by optimizing the ratios of RL and BL, with 8:2 giving the highest productivities of 570 and 9.41 mg L^-1 d^-1, respectively, which is the highest fucoxanthin productivity ever reported under photoautotrophic cultivation. Pilot-scale cultivation demonstrated its promising feasibility in commercial fucoxanthin production. Our study represents a pioneering work of harnessing the PBR with internal illumination for hyper-production of microalgae-based fucoxanthin, and provides feasible strategies for high-efficient production of other value-added products in related species/strains.