Design a novel internally illuminated mirror photobioreactor to improve microalgae production through homogeneous light distribution

Enhanced carbon capture and utilization in transgenic Chlorella sorokiniana harboring pyridoxal kinase under dynamic carbon dioxide levels

Microalgae are crucial in carbon capture, utilization, and storage due to the efficient CO2 assimilation through photosynthesis and potential for high-value biochemical production. However, limited research has explored genetic strain to enhance carbon capture under dynamic CO2 conditions. This research aimed to optimize carbon capture in Chlorella sorokiniana by introducing pyridoxal kinase (pdxY) and cultivation in fluctuating CO2 concentrations. The sequential optimization successfully led to 34% increase in growth with improved carbon capture efficiency to 88.5%. Transgenic strains 2023PY and BSLPY demonstrated superior performance under high (2%) and low (0.04%) CO2, respectively. Addition of Tris base to the medium stabilized pH at favorable level, which is crucial for optimum growth. Scale-up cultivation in 2-L photobioreactor achieved net-zero carbon emissions across all strains. These findings highlight the potential of genetic engineering and process optimization in advancing microalgal carbon capture, along with the production of protein, starch, and lipid for sustainable applications.

SL-6 Mimic Is a Biostimulant for Chlorella sorokiniana and Enhances the Plant Biostimulant Effect of Microalgal Extract

This study aimed to evaluate the impact of a more cost-efficient strigolactone mimic SL-6 on Chlorella sorokiniana NIVA-CHL 176 growth in comparison with the strigolactone analog GR24 and the plant biostimulant functions of microalgal extracts. Three molar SL-6 concentrations were tested: 10-7 M, 10-8 M, and 10-9 M, respectively. Five parameters of microalgal growth were assessed: optical density, turbidity, biomass production, chlorophyll fluorescence, and pigment concentration. Results after 15 days of culturing revealed that the SL-6 treatments significantly enhanced biomass production (13.53% at 10-9 M), pigment synthesis, and photosystem II activity (14.38% at 10-9 M). The highest increases in pigments induced by SL-6 were 15.7% for chlorophyll a (at 10-8 M SL-6), 12.87% for chlorophyll b (at 10-9 M SL-6), 2.3% for carotenoids (at 10-8 M SL-6), and 10.78% for total pigments (at 10-8 M SL-6) per gram biomass compared to the solvent control (DMSO). Higher doses of GR24 and SL-6 (10-7 M) inhibited microalgal growth, reducing cell density, biomass production, and pigment synthesis. The microalgal extracts acted as plant biostimulants, stimulating root and shoot elongation and proton pump functioning of mung seedlings in the presence and absence of salt stress. The extracts from SL-6 biostimulated C. sorokiniana were more active as plant biostimulants than the extracts from the non-stimulated C. sorokiniana.

A Comparative Analysis Assessing Growth Dynamics of Locally Isolated Chlorella sorokiniana and Chlorella vulgaris for Biomass and Lipid Production with Biodiesel Potential

Prior research has emphasized the potential of microalgae in biodiesel production, driven by their ability to replace fossil fuels. However, the significant costs associated with microalgae cultivation present a major obstacle to scaling up production. This study aims to develop an eco-friendly microalgae cultivation system by integrating carbon dioxide from flue gas emissions with an affordable photobioreactor, providing a sustainable biomass production. The research evaluates the growth performance of Chlorella sorokiniana and Chlorella vulgaris across this integrated system for biomass and lipid production. Results indicate substantial biomass yields of 1.97 and 1.84 g/L, with lipid contents of 35 % and 41 % for C. sorokiniana and C. vulgaris, respectively. The macrobubble photobioreactor demonstrates high potential for microalgae biomass and lipid production, yielding quality fatty acid methyl esters such as palmitic, linoleic and stearic. This study presents an environmentally friendly system for efficient microalgae cultivation, generating lipid-rich biomass suitable for biodiesel production.

Blue-light irradiation induced partial nitrification

The role of ray radiation from the sunlight acting on organisms has long-term been investigated. However, how the light with different wavelengths affects nitrification and the involved nitrifiers are still elusive. Here, we found more than 60 % of differentially expressed genes (DEGs) in nitrifiers were observed under irradiation of blue light with wavelengths of 440-480 nm, which were 13.4 % and 20.3 % under red light and white light irradiation respectively. Blue light was more helpful to achieve partial nitrification rather than white light or red light, where ammonium oxidization by ammonia-oxidizing archaea (AOA) with the increased relative abundance from 8.6 % to 14.2 % played a vital role. This was further evidenced by the enhanced TCA cycle, reactive oxygen species (ROS) scavenge and DNA repair capacity in AOA under blue-light irradiation. In contrast, nitrite-oxidizing bacteria (NOB) was inhibited severely to achieve partial nitrification, and the newly discovered encoded blue light photoreceptor proteins made them more sensitive to blue light and hindered cell activity. Ammonia-oxidizing bacteria (AOB) expressed genes for DNA repair capacity under blue-light irradiation, which ensured their tiny impact by light irradiation. This study provided valuable insights into the photosensitivity mechanism of nitrifiers and shed light on the diverse regulatory by light with different radiation wavelengths in artificial systems, broadening our comprehension of the nitrogen cycle on earth.