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

Abstract

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.

Effect of ultra-violet light radiation on Scenedesmus vacuolatus growth kinetics, metabolic performance, and preliminary biodegradation study

“…The findings in this study were consistent with earlier studies on using UV light radiation for microalgae mutagenesis (Carino et al 2022;Colina et al 2020). The differences in cellular modifications observed in this study compared to other studies can be attributed to the differences in the choice of microalgae species, the length of UV exposure and the operational condition implemented (Carino et al 2022;Choi et al 2017;Colina et al 2020). A shortened lag period and a sharp extended exponential phase was observed for the 24 h UV exposed S. vacuolatus compared with the growth patterns obtained for 2, 4, 6, 12, 48 h UV exposed S. vacuolatus and the wild S. vacuolatus.…”

Strain Development in Microalgal Biotechnology—Random Mutagenesis Techniques

“…Several dyes, such as SYTOX Green [ 30 , 31 ], propidium iodide [ 32 ], methylene blue, trypan blue, eosin and nile blue [ 29 ], have been applied so far. Most studies aim for a survival rate of 5–20% to reach a good mutation rate within the surviving cell population [ 33 , 34 , 35 ].…”

Arthrospira platensis Mutagenesis for Protein and C-Phycocyanin Improvement and Proteomics Approaches

“…Mutagenesis is one of the most widely studied methods for increasing biomass and lipid content in microalgae. Random mutagenesis can be achieved through chemical mutagens, including ethyl methanesulphonate (EMS), N-methyl-N -nitro-N-nitrosoguanidine (MNNG), N-methyl-N-nitrosourea and diethyl sulphate (DES) [21,24,48]. Base pairing mistakes, purine deamination, transitions, transversions and frameshift mutations are all caused by chemicals [21].…”

“…Random mutagenesis can be achieved through chemical mutagens, including ethyl methanesulphonate (EMS), N-methyl-N -nitro-N-nitrosoguanidine (MNNG), N-methyl-N-nitrosourea and diethyl sulphate (DES) [21,24,48]. Base pairing mistakes, purine deamination, transitions, transversions and frameshift mutations are all caused by chemicals [21]. DES is a monofunctional alkylating chemical that has been demonstrated in a variety of organisms to cause mutations, chromosomal abnormalities and other genetic changes [48].…”

“…Mutagenesis is simple and affordable, requiring little understanding of an organism's genetic information, metabolic processes and genetic control. It also involves minimal technological modifications and the strains produced are not subject to rigorous legal issues [21]. Various microalgae have been randomly mutated using both chemical and physical mutagenesis to enhance their growth rates and metabolite yield (lipid) and also increase their toxic compound tolerance against environmental stress [22].…”