Enhanced lipid content in Chlorella sp. FC2 IITG via high energy irradiation mutagenesis

Analysis of oil accumulation mechanisms in plasma induced mutant Scenedesmus strains compared to original Scenedesmus strains

Scenedesmus sp. is a species of the Scenedesmus genus within the phylum Chlorophyta, commonly found as a planktonic algal species in freshwater and known for its rapid growth rate. This study employs room-temperature, atmospheric-pressure plasma mutagenesis for the breeding of Scenedesmus sp., utilizing transcriptomic analysis to investigate the biosynthesis mechanism of triglycerides. Further analysis of differentially expressed genes in transcriptome by measuring the macroscopic biological indicators of mutant and original algal strains. The findings of the study suggest that the mutant strain's photosynthesis has been enhanced, leading to improved light energy utilization and CO2 fixation, thereby providing more carbon storage and energy for biomass and lipid production. The intensification of glycolysis and the TCA (tricarboxylic acid) cycle results in a greater shift in carbon flux towards lipid accumulation. An elevated expression level of related enzymes in starch and protein degradation pathways may enhance acetyl CoA accumulation, facilitating a larger substrate supply for fatty acid production and thereby increasing lipid yield.

Characterization of isolated UV-C-irradiated mutants of microalga Chlorella vulgaris for future biofuel application

Microalgae-based biofuel is considered as one of the most promising sources of alternative energy because it is sustainable and does not pose threats to the environment and food security. However, attempts in improving microalgal strains to attain the ideal characteristics for biofuel application are yet to unravel. In this study, random UV-C mutagenesis was employed to generate starch-deficient mutants of indigenous Chlorella vulgaris to enhance its productivity. Out of 872 colonies, two isolated mutants (cvm5 and cvm6) were isolated and showed significant increase in cell concentrations by > 1.47-fold and > 1.04-fold, respectively. However, mutant cells exhibited smaller in size which might contributed to the significant decrease in their biomass. Moreover, gathered data revealed that the total lipid content of cvm5 was enhanced significantly (75%, > 1.3-fold increase). Additionally, triacylglycerol (TAG) content of the said mutant constitutes 48% of the dry cell weight (DCW) while cvm6 consist of 41% of the DCW. These promising and novel findings suggest that the two generated and isolated mutants are good candidates for future commercial biofuel production, especially in the Philippines. In addition, these findings may contribute on the prior knowledge of the usage of UV-C for microalgal strain development.

Harnessing the Power of Mutagenesis and Adaptive Laboratory Evolution for High Lipid Production by Oleaginous Microalgae and Yeasts

Oleaginous microalgae and yeasts represent promising candidates for large-scale production of lipids, which can be utilized for production of drop-in biofuels, nutraceuticals, pigments, and cosmetics. However, low lipid productivity and costly downstream processing continue to hamper the commercial deployment of oleaginous microorganisms. Strain improvement can play an essential role in the development of such industrial microorganisms by increasing lipid production and hence reducing production costs. The main means of strain improvement are random mutagenesis, adaptive laboratory evolution (ALE), and rational genetic engineering. Among these, random mutagenesis and ALE are straight forward, low-cost, and do not require thorough knowledge of the microorganism’s genetic composition. This paper reviews available mutagenesis and ALE techniques and screening methods to effectively select for oleaginous microalgae and yeasts with enhanced lipid yield and understand the alterations caused to metabolic pathways, which could subsequently serve as the basis for further targeted genetic engineering.